A pharmacoepidemiologic study of drug interactions in a Brazilian teaching hospital

The effect of different intensivist staffing patterns on the rate of potential drug-drug interactions in adult trauma intensive care units

BACKGROUND

Drug-drug interactions (DDIs) have created alarming challenges for public health, especially in those admitted to intensive care units (ICUs). Many studies have shown that involvement of intensivists in the ICUs improves the outcome and decreases the treatment costs. The effect of academic versus non-academic (therapeutic) intensivist as well as hours of coverage and attendance of intensivist on potential DDIs (pDDIs) was evaluated in six adult trauma ICUs of a level one trauma center.

METHODS

In this 6-month cross-sectional study, 200 patients were included. The DDIs were classified into five groups, including type A, B, C, D, and X. pDDIs were defined as interactions belonged to C, D and X categories. Patients in six adult ICUs with three different patterns of intensivist staffing models including type A (once-daily therapeutic intensivist visit followed by 24 h on-call), B (twice-daily academic intensivist visit, 8 h of attendance in ICU and 16 h on-call) and C (all criteria just like ICU type B, except for the presence of therapeutic instead of academic intensivist) were screened for pDDIs.

RESULTS

In total, 3735 drug orders and 3869 drugs (193 different types) were screened and 1826 pDDIs were identified. Type C, D and X interactions accounted for 60.6%, 35.5%, and 3.9% of all pDDIs, respectively. The mean of pDDI per patient was significantly higher (p-value < 0.001) in the ICU type A than ICU types C and B. The frequency of pDDIs was the highest in the type A ICUs. A statistically significant relationship was observed between the number of prescribed drugs and ICU length of stay (p-value < 0.001 and p = 0.009, respectively).

CONCLUSION

Different patterns of intensivist staffing affect pDDIs to varying degrees. In the studied ICUs academic versus therapeutic intensivist, twice versus once-daily visit, and 8 h attendance with16 h on-call versus 24 h on-call were associated with more reductions in pDDIs.

PLAIN LANGUAGE SUMMARY

The impact of different intensivist staffing patterns in ICUs on the rate of potential drug-drug interactionsDrug-drug interactions (DDIs) have created alarming challenges for public health, especially in patients admitted to intensive care units (ICUs). Many studies have shown that involvement of intensivists in the ICUs improves the outcome and limits the costs. Considering the high incidence of potential DDIs (pDDIs) occurring for critically ill patients and the importance of ADRs caused by pDDIs in ICUs, the effect of the presence of an academic versus therapeutic intensivist, as well as the hour of coverage of intensivist on prevalence of pDDIs was evaluated in six adult trauma ICUs of a level one trauma center in Shiraz, Iran. We also determined the prevalence of pDDIs and their associated risk factors. To the best of our knowledge, this is the first study that has assessed the effect of various ICU physician staffing models on the incidence and pattern of pDDIs.

Potential Psychotropic Drug Interactions among Drug-dependent People

Using psychiatric drugs to treat drug dependence and its comorbidities is very common. The objective of this study was to analyze the interactions between prescribed drugs for patients treated at a specialized mental health-care center for persons who use drugs, located in the state of Santa Catarina, Brazil. A cross-sectional study was conducted on secondary data collected from 2010 to 2018. We reviewed the medical records of patients aged 18 years or older who took psychotropic drugs and had any type of substance dependence. The analysis of psychotropic drug interactions was conducted in three databases: Medscape, Drug Interactions Checker, and Micromedex. We included 1,022 of the 2,322 patients attending the care center during the study period. Psychotropic drug interactions were found in 779 (76.4%) study participants, and they presented 2,292 (100%) interactions, out of which 136 (6.0%) had minor clinical risk, 537 (23.4%) had moderate risk, and 1,619 (70.6%) had major risk for the patient, totaling 172 incompatible combinations between two psychotropic drugs. Of the total number of interactions, 128 were pharmacokinetic and 44 were pharmacodynamic. The high number of psychotropic drug interactions is a serious public health issue. Psychopharmacological treatment should be carefully addressed to be safe for the patient.

