Drug-drug interactions among recently hospitalised patients – frequent but mostly clinically insignificant

Potential Drug Interactions in Terminally-Ill Cancer Patients, a Report from the Middle East

This study aims to evaluate the epidemiology of potential drug interactions in terminally-ill cancer patients receiving exclusively supportive care. In this cross-sectional study, during a 6-month follow-up, we considered the medical record of terminally-ill cancer patients referred to palliative care at the cancer center in Isfahan, Iran. Potential drug-drug interactions (DDIs) were assessed by Lexi-Interact ver.1.1 online software. During the study period, 133 terminally-ill cancer patients were recruited. We detected 1678 DDIs with moderate or major severity levels. Among them, 330, 219, 32, 1075, and 51 interactions were categorized in B, C, D, and X drug interactions categories, respectively. One hundred and twenty-two patients (91.73%) encountered at least one potential drug-drug interaction during the end of life care. Mechanistically, most drug-drug interactions (64.5%) were pharmacodynamics. The most frequent pharmacological class of drugs responsible for DDIs were quetiapine (91 cases), oxycodone (87 cases), and sertraline (55 cases). Interaction between oxycodone and sertraline was found to be in the top 10 detected DDIs (13.7%). Our results showed that potentially moderate or major drug-drug interactions often occur among terminally-ill cancer patients and the clinical significance of DDIs should be considered meticulously in the palliative care cancer setting.

Drug-Drug-Gene Interactions in Cardiovascular Medicine

Cardiovascular disease remains a leading cause of both morbidity and mortality worldwide. It is widely accepted that both concomitant medications (drug-drug interactions, DDIs) and genomic factors (drug-gene interactions, DGIs) can influence cardiovascular drug-related efficacy and safety outcomes. Although thousands of DDI and DGI (aka pharmacogenomic) studies have been published to date, the literature on drug-drug-gene interactions (DDGIs, cumulative effects of DDIs and DGIs) remains scarce. Moreover, multimorbidity is common in cardiovascular disease patients and is often associated with polypharmacy, which increases the likelihood of clinically relevant drug-related interactions. These, in turn, can lead to reduced drug efficacy, medication-related harm (adverse drug reactions, longer hospitalizations, mortality) and increased healthcare costs. To examine the extent to which DDGIs and other interactions influence efficacy and safety outcomes in the field of cardiovascular medicine, we review current evidence in the field. We describe the different categories of DDIs and DGIs before illustrating how these two interact to produce DDGIs and other complex interactions. We provide examples of studies that have reported the prevalence of clinically relevant interactions and the most implicated cardiovascular medicines before outlining the challenges associated with dealing with these interactions in clinical practice. Finally, we provide recommendations on how to manage the challenges including but not limited to expanding the scope of drug information compendia, interaction databases and clinical implementation guidelines (to include clinically relevant DDGIs and other complex interactions) and work towards their harmonization; better use of electronic decision support tools; using big data and novel computational techniques; using clinically relevant endpoints, preemptive genotyping; ensuring ethnic diversity; and upskilling of clinicians in pharmacogenomics and personalized medicine.

Drug interactions in hospital prescriptions in Denmark: Prevalence and associations with adverse outcomes

Purpose

While the beneficial effects of medications are numerous, drug–drug interactions may lead to adverse drug reactions that are preventable causes of morbidity and mortality. Our goal was to quantify the prevalence of potential drug–drug interactions in drug prescriptions at Danish hospitals, estimate the risk of adverse outcomes associated with discouraged drug combinations, and highlight the patient types (defined by the primary diagnosis of the admission) that appear to be more affected.

Methods

This cross‐sectional (descriptive part) and cohort study (adverse outcomes part) used hospital electronic health records from two Danish regions (~2.5 million people) from January 2008 through June 2016. We included all inpatients receiving two or more medications during their admission and considered concomitant prescriptions of potentially interacting drugs as per the Danish Drug Interaction Database. We measured the prevalence of potential drug–drug interactions in general and discouraged drug pairs in particular during admissions and associations with adverse outcomes: post‐discharge all‐cause mortality rate, readmission rate and length‐of‐stay.

Results

Among 2 886 227 hospital admissions (945 475 patients; median age 62 years [IQR: 41–74]; 54% female; median number of drugs 7 [IQR: 4–11]), patients in 1 836 170 admissions were exposed to at least one potential drug–drug interaction (659 525 patients; median age 65 years [IQR: 49–77]; 54% female; median number of drugs 9 [IQR: 6–13]) and in 27 605 admissions to a discouraged drug pair (18 192 patients; median age 68 years [IQR: 58–77]; female 46%; median number of drugs 16 [IQR: 11–22]). Meropenem‐valproic acid (HR: 1.5, 95% CI: 1.1–1.9), domperidone‐fluconazole (HR: 2.5, 95% CI: 2.1–3.1), imipramine‐terbinafine (HR: 3.8, 95% CI: 1.2–12), agomelatine‐ciprofloxacin (HR: 2.6, 95% CI: 1.3–5.5), clarithromycin‐quetiapine (HR: 1.7, 95% CI: 1.1–2.7) and piroxicam‐warfarin (HR: 3.4, 95% CI: 1–11.4) were associated with elevated mortality. Confidence interval bounds of pairs associated with readmission were close to 1; length‐of‐stay results were inconclusive.

Conclusions

Well‐described potential drug–drug interactions are still missed and alerts at point of prescription may reduce the risk of harming patients; prescribing clinicians should be alert when using strong inhibitor/inducer drugs (i.e. clarithromycin, valproic acid, terbinafine) and prevalent anticoagulants (i.e. warfarin and non‐steroidal anti‐inflammatory drugs ‐ NSAIDs) due to their great potential for dangerous interactions. The most prominent CYP isoenzyme involved in mortality and readmission rates was 3A4.

The Prevalence of Potential Drug-Drug Interactions in CKD-A Retrospective Observational Study of Cerrahpasa Nephrology Unit

Background and Objectives: Chronic kidney disease (CKD) is usually linked with polypharmacy and patients are invariably at risk of complex medication regimens. The present study was designed to estimate the potential drug-drug interactions (pDDIs) through the prescription patterns provided to patients of the Nephrology Transplant Unit of Cerrahpasa Medical Faculty patients. Materials and Methods: 96 patients were included in the study. pDDIs among every combination of the prescribed drug were analyzed using the Thomson Reuters Micromedex. Results: We found 149 pDDIs making 2.16 interactions per prescription with incidence rates of 69.7%. Approximately 4.1% of interactions were of significant severity, 75.1% moderate severity, and 20.8% were classified as minor pDDIs. The most frequent interactions were found between iron and aluminum, calcium or magnesium-containing products (21.37%), calcium channel blockers and beta-blockers (8.96%); and aspirin and aluminum, calcium, or magnesium-containing products (7.58%). We identified 42 drug pairs with probability of clinical significance. The most commonly reported clinical outcomes of the pDDIs were hypo- or hypertension (39.24%), decreased drug efficacy (24.05%), and arrhythmia (9.49%). Aluminum, calcium, or magnesium-containing drug products (33.10%) constituted the primary class of drugs involved in interactions. Conclusions: This study showed pharmacodynamics (49%), pharmacokinetics (42.94%) interactions, polypharmacy and gender as determinant of pDDIs. A comprehensive multicenter research is required to decrease the morbidity and ease the state burden.

The Role of Food Supplementation in Microcirculation-A Comprehensive Review

(1) Background: Cardiovascular disease (CVD) is a major public health concern worldwide and a key cause of morbidity and mortality in developed countries. Accumulating evidence shows that several CVD forms are characterized by significant microcirculatory dysfunction, which may both cause and be caused by macrovascular disease, often preceding clinical manifestations by several years. Therefore, interest in exploring food supplements to prevent and restore microcirculation has grown. Given the continuous need to expand the available therapeutic arsenal for CVD, the food supplements market has recently grown and is expected to continue growing. (2) Methods: We provide an authoritative up-to-date comprehensive review of the impact of food supplementation on microcirculation by analyzing the European and American legal food supplements framework and the importance of food safety/food quality in this industry. We review the main literature about food bioactive compounds with a focus on microcirculation and some main food supplements with proven benefits. (3) Results: Despite a lack of scientific evidence, diet and microcirculatory function are clearly connected. The main food supplement examples in the literature with potential beneficial effects on microcirculation are: Ruscus aculeatus L., Centella asiatica L., Ginkgo biloba L., Salvia miltiorrhiza Bunge, Crataegus spp., Ginseng, Mangifera indica L., Aesculus hippocastanum L., Hamamelis virginiana L., and Vitis vinifera L. (4) Conclusions: Further clinical trials are necessary to better explore the effects of these food supplements.