Prevalence and significance of potential drug-drug interactions among cancer patients receiving chemotherapy

Background

Cancer patients often receive multiple drugs to maximize their therapeutic benefit, treat co-morbidities and counter the adverse effects of chemotherapy. Concomitant administration of multiple drugs increases the risk of drug interactions leading to compromised therapeutic efficacy or safety of therapy. The purpose of this study was to identify the prevalence, levels and predictors of potential drug-drug interactions (pDDIs) among cancer patients.

Methods

Six hundred and 78 patients receiving chemotherapy from two tertiary care hospitals were included in this cross-sectional study. Patient medication profiles were screened for pDDIs using the Micromedex® database. Logistic regression analysis was performed to identify the predictors of pDDIs.

Results

The overall prevalence of pDDIs was 78%, majority of patients had 1–2 pDDIs (39.2%). A total of 1843 pDDIs were detected. Major-pDDIs were most frequent (67.3%) whereas, a significant association of pDDIs was found between > 7 all prescribed drugs (p < 0.001) and ≥ 3 anti-cancer drugs (p < 0.001). Potential adverse outcomes of these interactions include reduced therapeutic effectiveness, QT interval prolongation, tendon rupture, bone marrow suppression and neurotoxicity.

Conclusions

Major finding of this study is the high prevalence of pDDIs signifying the need of strict patient monitoring for pDDIs among cancer patients. Patients at higher risk to pDDIs include those prescribed with > 7 any types of drugs or ≥ 3 anticancer drugs. Moreover, list of most frequently identified major and moderate interactions will aid health care professional in timely identification and prevention of pDDIs.

Potential Drug-Drug Interactions with Antimicrobials in Hospitalized Patients: A Multicenter Point-Prevalence Study

Background

Improper use of antimicrobials can cause adverse drug events and high costs. The purpose of this study was to investigate the frequency and potential drug–drug interactions associated with antimicrobials among hospitalized patients.

Material/Methods

This study was conducted on the same day in 5 different hospitals in Turkey. We included patients aged ≥18 years who received at least 1 antimicrobial drug and at least 1 of any other drug. The Micromedex^® online drug reference system was used to control and describe the interactions. Drug interactions were classified as contraindicated, major, moderate, and minor.

Results

Potential drug–drug interactions with antimicrobials were 26.4% of all interactions. Five (42%) of 12 contraindicated interactions and 61 (38%) of 159 major interactions were with antimicrobials. Quinolones, triazoles, metronidazole, linezolid, and clarithromycin accounted for 173 (25.7%) of 673 prescribed antimicrobials, but were responsible for 141 (92.1%) of 153 interactions. In multivariate analysis, number of prescribed antimicrobials (odds ratio: 2.3001, 95% CI: 1.6237–3.2582), number of prescribed drugs (odds ratio: 1.2008, 95% CI: 1.0943–1.3177), and hospitalization in the university hospital (odds ratio: 1.7798, 95% CI: 1.0035–3.1564) were independent risk factors for developing drug interactions.

Conclusions

Due to risk of drug interactions, physicians should be more cautious when prescribing antimicrobials, particularly when prescribing quinolones, linezolid, azoles, metronidazole, and macrolides.

Prevalence of drug-drug interactions in geriatric patients at an ambulatory care pharmacy in a tertiary care teaching hospital

Objective

A cross-sectional study was performed from February to May 2015, to estimate the prevalence of drug–drug interactions in geriatric patients at the ambulatory care pharmacy at King Abdul-Aziz Medical City in Jeddah, Saudi Arabia.

Results

A total of 310 patients were included, with a mean age (± SD) of 73.78 ± 6.96, and 48.70% were female. The overall prevalence of DDIs of all categories was 90.64%. Category B DDIs was 55.80%, category C DDIs 87.74%, category D DDIs 51.93%, and category X DDIs 16.45%. Atorvastatine plus omeprazole was identified as the most common interacting pair, with a prevalence of 25.26%. Multivariate logistic regression analysis showed that category D or X DDIs are more likely to occur in the female patient (OR = 1.79; 95% CI 1.07, 2.97), the patient taking more than three medications (OR = 22.62; 95% CI 2.93, 174.83), and the patient with more than two conditions (OR = 3.09; 95% CI 1.81, 5.27).

Potential drug-drug interactions and their risk factors in pediatric patients admitted to the emergency department of a tertiary care hospital in Mexico

Background

Drug-drug interactions (DDIs) detected in a patient may not be clinically apparent (potential DDIs), and when they occur, they produce adverse drug reactions (ADRs), toxicity or loss of treatment efficacy. In pediatrics, there are only few publications assessing potential DDIs and their risk factors. There are no studies in children admitted to emergency departments (ED). The present study estimates the prevalence and describes the characteristics of potential DDIs in patients admitted to an ED from a tertiary care hospital in Mexico; in addition, potential DDI-associated risk factors are investigated.

Methods

A secondary analysis of data from 915 patients admitted to the ED of the Hospital Infantil de México “Federico Gómez” was conducted. The Medscape Drug Interaction Checker software was used to identify potential DDIs. The results are expressed as number of cases (%), means (95% CI) and medians (25-75^th percentiles). Count data regressions for number of total and severity-stratified potential DDIs were performed adjusting for patient characteristics, number of administered drugs, days of stay, presence of ADRs and diagnoses.

Results

The prevalence of potential DDIs was 61%, with a median of 4 (2–8). A proportion of 0.2% of potential DDIs was “Contraindicated”, 7.5% were classified as “Serious”, 62.8% as “Significant” and 29.5% as “Minor”. Female gender, age, days of stay, number of administered drugs and diagnoses of Neoplasms (C00-D48), Congenital malformations (Q00-Q99), Diseases of the Blood, Blood-forming Organs and Immunity (D50-D89) and Diseases of the nervous system (G00-G99) were significantly associated with potential DDIs.

Conclusion

The prevalence of potential DDIs in the ED is high, and strategies should therefore be established to monitor patients’ safety during their stay, in addition to conducting investigations to estimate the real harm potential DDIs inflict on patients.

Potential drug-drug interactions in pediatric patients admitted to intensive care unit of Khyber Teaching Hospital, Peshawar, Pakistan: A cross-sectional study

PURPOSE

To investigate frequencies, levels, clinical relevance and predictors of potential drug-drug interactions (pDDIs) in pediatric intensive care unit (PICU).

METHODS

Case notes of 411 patients were reviewed for pDDIs through Micromedex. Frequencies, levels and clinical relevance of pDDIs were reported. Logistic regression was applied to calculate the odds-ratios for predictors of pDDIs.

RESULTS

We recorded pDDIs in 59.4% patients. Major-pDDIs were found in 34.5% patients. Total 990 pDDIs were identified, of which, 37.8% were of moderate-severity and 30.6% of major-severity. Patient's case notes of top-ten pDDIs showed presence of signs/symptoms such as fever, jaundice, vomiting, anorexia, tachycardia, drowsiness, & lethargy; and abnormalities in labs such as total leukocytes count, blood urea nitrogen, alanine aminotransferase, & potassium-level. Odds of exposure to major-pDDIs were significantly higher in patients aged 6-12years (p=0.008); hospital stay of ≥7days (p=0.05); and ≥11 prescribed medicines (p<0.001).

CONCLUSION

Substantial numbers of patients in PICU are exposed to pDDIs. Major-pDDIs are of particular concern. Timely identification of pDDIs, preferably with computerized source, is crucial point for their management. Monitoring of clinically relevant parameters and identification of various predictors are needed to minimize or prevent the associated negative consequences of pDDIs.

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.