Assessment of potential drug interactions among psychiatric inpatients receiving antipsychotic therapy of a secondary care hospital, United Arab Emirates

The majority of the antipsychotic drugs are also known to interact with other co-administered drugs. Drug-drug interaction (DDI) reports among patients receiving antipsychotic medications are common. The study aims to identify the potential drug-drug, drug-tobacco, and drug-ethanol interactions associated with antipsychotics and significant predictors of potential DDIs (pDDIs). A prospective observational study was conducted among psychiatric inpatients receiving antipsychotic therapy and met the inclusion criteria that were reviewed for the presence of pDDIs using DRUGDEX-Micromedex database 2.0. The identified pDDIs were graded according to the severity and type of documentation. A total of 110 patients had a minimum of a single interaction, and the overall frequency of pDDIs reported was 64.7%. Of 158 pDDIs, 92 interactions (58.2%) were of major severity, while 66 interactions were of moderate severity (41.8%). Olanzapine with valproate (40 [25.3%]) was the most commonly documented pDDIs, followed by risperidone with valproate (20 [12.6%]). Olanzapine with tobacco (20 [69%]) was the most common drug-tobacco interaction. Simultaneously, olanzapine with ethanol was the most common potential drug and ethanol interaction (9 [50%]). Variables such as the number of drugs and polypharmacy statistically significantly predicted pDDIs (F[7, 162] = 8.155, P < 0.05, R² = 0.26). Knowing the severity of different pDDIs will help clinicians and prescribers monitor patient safety through regular monitoring for interactions and adverse drug effects in future. The number of medications and polypharmacy was found to be the most significant predictor of pDDIs.

Prevalence of potential drug-drug interactions in breast cancer patients and determination of their risk factors

Breast cancer patients use numerous medications, which include cytotoxic chemotherapy drugs, hormonal agents and supportive medication, so they are more vulnerable to potential adverse drug interactions. This study aimed to evaluate frequency, severity, clinical importance and risk factors responsible for the Drug-drug interactions (DDIs) in a cohort of patients suffering from breast cancer. Data was obtained from 150 patients in the oncology ward (both inpatient and outpatient) with a confirmed diagnosis of breast cancer and currently receiving standard breast cancer-directed treatment. The data was recorded into a pre-designed form specifically made for this study through individual patient interviews and by reviewing the detailed medical chart records of the patients. DDIs were identified by using drug interaction software such as Medscape mobile application and Micromedex version 2.The results of this study showed that all patients were female. The mean numbers of drugs that patients used were 7. Potential drug interactions were identified in 92% of the patients. When drug groups were overviewed, 32% of interactions were between anti neoplastic drugs, 62.9% interactions were between the anti neoplastic agent and supportive care drugs and 5% of them were between anti-cancer drugs and drugs used to treat comorbidities. Major DDIs were found in 62.2% of patients, 25.3% of DDIs were moderate and 12.4% were minor. The number of drugs, comorbid diseases, and selection of chemo protocols were the risk factors for drug interactions. Most of the DDIs found in breast cancer therapy may have adverse consequences on patient health and therapeutic outcomes. Therefore, health care professionals should review the medication regimen of patients with breast cancer before starting any chemotherapy treatment.

Prevalence and nature of potential drug-drug interactions among hospitalized HIV patients presenting with suspected meningitis in Uganda

Background

Management of co-infections including cryptococcal meningitis, tuberculosis and other opportunistic infections in persons living with HIV can lead to complex polypharmacotherapy and increased susceptibility to drug-drug interactions (DDIs). Here we characterize the frequency and types of potential DDIs (pDDIs) in hospitalized HIV patients presenting with suspected cryptococcal or tuberculous meningitis.

Methods

In a retrospective review of three cryptococcal meningitis trials between 2010 and 2017 in Kampala, Uganda, medications received over hospitalization were documented and pDDI events were assessed. IBM Micromedex DRUGDEX® online drug reference system was used to identify and describe potential interactions as either contraindicated, major, moderate or minor. For antiretroviral DDIs, the Liverpool Drug Interactions Checker from the University of Liverpool was also used to further describe interactions observed.

Results

In 1074 patients with suspected meningitis, pDDIs were present in 959 (overall prevalence = 89.3%) during the analyzed 30 day window. In total, 278 unique interacting drug pairs were identified resulting in 4582 pDDI events. Of all patients included in this study there was a mean frequency of 4.27 pDDIs per patient. Of the 4582 pDDI events, 11.3% contraindicated, 66.4% major, 17.4% moderate and 5% minor pDDIs were observed. Among all pDDIs identified, the most prevalent drugs implicated were fluconazole (58.4%), co-trimoxazole (25.7%), efavirenz (15.6%) and rifampin (10.2%). Twenty-one percent of the contraindicated pDDIs and 27% of the major ones involved an antiretroviral drug. Increased likelihood of QT interval prolongation was the most frequent potential clinical outcome. Dissonance in drug interaction checkers was noted requiring clinicians to consult more than one database in making clinical decisions about drug combinations.

Conclusions

The overall prevalence of pDDIs in this population is high. An understanding of drug combinations likely to result in undesired clinical outcomes, such as QT interval prolongation, is paramount. This is especially important in resource limited settings where availability of therapeutic drug monitoring and laboratory follow-up are inconsistent. Adequate quantification of the increased likelihood of adverse clinical outcomes from multiple drug-drug interactions of the same kind in a single patient is needed to aid clinical decisions in this setting.

High Risk of Drug-drug interactions among Hospitalized Patients with kidney Diseases at a Nigerian Teaching Hospital: A Call for Action

Background

Potential drug-drug interactions (DDIs) are increasingly common in clinical practice, especially among individuals with chronic conditions, such as chronic kidney dysfunction. However, data relating to DDIs among chronically ill patients are limited in Nigeria. We, therefore, investigated the prevalence and pattern of DDIs among patients with kidney diseases on admission at a tertiary hospital in Lagos, Nigeria.

Materials and Methods

This was a prospective observational study involving 61 adults with kidney diseases and on admission in medical wards of the study center, over a 3-month period. Data extractions were with a purposefully designed pro forma to extract relevant data on demographic, clinical, and dosing regimens of the prescribed drugs for individual patients. Potential DDIs were identified, and their severity was rated using the MICROMEDEX^® software database (IBM^® Watson-Truven Health Analytics), which is available online with limited access.

Results

Of the 61 patients evaluated, majority were males (34; 55.7%), were elderly (26; 42.6%), and had chronic kidney disease Stage 3 (40; 65.5%). The most common cause of kidney disease was hypertension (20; 32.8%). Out of the 542 prescriptions received by the patients, potential DDI was observed in 508 (93.7%) prescriptions. Clinically significant drug interactions (CSDIs) were detected in 486 (85.7%) prescriptions. Pharmacodynamic DDIs (466; 91.7%) were the most common. Pill burden exceeding 25 pills/day was present in nine (14.8%) patients. The severities of the potential DDIs were major (135; 24.9%), moderate (333; 61.4%), and minor (38; 7.1%). Only two different potential DDIs were rated X (contraindicated).

Conclusion

Exposure to drugs with potential DDIs was very common among patients with kidney diseases. Most of the CSDIs observed were of major severity. The use of DDI checker before prescribing drugs for individuals with kidney diseases could avert clinically significant interactions.

Effects of Phenothiazines on Aldehyde Oxidase Activity Towards Aldehydes and N-Heterocycles: an In Vitro and In Silico Study

BACKGROUND

Aldehyde oxidase (AOX) is an important molybdenum-containing enzyme with high similarity with xanthine oxidase (XO). AOX involved in the metabolism of a large array of aldehydes and N-heterocyclic compounds and its activity is highly substrate-dependent.

OBJECTIVES

The aim of this work was to study the effect of five important phenothiazine drugs on AOX activity using benzaldehyde and phenanthridine as aldehyde and N-heterocyclic substrates, respectively.

METHODS

The effect of trifluperazine, chlorpromazine, perphenazine, thioridazine and promethazine on rat liver AOX was measured spectrophotometrically. To predict the mode of interactions between the studied compounds and AOX, a combination of homology modeling and a molecular docking study was performed.

RESULTS

All phenothiazines could inhibit AOX activity measured either by phenanthridine or benzaldehyde with almost no effect on XO activity. In the case of benzaldehyde oxidation, the lowest and highest half-maximal inhibitory concentration (IC₅₀) values were obtained for promethazine (IC₅₀ = 0.9 µM), and trifluoperazine (IC₅₀ = 3.9 µM), respectively; whereas perphenazine (IC₅₀ = 4.3 µM), and trifluoperazine (IC₅₀ = 49.6 µM) showed the strongest and weakest inhibitory activity against AOX-catalyzed phenanthridine oxidation, respectively. The in silico findings revealed that the binding site of thioridazine is near the dimer interference, and that hydrophobic interactions are of great importance in all the tested phenothiazines.