[Antidepressants: use, adherence and awareness among medical students]

This study assessed the degree of adherence and drug-related awareness and opinions regarding the importance of guidance with respect to treatment among medical students who use antidepressants. It is a cross-sectional descriptive study, carried out in a public Medical School in the state of Sao Paulo, Brazil. Of the 289 students interviewed, 33 (11.4%) use or had already used antidepressants, with fluoxetine being the most prescribed. The nurse was not cited as being responsible for guidance on the antidepressant. Although most students had received guidance on antidepressants, they did not heed guidance and still had doubts regarding their use. There was a statistically significant association regarding the consumption of other drugs in addition to antidepressants and the existence of side effects, as well as regarding an increase of the dosage without medical consultation and the existence of such side effects. Actions are necessary to acknowledge the importance of the teaching of psychopharmacology in the training of the medical professional and for greater harmony between theory and practice.

Assessment of potential drug-drug interactions and its associated factors in the hospitalized cardiac patients

Drug-drug interactions (DDIs) may result in the alteration of therapeutic response. Sometimes they may increase the untoward effects of many drugs. Hospitalized cardiac patients need more attention regarding drug-drug interactions due to complexity of their disease and therapeutic regimen. This research was performed to find out types, prevalence and association between various predictors of potential drug-drug interactions (pDDIs) in the Department of Cardiology and to report common interactions. This study was performed in the hospitalized cardiac patients at Ayub Teaching Hospital, Abbottabad, Pakistan. Patient charts of 2342 patients were assessed for pDDIs using Micromedex® Drug Information. Logistic regression was applied to find predictors of pDDIs. The main outcome measure in the study was the association of the potential drug-drug interactions with various factors such as age, gender, polypharmacy, and hospital stay of the patients. We identified 53 interacting-combinations that were present in total 5109 pDDIs with median number of 02 pDDIs per patient. Overall, 91.6% patients had at least one pDDI; 86.3% were having at least one major pDDI, and 84.5% patients had at least one moderate pDDI. Among 5109 identified pDDIs, most were of moderate (55%) or major severity (45%); established (24.2%), theoretical (18.8%) or probable (57%) type of scientific evidence. Top 10 common pDDIs included 3 major and 7 moderate interactions. Results obtained by multivariate logistic regression revealed a significant association of the occurrence of pDDIs in patient with age of 60 years or more (p < 0.001), hospital stay of 7 days or longer (p < 0.001) and taking 7 or more drugs (p < 0.001). We found a high prevalence for pDDIs in the Department of Cardiology, most of which were of moderate severity. Older patients, patients with longer hospital stay and with elevated number of prescribed drugs were at higher risk of pDDIs.

Evaluation of Potential Drug-Drug Interactions with Antidepressants in Two Tertiary Care Hospitals

BACKGROUND

Limited resources of healthcare system and high use of antidepressants have raised some serious concerns regarding proper surveillance system of prescribed medicines. Not much literature is available from Pakistan regarding the potential drug-drug interactions (pDDIs) associated with antidepressants.

OBJECTIVE

The objective of this study was to assess the frequency of pDDIs associated with antidepressants, their severity, significance and their association with patient characteristics.

MATERIALS AND METHODS

A prospective, observational study was conducted in two major hospitals of Karachi for the period of three months. Patient profiles, medication charts, and physician notes were thoroughly reviewed to gather all the relevant information. Inclusion and exclusion criteria were set prior to data collection. The collected data was then analysed using Micromedex Drug-REAX System. Descriptive and binomial logistic regression analysis was used to express results.

RESULTS

Of 245 prescriptions reviewed, 141 prescriptions had at least one pDDI (57.5%). A total of 181 pDDIs were identified in prescription containing antidepressant. The ratio of pDDI per prescriptions was 0.78. 42.5% interactions were moderate in severity, 30% of interactions were rapid in onset, and 43% were considered as significant interactions. Polypharmacy (OR=3.41, p< 0.001) and presence of chronic problems (OR=2.14, p=0.002) were significantly associated with the occurrence of pDDIs. Citalopram and diclofenac (11.6%) was commonly prescribed interacting pair in this study.

CONCLUSION

The findings of this study recorded high frequency of antidepressants associated pDDIs. Our results confirm the significant association of polypharmacy with the occurrence of pDDIs with antidepressants. Future studies are warranted to establish these results by including hospitals in different parts of the country.

Drug-drug interaction software in clinical practice: a systematic review

PURPOSE

Several electronic databases which report the prevalence of drug-drug interactions (DDIs) are used as a tool for evaluation of potentially harmful DDIs. The aim of our review was to evaluate the usability and appropriateness of commercially available electronic databases which assess the prevalence of potential DDIs.

METHODS

The systematic electronic literature search was conducted with the following search terms: "database" AND "software," and "drug-drug interactions" AND "database," and the inclusion and exclusion criteria were applied in order to identify the publications of interest.

RESULTS

A total of 3766 papers were identified by systematic search. After applying inclusion and exclusion criteria, 38 publications were included in the analysis. The most commonly used software in the included studies was Micromedex® Drug-Reax, for which some authors argue to be the most reliable due to highest sensitivity. It gives information about clinical consequences of DDIs, classifies underlying mechanism and onset of the adverse outcome (either rapid, or delayed) as well as severity (such as minor, moderate, or major), and provides the level of evidence which supports this information. This data is also provided by Drug Interaction Facts®, Lexi-Interact®, and Pharmavista®. A small number of studies which compared assessment of DDIs with electronic database and the clinician's assessment showed large discrepancy in number and relevance of detected DDIs. The overlap was in some cases as low as 11 %.

CONCLUSION

The deficiency of clinical relevance of detected DDIs should be addressed in the upcoming research as it would provide more relevant information to the prescribers' in clinical practice.

Beers criteria-based assessment of medication use in hospitalized elderly patients in southern Brazil

BACKGROUND

Population aging has evolved gradually. Polypharmacy to control disease associated with age-related physiological changes increases the risk of adverse drug reactions, including drug interactions among the elderly population.

OBJECTIVE

This study was intended to assess the medications used by the elderly population, aiming at identifying the potentially inappropriate medications according to the Beers Criteria.

MATERIALS AND METHODS

We conducted a cross-sectional study on medical records to assess the use of medications by elderly patients admitted to the Hospital Nossa Senhora da Conceição in 2011. The variables included gender, age, reasons for admission, comorbidities, and medications used by the elderly patients.

RESULTS

In total, we reviewed 440 medical records. Patients were predominantly male (51.6%). The total number of medications used was 5904, with an average of 13.4 per person. The three most commonly used drugs were dipyrone, omeprazole, and metoclopramide. The most frequently used drugs according to the Anatomical Therapeutic Chemical Classification (ATC) system were those of the alimentary tract and metabolism, nervous system, and cardiovascular system. Of the 255 types of drugs used, 42 (16.4%) were included in the Beers list, and the three most often used were metoclopramide, ketoprofen, and aspirin.

CONCLUSION

The number of medications used per patient was substantial, and potentially inappropriate medications according to the Beers Criteria were significant as well.

Profile of drug interactions in hospitalized children

Introduction

The expected therapeutic response may be affected by the presence of drug interactions. With the high number of reports on new drug interactions, it has been difficult for health professionals to keep constantly updated. For this reason, computer systems have helped identify such interactions.

Objectives

To verify the rate and profile of drug interactions in medical prescriptions to hospitalized pediatric patients.

Methods

A descriptive study investigated prescriptions to hospitalized pediatric patients. The study included patients between 0 and 12 years old, containing 4 or more drugs in their prescriptions. The analysis of interaction and incompatibility possibilities in prescribed drugs used Micromedex / Drug-Reax® program.

Results

From 2005 to 2006, 3,170 patients were investigated, and 11,181 prescriptions were analyzed, a mean value of 3.5 prescriptions/patient. In total, 6,857 drug interactions were found, which corresponds to 1.9 interaction/prescription. Among them, relevance to ampicillin and gentamicin, found in 220 (3.2%) prescriptions. In total, 2,411 drug incompatibilities in via y were found, a mean value of 0.5/prescription, with emphasis on vancomycin and cefepime, found in 243 (10.0%) prescriptions.