CONCLUSION

The five studied phenothiazine drugs showed dual inhibitory effects on AOX activity towards aldehydes and N-heterocycles as two major classes of enzyme substrates. Most of the interactions between the phenothiazine-related drugs and AOX in the binding pocket showed a hydrophobic nature.

Potential Drug-drug Interactions at a Referral Pediatric Oncology Ward in Iran: A Cross-sectional Study

Incidence of drug-drug interactions (DDIs) has been widely reported; however, such reports in pediatric oncology patients still remain scarce. We studied frequency and demographic correlates of moderate and major DDIs at a pediatric oncology ward in Isfahan, Iran. All pediatric oncology patients admitted to the Omid hospital during a 6-month period (2017) who received at least 2 anticancer or non-anticancer drugs concomitantly were included in our study. Potential DDIs between anticancer and non-anticancer drugs during hospitalization was identified using Lexi-Interact on-line software. We detected 194 DDIs with moderate or major severity for our included 115 patients. Mechanistically, most of DDIs (56.4%) were pharmacodynamic. Systematic use of corticosteroids (82.0%), antimetabolites (77.0%), and antiemetic drugs (69.5%) were the most frequent medication classes responsible for detected DDIs. The interaction between aminoglycosides and the third generation cephalosporins was the most common (13.9%) non-anticancer DDI. The only identified interaction between 2 anticancer drugs was doxorubicin with cyclophosphamide. Age, sex, and the number of administered medications were associated with DDIs. Potential moderate or major DDIs occur frequently among pediatric cancer patients. More studies are needed to assess clinical and economic implications of DDIs in pediatric oncology patients.

Clinical Implications of P-Glycoprotein Modulation in Drug-Drug Interactions

Drug-drug interactions (DDIs) occur commonly and may lead to severe adverse drug reactions if not handled appropriately. Considerable information to support clinical decision making regarding potential DDIs is available in the literature and through various systems providing electronic decision support for healthcare providers. The challenge for the prescribing physician lies in sorting out the evidence and identifying those drugs for which potential interactions are likely to become clinically manifest. P-glycoprotein (P-gp) is a drug transporting protein that is found in the plasma membranes in cells of barrier and elimination organs, and plays a role in drug absorption and excretion. Increasingly, P-gp has been acknowledged as an important player in potential DDIs and a growing body of information on the role of this transporter in DDIs has become available from research and from the drug approval process. This has led to a clear need for a comprehensive review of P-gp-mediated DDIs with a focus on highlighting the drugs that are likely to lead to clinically relevant DDIs. The objective of this review is to provide information for identifying and interpreting evidence of P-gp-mediated DDIs and to suggest a classification for individual drugs based on both in vitro and in vivo evidence (substrates, inhibitors and inducers). Further, various ways of handling potential DDIs in clinical practice are described and exemplified in relation to drugs interfering with P-gp.

Comparative analysis of three drug-drug interaction screening systems against probable clinically relevant drug-drug interactions: a prospective cohort study

PURPOSE

Drug-drug interaction (DDI) screening systems report potential DDIs. This study aimed to find the prevalence of probable DDI-related adverse drug reactions (ADRs) and compare the clinical usefulness of different DDI screening systems to prevent or warn against these ADRs.

METHODS

A prospective cohort study was conducted in patients urgently admitted to medical departments. Potential DDIs were checked using Complete Drug Interaction®, Lexicomp® Online™, and Drug Interaction Checker®. The study team identified the patients with probable clinically relevant DDI-related ADRs on admission, the causality of which was assessed using the Drug Interaction Probability Scale (DIPS). Sensitivity, specificity, and positive and negative predictive values of screening systems to prevent or warn against probable DDI-related ADRs were evaluated.

RESULTS

Overall, 50 probable clinically relevant DDI-related ADRs were found in 37 out of 795 included patients taking at least two drugs, most common of them were bleeding, hyperkalemia, digitalis toxicity, and hypotension. Complete Drug Interaction showed the best sensitivity (0.76) for actual DDI-related ADRs, followed by Lexicomp Online (0.50), and Drug Interaction Checker (0.40). Complete Drug Interaction and Drug Interaction Checker had positive predictive values of 0.07; Lexicomp Online had 0.04. We found no difference in specificity and negative predictive values among these systems.

CONCLUSION

DDI screening systems differ significantly in their ability to detect probable clinically relevant DDI-related ADRs in terms of sensitivity and positive predictive value.

Adverse effects of plant food supplements and botanical preparations: a systematic review with critical evaluation of causality

AIMS

The objective of this review was to collect available data on the following: (i) adverse effects observed in humans from the intake of plant food supplements or botanical preparations; (ii) the misidentification of poisonous plants; and (iii) interactions between plant food supplements/botanicals and conventional drugs or nutrients.

METHODS

PubMed/MEDLINE and Embase were searched from database inception to June 2014, using the terms 'adverse effect/s', 'poisoning/s', 'plant food supplement/s', 'misidentification/s' and 'interaction/s' in combination with the relevant plant name. All papers were critically evaluated according to the World Health Organization Guidelines for causality assessment.

RESULTS

Data were obtained for 66 plants that are common ingredients of plant food supplements; of the 492 papers selected, 402 (81.7%) dealt with adverse effects directly associated with the botanical and 89 (18.1%) concerned interactions with conventional drugs. Only one case was associated with misidentification. Adverse effects were reported for 39 of the 66 botanical substances searched. Of the total references, 86.6% were associated with 14 plants, including Glycine max/soybean (19.3%), Glycyrrhiza glabra/liquorice (12.2%), Camellia sinensis/green tea ( 8.7%) and Ginkgo biloba/gingko (8.5%).

CONCLUSIONS

Considering the length of time examined and the number of plants included in the review, it is remarkable that: (i) the adverse effects due to botanical ingredients were relatively infrequent, if assessed for causality; and (ii) the number of severe clinical reactions was very limited, but some fatal cases have been described. Data presented in this review were assessed for quality in order to make the results maximally useful for clinicians in identifying or excluding deleterious effects of botanicals.

Analysis of drug interactions at the end of life

BACKGROUND

As death approaches, patients are at their most frail, but an increasing symptom burden often necessitates an increase in medications, putting them at higher risk for drug-drug interactions.

OBJECTIVES

To assess the potential for drug-drug interactions in routine prescribing at the end of life.

METHODS

An Australian retrospective multicentre case-note review of 266 consecutive adult patients who were referred to specialist palliative care, with data available on 166. Medications used in the last 2 weeks of life were screened for potential interactions using the 'Stockley's Drug Interactions' software.

RESULTS

The mean number of medications prescribed was 10.8, median 9 (IQR 6-14); all patients received at least one medication. In this study, 72% of patients were at risk of 1 or more potential drug-drug interaction. The mean number of potential interactions was 4.4, with a median of 2.5 (IQR 0-7) per patient. There were only 4/166 (2.4%) prescribed medications with an associated clinical record of an adverse drug reaction.

CONCLUSIONS

Potential drug-drug interactions are common for this group of patients. Some interactions may be recognised as an acceptable risk when the prescription is written. Further research is necessary to determine the best way to improve recognition of potential drug-drug interactions and the rates of morbidity or accelerated mortality associated with this. It is likely that palliative care services will need to implement multiple strategies including greater use of computerised prescribing software, and greater closer liaison with clinical pharmacists.

How common are drug and gene interactions? Prevalence in a sample of 1143 patients with CYP2C9, CYP2C19 and CYP2D6 genotyping

AIM

Drug-drug interactions (DDIs) are a widely recognized major cause of adverse drug reactions, but two other newly described important types of interactions also exist: drug-gene interactions (DGIs) and drug-drug-gene interactions (DDGIs). A drug-gene interaction occurs when a patient's genetic CYP450 type (e.g., CYP2D6 poor metabolizer) affects that patient's ability to clear a drug. A drug-drug-gene interaction occurs when the patient's CYP450 genotype and another drug in the patient's regimen (e.g., a CYP2D6 inhibitor) affect that individual's ability to clear a drug. Their prevalence has not been previously described. This pilot study investigates the frequency of DDIs, DGIs and DDGIs in a sample of CYP450 tested individuals.

MATERIALS & METHODS

The investigators conducted a retrospective analysis of 1143 individuals with known CYP2D6, CYP2C19 and CYP2C9 genotypes. Using the individuals' medication lists and YouScript(®), a software tool to analyze cumulative DDIs and DGIs, the prevalence of DDI, DGI and DDGIs was analyzed.