Conclusion

The presence of drug interactions is a permanent risk in hospitals. This way, the utilization of computer programs, pharmacotherapy monitoring of patients and the pharmacist presence in the multidisciplinary team are some manners of contributing to hospitalized patients’ treatment.

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.

Prevalence of potential drug interactions in an Iranian general hospital

The hazards of prescribing many drugs, including side-effects, drug-drug interactions and difficulties of compliance have long been recognized as particular problems when prescribing. This study estimates the rate and factors associated with potential drug-drug interactions in prescriptions from wards of An Iranian General Hospital. Data were retrieved from the pharmacy of a general hospital (200 beds) during one year period 2010. Potential drug-drug interaction were identified using a computerized drug-drug interaction database system (Prescription Analyzer 2000, Sara Rayane Co., Iran). Patients of both genders and 15 years-old or more were included in this study. Prescriptions with two or more drugs prescribed were selected during one year period 2010. Gender number of drugs and therapeutic drug classes on prescriptions were explored as associated factors to drug-drug interaction. The overall prevalence of potential drug-drug interaction was 20.3%. The risks of severe potential drug interactions were relatively high and the rate of potential drug-drug interaction was significantly higher in women (60.6%) and the patients aged over 60 years old (57.1%). The frequency of the potentially severe drug-drug interaction was 10.8% with digoxin-furosemide as the most common interacting pair (5.91%). A positive correlation was found between drug-drug interaction, patient's age, number of drugs and drugs acting on cardiovascular system. So cardiology women inpatients, age more then 60 years old, and patients prescribed digoxin and angiotensin-converting enzyme inhibitors should be closely monitored for adverse outcomes from drug-drug interaction.

Potential drug-drug interactions in prescriptions to patients over 45 years of age in primary care, southern Brazil

BACKGROUND

Few cross-sectional studies involving adults and elderly patients with major DDIs have been conducted in the primary care setting. The study aimed to investigate the prevalence of potential drug-drug interactions (DDIs) in patients treated in primary care.

METHODOLOGY/PRINCIPAL FINDINGS

A cross-sectional study involving patients aged 45 years or older was conducted at 25 Basic Health Units in the city of Maringá (southern Brazil) from May to December 2010. The data were collected from prescriptions at the pharmacy of the health unit at the time of the delivery of medication to the patient. After delivery, the researcher checked the electronic medical records of the patient. A total of 827 patients were investigated (mean age: 64.1; mean number of medications: 4.4). DDIs were identified in the Micromedex® database. The prevalence of potential DDIs and major DDIs was 63.0% and 12.1%, respectively. In both the univariate and multivariate analyses, the number of drugs prescribed was significantly associated with potential DDIs, with an increasing risk from three to five drugs (OR = 4.74; 95% CI: 2.90-7.73) to six or more drugs (OR = 23.03; 95% CI: 10.42-50.91). Forty drugs accounted for 122 pairs of major DDIs, the most frequent of which involved simvastatin (23.8%), captopril/enalapril (16.4%) and fluoxetine (16.4%).

CONCLUSIONS/SIGNIFICANCE

This is the first large-scale study on primary care carried out in Latin America. Based on the findings, the estimated prevalence of potential DDIs was high, whereas clinically significant DDIs occurred in a smaller proportion. Exposing patients to a greater number of prescription drugs, especially three or more, proved to be a significant predictor of DDIs. Prescribers should be more aware of potential DDIs. Future studies should assess potential DDIs in primary care over a longer period of time.

Prevalence of potential drug-drug interactions in bone marrow transplant patients

OBJECTIVE

To assess the prevalence of potential drug-drug interactions (DDIs) in bone marrow transplantation (BMT) patients at the time of pre-infusion (day -1), to describe the potential DDIs and assess their frequency and severity.

SETTING

The study was developed in a tertiary care hospital in São Paulo, Brazil.