RESULTS

A total of 1053 potential major or substantial interactions were identified in 501 individuals. DDIs accounted for 66.1% of the total interactions. The remaining 33.9% of interactions were DGIs (14.7%) and DDGIs (19.2%). When compared with DDIs alone, DGIs and DDGIs increased the total number of potentially clinically significant interactions by 51.3%.

CONCLUSION

In the future, identifying DGIs and DDGIs may lead to a more comprehensive method of identifying individuals who are at risk for adverse drug reactions.

Understanding and preventing drug-drug and drug-gene interactions

Concomitant administration of multiple drugs can lead to unanticipated drug interactions and resultant adverse drug events with their associated costs. A more thorough understanding of the different cytochrome P450 isoenzymes and drug transporters has led to new methods to try to predict and prevent clinically relevant drug interactions. There is also an increased recognition of the need to identify the impact of pharmacogenetic polymorphisms on drug interactions. More stringent regulatory requirements have evolved for industry to classify cytochrome inhibitors and inducers, test the effect of drug interactions in the presence of polymorphic enzymes, and evaluate multiple potentially interacting drugs simultaneously. In clinical practice, drug alert software programs have been developed. This review discusses drug interaction mechanisms and strategies for screening and minimizing exposure to drug interactions. We also provide future perspectives for reducing the risk of clinically significant drug interactions.

Drug-drug interactions in inpatient and outpatient settings in Iran: a systematic review of the literature

Drug-drug interactions (DDIs) are an important type of adverse drug events. Yet overall incidence and pattern of DDIs in Iran has not been well documented and little information is available about the strategies that have been used for their prevention. The purpose of this study was to systematically review the literature on the incidence and pattern of DDIs in Iran as well as the used strategies for their prevention. PubMed, Scopus, electronic Persian databases, and Google Scholar were searched to identify published studies on DDIs in Iran. Additionally, the reference lists of all retrieved articles were reviewed to identify additional relevant articles. Eligible studies were those that analyzed original data on the incidence of DDIs in inpatient or outpatient settings in Iran. Articles about one specific DDI and drug interactions with herbs, diseases, and nutrients were excluded. The quality of included studies was assessed using quality assessment criteria. Database searches yielded 1053 potentially eligible citations. After removing duplicates, screening titles and abstracts, and reading full texts, 34 articles were found to be relevant. The quality assessment of the included studies showed a relatively poor quality. In terms of study setting, 18 and 16 studies have been conducted in inpatient and outpatient settings, respectively. All studies focused on potential DDIs while no study assessed actual DDIs. The median incidence of potential DDIs in outpatient settings was 8.5% per prescription while it was 19.2% in inpatient settings. The most indicated factor influencing DDIs incidence was patient age. The most involved drug classes in DDIs were beta blockers, angiotensin-converting-enzyme inhibitors (ACEIs), diuretic agents, and non-steroidal anti-inflammatory drugs (NSAIDs). Thirty-one studies were observational and three were experimental in which the strategies to reduce DDIs were applied. Although almost all studies concluded that the incidence of potential DDIs in Iran in both inpatient and outpatient settings was relatively high, there is still no evidence of the incidence of actual DDIs. More extensive research is needed to identify and minimize factors associated with incidence of DDIs, and to evaluate the effects of preventive interventions especially those that utilize information technology.

Actual drug-drug interactions in elderly patients discharged from internal medicine clinic: a prospective observational study

PURPOSE

The aim of the study was to evaluate the incidence and type of actual drug-drug interactions (DDIs) that result in adverse drug reactions (ADRs) or diminished therapeutic effect in elderly patients within 30 days of discharge from an internal medicine clinic.

METHODS

A prospective observational study was conducted at the Internal Medicine Clinic of University Hospital Dubrava, Zagreb, Croatia, between October and December 2011. Patients aged ≥ 65 years discharged from the Internal Medicine Clinic during the study period with a prescription for two or more medications were eligible for inclusion in the study. A total of 222 patients were ultimately enrolled in the study. For each patient, potential DDIs were identified using Lexi-Interact software. The follow-up visit was scheduled approximately 30 days after discharge. Causality between DDIs and ADRs or diminished therapeutic effect of drugs was assessed by two independent clinicians.

RESULTS

Potential DDIs were identified in 190 (85.6 %) patients. Actual DDIs were detected in 21 (9.5 %) patients. In 19 patients, DDIs resulted in an ADR. Diminished therapeutic effect resulting from DDIs was detected in two patients. Angiotensin-converting enzyme inhibitors were the drug class most frequently associated with DDI-related ADRs.

CONCLUSIONS

A significant incidence of actual DDIs suggests that DDIs play an important role in patient safety. Drug therapy should be initiated if absolutely necessary, and the number of drugs used to treat elderly patients should be minimized to reduce the incidence of DDI-related adverse patient outcomes.

Potential drug-drug interactions at a referral hematology-oncology ward in Iran: a cross-sectional study

PURPOSE

To assess the pattern and probable risk factors for moderate and major drug-drug interactions in a referral hematology-oncology ward in Iran.

METHODS

All patients admitted to hematology-oncology ward of Dr. Shariati Hospital during a 6-month period and received at least two anti-cancer or non-anti-cancer medications simultaneously were included. All being scheduled anti-cancer and non-anti-cancer medications both prescribed and administered during ward stay were considered for drug-drug interaction screening by Lexi-Interact On-Desktop software.

RESULTS

One hundred and eighty-five drug-drug interactions with moderate or major severity were detected from 83 patients. Most of drug-drug interactions (69.73 %) were classified as pharmacokinetics. Fluconazole (25.95 %) was the most commonly offending medication in drug-drug interactions. Interaction of sulfamethoxazole-trimethoprim with fluconazole was the most common drug-drug interaction (27.27 %). Vincristine with imatinib was the only identified interaction between two anti-cancer agents. The number of administered medications during ward stay was considered as an independent risk factor for developing a drug-drug interaction.

CONCLUSIONS

Potential moderate or major drug-drug interactions occur frequently in patients with hematological malignancies or related diseases. Performing larger standard studies are required to assess the real clinical and economical effects of drug-drug interactions on patients with hematological and non-hematological malignancies.

Characterisation of non-warfarin-associated bleeding events reported to the Norwegian spontaneous reporting system

OBJECTIVE

The aim of the study was to analyse non-warfarin-associated bleeding adverse drug events reported to the Norwegian spontaneous reporting system, with characterisation of the bleeding locations, outcome and drug interactions. In addition, concordance in assessments between reporters and evaluators, trend shifts in reporting, and detection of potentially new adverse drug interaction signals were studied.

METHODS

Data on bleeding events reported between 1 January 2003 and 31 December 2005 were retrieved from the Norwegian spontaneous reporting system database.

RESULTS

Of 327 case reports of non-warfarin-associated bleeding events, 270 reports (82.6 %) were characterised as serious and 69 (21.1 %) had a fatal outcome. One hundred and eighty-seven bleeds (57.5 %) were gastrointestinal, 57 (17.4 %) were cerebral, and 81 (24.8 %) were from other bleeding sites. The bleeding sites differed with respect to the patient's age, drug use, diagnoses and outcomes. Of drugs associated with bleeding, nonsteroidal anti-inflammatory drugs (NSAIDs)/COX-2 inhibitors (145 reports) and acetylsalicylic acid (128 reports) were most frequently used. Only fibrinolytics were associated with increased mortality. There was a 67.4 % correlation between reporters and evaluators in assessment of drugs associated with bleeding (P < 0.001), with considerable variation in concordance between drug groups.

CONCLUSION

Non-warfarin-associated bleeding events are associated with substantial mortality. Old age, cerebral bleeds, number of drugs used, and use of fibrinolytics are all independently associated with increased mortality. The recognition of the bleeding risk of commonly used drugs such as acetylsalicylic acid and heparins may be insufficient among prescribers.

Prevalence of potential drug-drug interactions in cancer patients treated with oral anticancer drugs

BACKGROUND

Potential drug-drug interactions (PDDIs) in patients with cancer are common, but have not previously been quantified for oral anticancer treatment. We assessed the prevalence and seriousness of potential PDDIs among ambulatory cancer patients on oral anticancer treatment.

METHODS

A search was conducted in a computer-based medication prescription system for dispensing oral anticancer drugs to outpatients in three Dutch centres. Potential drug-drug interactions were identified using electronic (Drug Interaction Fact software) and manual screening methods (peer-reviewed reports).