METHOD

Cross-sectional study based on examining the medical prescriptions from the pre-infusion day (day -1) of 70 BMT patients. Potential DDIs were analyzed using Drug-Reax(®) and categorized according to levels of severity, evidence, and onset (rapid and delayed). Only interactions of major or moderate severity were included in the potential DDI analysis.

MAIN OUTCOME MEASURE

Prevalence of potential DDIs in patients during the preinfusion phase of BMT.

RESULTS

Data were analysed for 70 BMT patients. The median age was 36.5 years; 52.9% (37) of the patients were male, and 65.7% (46) were undergoing autologous BMT. The patients received a median of 8 drugs each. Up to 128 potential DDIs were detected, 60.0% (42) of patients had at least 1 potential DDI and 21.4% (15) were exposed to at least 1 major potential DDI. The most commonly involved drugs were cyclosporine (9, 28.1%), phenytoin (8, 25%) and fluconazole (5, 15.6%). Most potential DDIs had moderate severity (110, 85.9%), a pharmacokinetic mechanism (67, 52.3%), and were classified as delayed onset (106, 82.8%). For major interactions, fluconazole + sulfamethoxazole/trimethoprim, diazepam + fentanyl, fluconazole + levofloxacin and fentanyl + fluconazole were the most frequent.

CONCLUSIONS

The prevalence of potential DDIs during the conditioning period of BMT was high as a consequence of the therapeutic complexity of the procedure. Most potential DDIs identified in the study may result in clinically relevant consequences as they could lead to nephrotoxicity, cardiotoxicity, and other undesirable adverse effects. Careful monitoring of clinical and laboratory parameters is essential to ensure a successful BMT and to avoid adverse drug events related to DDI.

Economic impact of potential CYP450 pharmacokinetic drug-drug interactions among chronic low back pain patients taking opioids

Chronic low back pain (cLBP) patients who take at least 1 CYP450-metabolized opioid analgesic agent concurrent with at least 1 other CYP450-metabolized medication experience a drug-drug exposure (DDE), which puts them at risk for a pharmacokinetic drug-drug interaction (PK DDI). This study compared utilization of healthcare resources and associated payments in cLBP patients with and without incident DDEs with the potential to cause PK DDIs. A retrospective database analysis examined the associated clinical events, healthcare utilization (measured in terms of claims for office visits, outpatient visits, emergency department visits, and hospitalization), and cost to the health plan, as defined as the sum of health plan payments for resources used. Patients were grouped into 2 cohorts by age (those under 65 and those 65 years and over). In the 6 months after exposure, total healthcare payments were significantly higher for DDE patients than those without DDEs (no-DDE), in both in the younger ($7,086, SD = $8,370) and $6,353, SD = $8,352, respectively, P < 0.001) and the older cohorts ($7,806 vs. $7,043, respectively, P = 0.013). Younger and older patients with DDE had significantly higher prescription payments than those without DDE ($2,041, SD = $2,706 vs. $1,565, SD = $2,349, respectively, P < 0.001 for younger and $2,482, SD = $2,481 vs. $2,286, SD = $2,521, respectively, P = 0.044 for older patients). Both older and younger patients with DDE had significantly more claims for office visits and higher associated payments than similar patients without DDE. Patients in the study who experienced DDEs that placed them at risk for PK DDIs had significantly greater utilization rates of healthcare resources and higher associated payments in the 6-month observation period following exposure.

Warfarin drug interactions: a comparative evaluation of the lists provided by five information sources

PURPOSE

Detecting potential drug interactions can lead to early interventions that protect patients from serious drug-related problems. The aim of this study was to evaluate the agreement among the lists of warfarin interactions provided by five information sources.

METHODS

The lists of warfarin interactions and the corresponding severity ratings and documentation levels presented by the three compendia and by the World Health Organization (WHO) Model Formulary were all compared, and each list was compared to that provided on the package insert of Marevan, a brand of warfarin. The compendia used were: Drug Interaction Facts, Drug Interactions: Analysis and Management and DRUG-REAX. A kappa coefficient was used to calculate the agreement among the sources.