RESULTS

In the 898 patients included in the study, 1359 PDDIs were identified in 426 patients (46%, 95% confidence interval (CI)=42-50%). In 143 patients (16%), a major PDDI was identified. The drug classes most frequently involved in a major PDDI were coumarins and opioids. The majority of cases concerned central nervous system interactions, PDDIs that can cause gastrointestinal toxicity and prolongation of QT intervals. In multivariate analysis, concomitant use of more drugs (odds ratio (OR)=1.66, 95% CI=1.54-1.78, P<0001) and genito-urinary cancer (OR=0.25, 95% CI=0.12-0.52, P<0001) were risk factors.

CONCLUSION

Potential drug-drug interactions are very common among cancer patients on oral cancer therapy. Physicians and pharmacists should be more aware of these potential interactions.

Assessment of Drug-Drug Interactions among Renal Failure Patients of Nephrology Ward in a South Indian Tertiary Care Hospital

Polypharmacy is common in drug prescriptions of chronic kidney disease patients. A study of the prescription patterns of drugs with potential interactions would be of interest to prevent drug related adverse events. A prospective observational study of six months (Dec 2009-May 2010) was carried out among the chronic kidney disease patients admitted to the nephrology ward of a South Indian tertiary care hospital. The pattern and rates of drug-drug interactions seen in the prescriptions of these patients was studied. Among the 205 prescriptions included, a total of 474 interactions were reported, making 2.7 interactions per prescription with incidence rates of 76.09%. Around 19.62% of interactions were of major severity. Most common interactions were found between ascorbic acid and cyanocobalamine (12.45%), clonidine and metoprolol (3.80%) respectively. Hypo or hypertension (31.65%), decreased drug efficacy (29.11%) and hypo or hyperglycemia (14.14%), were the most commonly reported clinical outcomes of the drug interactions. Cardiovascular drugs (calcium channel blockers and beta blockers; 52%) constitute the major class of drugs involved in interactions. As most of the interactions had a delayed onset, long term follow-up is essential to predict the clinically significant outcomes of these interactions. Hence, drug interactions are commonly seen in the prescriptions of chronic kidney disease patients which can lead to serious adverse events if not detected early. Need for collaboration with a clinical pharmacist and electronic surveillance, which are absent in developing countries like India, is emphatic.

Prevalence of drug interactions in hospital healthcare

AIM OF THE REVIEW

To study the prevalence of drug interactions in hospital healthcare by reviewing literature.

METHOD

A review was carried out of studies written in Spanish and English on the prevalence of drug interactions in hospital care published in Pubmed between January 1990 and September 2008. The search strategy combined free text and MeSH terms, using the following keywords: "Drug interaction", "prevalence" and "hospital". For each article, we classified independent variables (pathology, age of population, whether patients were hospitalized or not, geographical location, etc.) and dependent variables (number of interactions per 100 patients studied, prevalence of patients with interactions, most common drug interactions, and others).

RESULTS

The search generated 436 articles. Finally, 47 articles were selected for the study, 3 provided results about drug interactions with real clinical consequences, 42 about potential interactions, and 2 described both. The prevalence of patients with interactions was between 15 and 45 % and the number of interactions per 100 patients was between 37 and 106, depending on the group of studies analyzed. There was a considerable increase in these rates in patients with heart diseases and elderly persons.

CONCLUSION

There is a large number of studies on the prevalence of drug interactions in hospitals but they report widely varying results. The prevalence is higher in patients with heart diseases and elderly people.

Inappropriate prescribing for older people admitted to an intermediate-care nursing home unit and hospital wards

OBJECTIVE

To identify inappropriate prescribing among older patients on admission to and discharge from an intermediate-care nursing home unit and hospital wards, and to compare changes during stay within and between these groups.

DESIGN

Observational study.

SETTING AND SUBJECTS

Altogether 400 community-dwelling people aged ≥ 70 years, on consecutive emergency admittance to hospital wards of internal medicine and orthopaedic surgery, were randomized to an intermediate-care nursing home unit or hospital wards; 290 (157 at the intermediate-care nursing home unit and 133 in hospital wards) were eligible for this sub-study.

MAIN OUTCOME MEASURES

Prevalence on admission and discharge of potentially inappropriate medications (Norwegian general practice [NORGEP] criteria) and drug-drug interactions; changes during stay.

RESULTS

The mean (SD) age was 84.7 (6.2) years; 71% were women. From admission to discharge, the mean numbers of drugs prescribed per person increased from 6.0 (3.3) to 9.3 (3.8), p < 0.01. The prevalence of potentially inappropriate medications increased from 24% to 35%, p < 0.01; concomitant use of ≥ 3 psychotropic/opioid drugs and drug combinations including non-steroid anti-inflammatory drugs (NSAIDs) increased significantly. Serious drug-drug interactions were scarce both on admission and discharge (0.7%).

CONCLUSIONS

Inappropriate prescribing was prevalent among older people acutely admitted to hospital, and the prevalence was not reduced during stay at an intermediate-care nursing home unit specially designed for these patients.

Out-patients Prescriptions are Safe from Drug Interactions or Not: A Pilot Study Report

The objective of the research work was to analysis the out patients drug interactions and alerts the healthcare professionals to prevent the future complications. The study was done in three pharmacies within a 200 meters distance of each other. The doctors involved were made aware of the study but data were collected without their knowledge. All prescriptions presented to the three pharmacies were analyzed during the five-month study period. A total of 500 prescriptions were analyzed and 64 drug-drug interactions were detected giving a drug-drug interaction rate of 12.8 percent but 436 (87.2%) prescriptions are free from drug interactions. Moderate drug interactions were found in 10.2%, Severe were 2.6% and contraindicated were 0% and also disease wise drug interaction analysis were carried out during the study results, more number of drug interactions reported in central nerves system followed by diabetes mellitus. Outpatient visits resulted in minimal numbers of clinically important drug-drug interactions, these interactions can have significant implications due to medication-related morbidity and mortality. Pharmacists can play a critical role in managing the medication therapy of patients at risk for clinically important drug-drug interactions.

Evaluation of drug-drug interaction screening software combined with pharmacist intervention

BACKGROUND

Drug-drug interactions (DDI) in hospitalized patients are highly prevalent and an important source of adverse drug reactions. DI computerized screening system can prevent the occurrence of some of these events.

OBJECTIVE

To evaluate the impact of drug-drug interaction (DDI) screening software combined with active intervention in preventing drug interactions.

SETTING

The study was conducted at General Hospital of Vitória da Conquista (HGVC), Brazil.

METHOD

A quasi-experimental study was used to evaluate the impact of IM-Pharma, a locally developed drug-drug interaction screening system, coupled with pharmacist intervention on adverse drug events in the hospital setting.

MAIN OUTCOME MEASURE

The proportion of patients co-prescribed two interacting drugs were measured in two phases, prior the implementation of IM-Pharma and during the intervention period. DDI rates per 100 patient days were calculated before and after implementation. Risk ratios were estimated by Poisson regression models.

RESULTS

A total of 6,834 instances of drug-drug interactions were identified; there was an average of 3.3 DDIs per patient in phase one and 2.5 in phase two, a reduction of 24 % (P = 0.03). There was a 71 % reduction in high-severity drug-drug interaction (P < 0.01). The risk for all DDIs decreased 50 % after the implementation of IM-Pharma (P < 0.01), and for those with high-severity, the reduction was 81 % (P < 0.01).

CONCLUSION

The performance of IM-Pharma combined with pharmacist intervention was positive with an expressive reduction in the risk of DDIs.

Pharmacy students' retention of knowledge of drug-drug interactions

OBJECTIVES

To evaluate pharmacy students' drug-drug interaction (DDI) knowledge retention over 1 year and to determine whether presenting DDI vignettes increased knowledge retention.

METHODS

A knowledge assessment tool was distributed to fourth-year pharmacy students before and after completing a DDI educational session. The questionnaire was re-administered after 1 year to assess knowledge retention. During the intervening year, students had the option of presenting DDI case vignettes to preceptors and other health professionals as part of their advanced pharmacy practice experiences (APPEs).

RESULTS

Thirty-four of 78 pharmacy students completed both the post-intervention and 1-year follow-up assessments. Students' knowledge of 4 DDI pairs improved, knowledge of 3 DDI pairs did not change, and knowledge of the remainder of DDI pairs decreased. Average scores of the 18 students who completed all tests and presented at least 1 vignette during their APPEs were higher on the 1-year follow-up assessment than students who did not, suggesting greater DDI knowledge retention (p = 0.04).

CONCLUSION

Although pharmacy students' overall DDI knowledge decreased in the year following an educational session, those who presented vignettes to health professionals retained more DDI knowledge, particularly on those DDIs for which they gave presentations. Other methods to enhance pharmacy students' retention of DDI knowledge of clinically important DDIs are needed.

Potential drug-drug interactions associated with prolonged stays in the intensive care unit: a retrospective cohort study

BACKGROUND AND OBJECTIVES

Drug-drug interactions (DDIs) are one cause of adverse drug events and can cause harm to hospitalized patients. Little has been done to study the relationship between potential DDIs and an increased length of stay (LOS) in the intensive care unit (ICU). The aim of this study was to determine the frequency of potential DDIs during ICU stays and to determine whether the frequency of these adverse events was associated with ICU LOS.

METHODS

This retrospective cohort study was conducted from January to December 2007 in the ICU of the General Hospital of Vitória da Conquista, Brazil. The study population comprised all patients aged >18 years admitted to the hospital's ICU. Demographic and prescription data were collected from medical files. All prescriptions administered during the period were examined. Potential DDIs were identified and classified according to the book Drug Interaction Facts. The median LOS was determined by the Kaplan-Meier method and Cox proportional hazards models were fitted to analyse the relationship between potential DDIs and the LOS.

RESULTS

The study population comprised 236 adults, 158 (67%) of them men, between the ages of 18 and 96 years, with a mean ± SD age of 50 ± 20 years. The median LOS among patients with at least one DDI was 12 days compared with 5 days among those with no DDIs (p < 0.01). Multiple Cox proportional regression analyses showed that a prolonged ICU stay was positively associated with DDIs (hazard ratio [HR] 0.54; 95% CI 0.37, 0.80; p < 0.01), where an HR <1 indicates a variable that increases the risk of prolonged stay (i.e. an adverse outcome). This association was true even after controlling for the cost of hospitalization, the number of procedures and the number of prescribed drugs.

CONCLUSION

In this study, DDIs were found to be associated with a longer ICU stay. Given that LOS is an important indicator of the quality of health care delivered and that DDIs are considered avoidable, specific measures are necessary to increase the recognition of DDIs. E-prescriptions and dispensing programmes associated with a DDI knowledge base can help health professionals identify hazardous drug combinations.

Identifying adverse drug reactions associated with drug-drug interactions: data mining of a spontaneous reporting database in Italy

BACKGROUND

Drug-drug interactions (DDIs) are an important cause of adverse drug reactions (ADRs). Many studies have recently considered this issue, but most of them focus only on potential interactions and are often related to the hospital setting. A spontaneous reporting database could be a valuable resource for detection of ADRs associated with DDIs; however, data in the literature are limited.

OBJECTIVE

To detect those patients treated with potentially interacting drugs and the cases where reported adverse reactions are a possible consequence of DDIs, using an Italian spontaneous reporting database.

METHODS

The data were obtained from a database containing all reports of suspected ADRs from five Italian regions (January 1990 to December 2007) that are the main contributors to the Italian spontaneous reporting system. All reports containing at least two drugs, reported as being suspected of causing the ADR or as concomitant medication, were selected and a list of drug pairs was drawn up. We performed a search to verify which drug pairs are considered a potential DDI, using the Internet version of the DRUGDEX(R) system. For each report containing a potential DDI, we verified whether the description of the adverse reaction corresponded to the interaction effect.

RESULTS

The database contained 45 315 reports, of which 17 700 (39.1%) had at least two reported drugs. We identified 5345 (30.2%) reports with potential DDIs, and in 1159 (21.7%) of these reports a related ADR was reported. The percentage of reports with potential DDIs increased in relation to the number of concomitantly administered drugs, ranging from 9.8% for two drugs to 88.3% for eight or more drugs. The percentages of serious or fatal reports of ADRs associated with a DDI were significantly higher than other reports analysed. The mean age, percentage of male patients and the mean number of drugs were also significantly higher in reports with DDIs than in other reports. In 235 of 1159 reports (20.3%), both interacting drugs were recognized as suspect by the reporter. This percentage varies in relation to the drugs involved, ranging from 2% to about 65%. The most frequently reported interaction was digoxin and diuretics, but no fatal ADRs were reported with this combination. The combination of anticoagulant and antiplatelet agents was responsible for the greatest number of serious reactions and deaths.

CONCLUSIONS

This study validates that spontaneous reporting, despite its limitations, can be an important resource for detecting ADRs associated with the concomitant use of interacting drugs. Moreover, our data confirm that DDIs could be a real problem in clinical practice, showing that more than one in five patients exposed to a potential DDI experienced a related ADR.

Potential drug interactions in cancer therapy: a prevalence study using an advanced screening method

BACKGROUND

In cancer patients, drug interactions may intensify adverse events or reduce antitumour effects. We assessed the prevalence of potential drug interactions (PDIs) among ambulatory cancer patients on i.v. treatment using an advanced screening method.

PATIENTS AND METHODS

Data on drugs used for comorbidities, anticancer agents, over-the-counter (OTC) drugs, and comorbidities were collected by means of a structured interview among the patients and review of medical charts. PDIs were identified using electronic (Drug Interaction Facts software, version 4.0) and manual screening methods (peer-reviewed reports).

RESULTS

In this study, 278 patients were enrolled. We identified 348 PDIs. Of all patients, 161 (58%) had at least one PDI. Of all PDIs, 34% was classified as major and 60% as moderate. Coumarins, quinolones, antiepileptics, and hydrochlorothiazide were frequently part of a PDI. Interactions that potentially cause QT interval prolongation, gastrointestinal toxicity, and central nervous system depression were also common. In multivariate analysis, an increasing number of drugs [odds ratio (OR) = 1.4, confidence interval (CI) 1.23-1.52; P < 0.001] and the use of an OTC drug (OR = 0.56, CI 0.32-0.97; P = 0.045) were risk factors.

CONCLUSIONS

PDIs are common in patients treated for an (haemato-) oncological disease. Screening for potential interactions should take place routinely before administering chemotherapy.

Potential drug interactions and duplicate prescriptions among ambulatory cancer patients: a prevalence study using an advanced screening method

BACKGROUND

The pharmacotherapeutic treatment of patients with cancer is generally associated with multiple side-effects. Drug interactions and duplicate prescriptions between anti-cancer drugs or interactions with medication to treat comorbidity can reinforce or intensify side-effects.The aim of the present study is to gain more insight into the prevalence of drug interactions and duplicate prescriptions among patients being treated in the outpatient day care departments for oncology and hematological illnesses. For the first time the prevalence of drug interactions with OTC-drugs in cancer patients will be studied. Possible risk factors for the occurrence of these drug-related problems will also be studied.

METHODS/DESIGN

A multicenter cross-sectional observational study of the epidemiology of drug interactions and duplicate prescriptions is performed among all oncology and hemato-oncology patients treated with systemic anti-cancer drugs at the oncology and hematology outpatient day care department of the VU University medical center and the Zaans Medical Center.

DISCUSSION

In this article the prevalence of potential drug interactions in outpatient day-care patients treated with anti-cancer agents is studied using a novel more extensive screening method. If this study shows a high prevalence of drug interactions clinical pharmacists and oncologists must collaborate to develop a pharmaceutical screening programme, including an automated electronic warning system, to support drug prescribing for ambulatory cancer patient. This programme could minimize the occurrence of drug related problems such as drug interactions and duplicate prescriptions, thereby increasing quality of life.

TRIAL REGISTRATION

This study is registered, number NTR2238.

The incidence of potential drug-drug interactions in elderly patients with arterial hypertension

OBJECTIVE

To assess the incidence and type of potential, clinically significant drug-drug interactions in elderly outpatients with arterial hypertension.

SETTING

Three community pharmacies in Croatia.

METHOD

Eligible patients were aged 65 or older, treated for arterial hypertension and received 2 or more drugs. Potential interactions were identified by Lexi-Interact software. The software categorized each potential interaction according to clinical significance in five groups: (A) No known interaction; (B) Specified agents may interact, but there is little to no evidence of clinical concern; (C) Specified agents may interact in a clinically significant manner. Monitoring therapy is suggested; (D) The two medications may interact in a clinically significant manner. Modification of therapy is suggested; (X) Contraindicated combination. Interactions of level C, D and X were considered clinically significant.

MAIN OUTCOME MEASURE

The incidence and type of potential drug-drug interactions.

RESULTS

There were 265 patients included in the study. Potential, clinically significant drug interactions were identified in 240 (90.6%) patients, out of which 97.9% had interactions with clinical significance C, 20.4% D, and 0.8% X. The median number of drug interactions per patient was 4. We identified 215 drug combinations with the potential to cause clinically significant interaction, out of which 83.3% had clinical significance C, 16.3% clinical significance D, and 0.4% clinical significance X.

CONCLUSION

Drug-drug interactions are common in elderly hypertensive patients. Computer-based screening could help pharmacists and physicians to recognize potential, clinically significant interactions.

Drug treatment in an ageing population: practical implications

The population of the industrialised nations is ageing. By 2020 those of 65 years and older will constitute nearly 17% of the US population; it is predicted that the proportion of the population aged 80 years and over will then range from 3.5 to 6.5%, around the world. Those over 65, due to age-related chronic disease and more prophylactic prescribing, receive a disproportionate number of drugs; in the UK for example, 45% of the total prescriptions dispensed. Older patients may benefit from prophylactic treatments to a greater extent than younger people because of a higher absolute risk of disease and it is therefore important that they are not inappropriately denied these. However, it is also important that, as each additional drug prescribed brings an increased risk of an adverse drug effect, prescribers have enough knowledge of pharmacological issues in old age to enable them to weigh up these conflicting pressures to arrive at good prescribing decisions.

The effect of systematic medication review in elderly patients admitted to an acute ward of internal medicine

Elderly patients are vulnerable to medication errors and adverse drug events due to increased morbidity, polypharmacy and inappropriate interactions. The objective of this study was to investigate whether systematic medication review and counselling performed by a clinical pharmacist and clinical pharmacologist would reduce length of in-hospital stay in elderly patients admitted to an acute ward of internal medicine. A randomized, controlled study of 100 patients aged 70 years or older was conducted in an acute ward of internal medicine in Denmark. Intervention arm: a clinical pharmacist conducted systematic medication reviews after an experienced medical physician had prescribed the patients' medication. Information was collected from medical charts, interview with the patients and database registrations of drug purchase. Subsequently, medication histories were conferred with a clinical pharmacologist and advisory notes recommending medication changes were completed. Physicians were not obliged to comply with the recommendations. Control arm: medication was reviewed by usual routine in the ward. Primary end-point was length of in-hospital stay. In addition, readmissions, mortality, contact to primary healthcare and quality of life were measured at 3-month follow-up. In the intervention arm, the mean length of in-hospital stay was 239.9 hr (95% CI: 190.2-289.6) and in the control arm: 238.6 hr (95% CI: 137.6-339.6), which was neither a statistical significant nor a clinically relevant difference. Moreover, no differences were observed for any of the secondary end-points. Systematic medication review and medication counselling did not show any effect on in-hospital length of stay in elderly patients when admitted to an acute ward of internal medicine.

Evaluation of risk factor management of patients treated on an internal nephrology ward: a pilot study

Background

The objectives of this pilot study were to evaluate treatment quality for the risk factors of hypertension, diabetes and hyperlipidemia as well as the overall treatment quality for patients on an internal nephrology ward. This evaluation included the collection of data concerning the quality of therapeutic drug monitoring, drug use and potential drug-drug interactions. Establishing such baseline information highlights areas that have a need for further therapeutic intervention and creates a foundation for improving patient care, a subject that could be addressed in future clinical pharmacy research projects.

Methods

Medical charts of patients treated on a single internal nephrology ward were retrospectively evaluated using a predefined data collection form. Assessment of further need for therapeutic intervention was performed.

Results

For 76.5% (n = 78) of the total study population (n = 102), there was either a possibility (39.2%, n = 40) or a need (37.3%, n = 38) for further intervention based on the overall assessment. For the risk factors of hypertension, diabetes and hyperlipidemia, the proportions of patients that require further intervention were 78.8% (n = 71), 90.6% (n = 58) and 87.9% (n = 58), respectively. Patients with diabetes or hyperlipidemia were less likely to have optimal risk factor control. The number of drugs prescribed and the number of potential drug-drug interactions were significantly higher after in-hospital treatment.

Conclusion

Risk factor treatment needs optimisation. Risk factor management, systematic medication reviews, and screening for and management of potential drug-drug interactions deserve great attention. Clinical pharmacy services could help in the achievement of treatment goals.

Incidence of risk factors for developing hyperkalemia when using ACE inhibitors in cardiovascular diseases

STUDY OBJECTIVE

To determine the incidence of and the risk factors associated with hyperkalemia, induced by ACEI-drug interactions among cardiac patients.

SETTING

Five medical and cardiology wards of a tertiary care center in Malaysia.

SUBJECTS

Five hundred cardiac inpatients, who received ACEIs concomitantly with other interacting drugs.

METHOD

This was a prospective cohort study of 500 patients with cardiovascular diseases admitted to Penang Hospital between January to August 2006, who received ACEIs concomitantly with other interacting drugs. ACEI-drug interactions of clinical significance were identified using available drug information resources. Drug Interaction Probability Scale (DIPS) was used to assess the causality of association between ACEI-drug interactions and the adverse outcome (hyperkalemia).

MAIN OUTCOME MEASURE

Hyperkalemia as an adverse clinical outcome of the interaction was identified from laboratory investigations.

RESULTS

Of the 489 patients included in the analysis, 48 (9.8%) had hyperkalemia thought to be associated with ACEI-drug interactions. Univariate analysis using binary logistic regression revealed that advanced age (60 years or more), and taking more than 15 medications were independent risk factors significantly associated with hyperkalemia. However, current and previous smoking history appeared to be a protective factor. Risk factors identified as predictors of hyperkalemia secondary to ACEI-drug interactions by multi-logistic regression were: advanced age (adjusted OR 2.3, CI 1.07-5.01); renal disease (adjusted OR 4.7, CI 2.37-9.39); hepatic disease (adjusted OR 5.2, CI 1.08-25.03); taking 15-20 medications (adjusted OR 4.4, CI 2.08-9.19); and taking 21-26 medications (adjusted OR 9.0, CI 1.64-49.74).

CONCLUSION

Cardiac patients receiving ACEIs concomitantly with potentially interacting drugs are at high risk of experiencing hyperkalemia. Old age, renal disease, hepatic disease, and receiving large number of medications are factors that may significantly increase their vulnerability towards this adverse outcome; thus, frequent monitoring is advocated.

Potentially inappropriate prescribing to hospitalised patients

PURPOSE

The objective of this study was to evaluate the prevalence of potential drug-drug interactions (DDIs) in hospitalised patients in correlation with patient's age and number of drugs prescribed and to determine the prevalence of inappropriate drugs prescribed to elderly patients.

METHODS

Drugs prescribed during 1 day to all hospitalised patients at seven wards of Department of Medicine in University Hospital Rijeka were recorded by reviewing patient medical charts. Potential DDIs were evaluated using a list of potentially harmful drug combinations compiled from the literature. Beers criteria were used to identify potentially inappropriate medications in patients aged 65 years or older.

RESULTS

The study included 225 patients that received a total of 1301 drugs. Twenty-two percent of the patients receiving drug therapy were prescribed drug combinations that are potentially harmful. The most common potentially harmful drug combination was an ACE inhibitor with a potassium supplement (33.9% of all combinations). In the multivariate analysis, age and number of drugs are significantly associated with potential DDIs (r = 0.8629). One quarter of elderly patients received a drug potentially inappropriate considering their age. The most commonly prescribed potentially inappropriate drug was amiodarone, followed by diazepam.

CONCLUSION

Polypharmacy and older age have been proven to be important risk factors for potential drug interactions. We identified a high rate of prescribing potentially inappropriate medications among elders. Results of this study indicate that particular caution should be given when prescribing drugs to patients already receiving drugs and to elderly patients, considering the risk of drug-related problems.

Drug-drug interactions in a geriatric outpatient cohort: prevalence and relevance

BACKGROUND

The prevalence of drug-drug interactions (DDIs) in a geriatric population may be high because of polypharmacy. However, wide variance in the clinical relevance of these interactions has been shown.

OBJECTIVES

To explore whether adverse drug reactions (ADRs) as a result of DDIs can be identified by clinical evaluation, to describe the prevalence of ADRs and diminished drug effectiveness as a result of DDIs and to verify whether the top ten most frequent potential DDIs known to public pharmacies are of primary importance in geriatric outpatients in the Netherlands.

METHOD

All adverse events classified by the Naranjo algorithm as being a possible ADR and drug combinations resulting in diminished drug effectiveness were identified prospectively in 807 geriatric outpatients (mean age 81 years) at their first visit. The setting was a diagnostic day clinic. The Medication Appropriateness Index (MAI) and Beers criteria were used to evaluate drug use and identify possible DDIs. The ten most frequent potential interactions, according to a 1997 national database of public pharmacies ('Top Ten') in the Netherlands, and possible adverse events as a result of other interactions, were described. The effects of changes in medication regimen were recorded by checking the medical records.

RESULTS

In 300 patients (44.5% of the 674 patients taking more than one drug), 398 potential DDIs were identified. In 172 (25.5%) of patients taking more than one drug, drug combinations were identified that were responsible for at least one ADR or which possibly resulted in reduced effectiveness of therapy. Eighty-four of the 158 possible ADRs resulting from enhanced action of drugs forming combinations listed in the 'Top Ten' were seen in 73 patients. Only four DDIs resulting in less effective therapy that involved drug combinations in the 'Top Ten' were identified. Changes in drug regimens pertaining to possible interactions were proposed or put into effect in 111 of the 172 (65%) patients with possible DDIs. Sixty-one (55%) of these patients returned for follow-up. Of these, 49 (80%) were shown to have improved after changes were made to their medication regimen.

CONCLUSION

In this study, nearly half of the geriatric outpatients attending a diagnostic day clinic who were taking more than one drug were candidates for DDIs. One-quarter of these patients were found to have possible adverse events or diminished treatment effectiveness that may have been at least partly caused by these DDIs. These potential interactions can be identified through clinical evaluation. In the majority of patients (99 of 172) the potential interactions resulting in possible ADRs or diminished effectiveness were not present in the 'Top Ten' interactions described by a national database of public pharmacies, a finding that emphasizes that the particular characteristics of geriatric patients (e.g. frequent psychiatric co-morbidities) need to be considered when evaluating their drug use. At least 7% of all patients taking more than one drug, and 80% of those with possible drug interactions whose drug regimen was adjusted, benefited from changes made to their drug regimens.

Potential drug interactions in cancer patients receiving supportive care exclusively

Cancer patients at the end of life often take many medications and are at risk for drug interactions. The purpose of this study was to describe the epidemiology of potential drug interactions in cancer patients receiving supportive care exclusively. We retrospectively reviewed the charts of consecutive adult cancer outpatients attending palliative care clinics at the Princess Margaret Hospital, Toronto, Canada. Drugs were screened for interactions by the Drug Interaction Facts software, which classifies interactions by levels of severity (major, moderate, and minor) and scientific evidence (1-5, with 1=the strongest level of evidence). Among 372 eligible patients, 250 potential drug interactions were identified in 115 patients (31%, 95% confidence interval 26%-36%). The most common involved warfarin and phenytoin. Most interactions were classified as being of moderate severity (59%) and 42% of them were supported by Levels 1-3 of evidence. In multivariable analysis, increasing age (P<0.001), presence of comorbidity (P=0.001), cancer type (brain tumors, P<0.001), and increasing number of drugs (P<0.001) were associated with risk of drug interactions. Potential drug interactions are common in palliative care and mostly involve warfarin and anticonvulsants. Older patients, those with comorbid conditions, brain tumor patients, and those taking many medications are at greater risk of drug interactions.

Identification of drug interactions in hospitals--computerized screening vs. bedside recording

BACKGROUND AND OBJECTIVE

Managing drug interactions in hospitalized patients is important and challenging. The objective of the study was to compare two methods for identification of drug interactions (DDIs)--computerized screening and prospective bedside recording--with regard to capability of identifying DDIs.

METHODS

Patient characteristics were recorded for patients admitted to five hospitals. By bedside evaluation drug-related problems, including DDIs, were prospectively recorded by pharmacists and discussed in multidisciplinary teams. A computer screening programme was used to identify DDIs retrospectively--dividing DDIs into four classes: A, avoid; B, avoid/take precautions; C, take precautions; D, no action needed.

RESULTS

Among 827 patients, computer screening identified DDIs in 544 patients (66%); 351 had DDIs introduced in hospital. The 1513 computer-identified DDIs had the following distribution: type A 78; type B 915; type C 38; type D 482. By bedside evaluation, 99 DDIs were identified in 73 patients (9%). The proportions of computer recorded DDIs which were also identified at the bedside were: 5%, 8%, 8%, 2% DDIs of types A, B, C and D respectively. In 10 patients, DDIs not registered by computer screening were identified by bedside evaluation. The drugs most frequently involved in DDIs, identified by computerized screening were acetylsalicylic acid, warfarin, furosemide and digitoxin compared with warfarin, simvastatin, theophylline and carbamazepine, by bedside evaluation.

CONCLUSION

Despite an active prospective bedside search for DDIs, this approach identified less than one in 10 of the DDIs recorded by computer screening, including those regarded as hazardous. However, computer screening overestimates considerably when the objective is to identify clinically relevant DDIs.

Identification of severe potential drug-drug interactions using an Italian general-practitioner database

OBJECTIVE

To analyze prescriptions in a general-practitioner database over 1 year to determine the frequency, the characteristics, and the monitoring of the severe potential drug-drug interactions (DDIs).

METHODS

We retrospectively analyzed the clinical records from 16 general practitioners in the Veneto region, an area in northern Italy. The study covered the period from January 1 to December 31, 2004. We selected all severe and well-documented interactions according to the book Drug Interaction Facts by David S. Tatro (Facts and Comparisons, St. Louis, MO, 2006). We grouped severe potential DDIs according to their specific potential risk, and for the most frequently interacting drug pairs, we investigated whether some specific tests had been prescribed by physicians for safety monitoring.

RESULTS

During the study period, 16,037 patients (55% female) with at least one drug prescription were recorded, and a total of 185,704 prescriptions relating to 1,020 different drugs were analyzed. Ramipril was the most frequently prescribed drug followed by acetylsalicylic acid and atorvastatin. The final number of different types of severe potential DDIs was 119, which occurred 1,037 times in 758 patients (4.7% of the total number of patients). More than 80% of drugs involved in severe potential DDIs were cardiovascular drugs. Digoxin was the most frequently involved drug. Electrolyte disturbances, increase in serum digoxin levels, risk of hemorrhage, severe myopathy or rhabdomyolysis, and cardiac arrhythmias were the most commonly implicated potential risks. When considering patients using digoxin with loop or thiazide diuretics for more than 5 months, 72% had at least one test to monitor potential digoxin toxicity, whereas 28% had no tests. Sixty-four percent of patients using digoxin with amiodarone, verapamil, or propafenone had an ECG and/or digoxin monitoring, and 36% of them did not have any tests.

CONCLUSIONS

The present study revealed that, in a group of Italian general practitioners, the risks of severe potential drug interactions are relatively low and the drugs concerned are few. Analyses of specific tests showed that physicians are generally aware of the potential risks caused by digoxin drug associations. However not all patients were closely monitored and this should be improved.

Potential drug interactions and duplicate prescriptions among cancer patients

BACKGROUND

Cancer patients receive numerous medications, including antineoplastic agents, drugs for supportive care, and medications for comorbid illnesses. Therefore, they are at risk for drug interactions and duplicate prescribing.

METHODS

A questionnaire eliciting information on demographics and medications taken in the previous 4 weeks was given to adult outpatients receiving systemic anticancer therapy for solid tumors. The Drug Interaction Facts software, version 4.0, was used to identify potential drug interactions and to classify them by level of severity (major, moderate, or minor) and the strength of scientific evidence for them (using categories [1-5] of decreasing certainty). Summary statistics and logistic regression were used to analyze the data. All statistical tests were two-sided.

RESULTS

The survey was completed by 405 patients. We observed 276 potential drug interactions, and at least one potential interaction was identified in 109 patients (27%; 95% confidence interval [CI] = 23% to 31%). Of the potential interactions, 25 (9%) were classified as major and 211 (77%) as moderate. Nearly half (49%) of potential interactions were supported by level 1 or 2 scientific evidence. Most potential drug interactions (87%) involved non-anticancer agents such as warfarin, antihypertensive drugs, corticosteroids, and anticonvulsants, but some (n = 36, 13%) involved antineoplastic agents. In multivariable analysis, increased risk of receiving drug combinations in which there were potential drug interactions was associated with receipt of increasing numbers of drugs (odds ratio [OR] = 1.4 per additional drug, 95% CI = 1.26 to 1.58, P<.001 from the Wald chi-square test), type of medication (drugs to treat comorbid conditions versus supportive care medications only; OR = 8.6, 95% CI = 2.9 to 25, P<.001), and the presence of brain tumors. Thirty-two (8%) patients were exposed to duplicate medications, most often corticosteroids, proton pump inhibitors, or benzodiazepines.

CONCLUSION

Potential drug interactions were common among cancer patients and most often involved medications to treat comorbid conditions. Duplicate medications were infrequent.

Drug-associated disease: cytochrome P450 interactions

Critically ill patients generally are older, frequently have organ failure, and commonly receive multiple medications, all of which make them susceptible to adverse effects of drugs. Drug interactions are a common adverse effect, and many are predictable based on understanding the mechanisms that underlie drug interactions. This article identifies commonly used medications in critically ill patients and the associated drug interactions that may occur with emphasis on the cytochrome P450 enzyme system.