RESULTS

A total of 537 interactions were listed. Only 13 (2.4%) were common to the five sources. The global Fleiss' kappa coefficient was -0.0080, which indicated poor agreement. Eleven warfarin interactions appeared only in the Marevan package insert. Importantly, 243 interactions (45.3% of the total) were deemed significant in at least one compendium. Only two warfarin interactions were reported as critical by all three compendia and by WHO. The most critical interactions cited by the compendia were missing from the package insert.

CONCLUSIONS

Poor agreement was found among five sources listing warfarin interactions. Potentially severe clinical consequences might occur due to these discrepant recommendations. Finally, the lack of standard terminology and clinical guidance, as well as the possible inaccuracy of severity ratings and documentation might contribute to heterogeneous procedures in clinical practice.

Interação medicamentosa: conhecimento de enfermeiros das unidades de terapia intensiva

OBJETIVO: Avaliar o conhecimento das interações medicamentosas (IM)de enfermeiros que atuam em unidades de terapia intensiva de adultos, de três hospitais públicos de Goiás. MÉTODOS: Estudo descritivo, transversal. População 64 e amostra, 51 enfermeiros. Construiu-se um instrumento de coleta de dados, utilizando informações da base de dados MICROMEDEX®. RESULTADOS: Sobre o conhecimento de IM e manejo clínico, houve uma relação de acertos e erros de, aproximadamente, 50% dos enfermeiros. As duplas de medicamentos que os enfermeiros mais acertaram foram relativas a medicamentos com ação sedativa e analgésica e as que apresentaram mais erros, foram as de ação anti-infecciosa e anti-hipertensiva. CONCLUSÃO: É necessário sensibilizar autoridades e profissionais sobre a importância das IM na UTI e implementar ações para a segurança dos pacientes na terapêutica medicamentosa.

Prevalence of potential drug interactions in patients in an intensive care unit of a university hospital in Brazil

OBJECTIVES

To investigate the prevalence of potential drug interactions at the intensive care unit of a university hospital in Brazil and to analyze their clinical significance.

METHODS

This cross-sectional retrospective study included 299 patients who had been hospitalized in the intensive care unit of the hospital. The drugs administered during the first 24 hours of hospitalization, in the 50th length-ofstay percentile and at the time of discharge were analyzed to identify potential drug-drug and drug-enteral nutrition interactions using DRUG-REAXH software. The drugs were classified according to the anatomical therapeutic chemical classification.

RESULTS

The median number of medications per patient was smaller at the time of discharge than in the 50th length-of-stay percentile and in the first 24 hours of hospitalization. There was a 70% prevalence of potential drug interactions at the intensive care unit at the studied time points of hospitalization. Most of the drug interactions were either severe or moderate, and the scientific evidence for the interactions was, in general, either good or excellent. Pharmacodynamic interactions presented a subtle predominance in relation to pharmacokinetic interactions. The occurrence of potential drug interactions was associated with the number of medications administered and the length of stay. Medications that induced cytochrome P450, drugs that prolong the QT interval and cardiovascular drugs were pharmacotherapy factors associated with potential drug interactions.

CONCLUSION

The study showed that potential drug interactions were prevalent in the intensive care unit due to the complexity of the pharmacotherapies administered. The interactions were associated with the number of drugs, the length of stay and the characteristics of the administered medications.

Economic impact of potential drug-drug interactions in opioid analgesics

OBJECTIVE

Patients managing chronic non-cancer pain with cytochrome P450 (CYP450)-metabolized opioid analgesics who concurrently take another CYP450-metabolized medication experience a drug-drug exposure (DDE), which puts them at risk for a pharmacokinetic drug-drug interaction (PK DDI). This study examined the economic impact of incident DDEs with the potential to cause PK DDIs compared to similar patients without such exposure.

STUDY DESIGN

This retrospective analysis used paid claims from a large, commercially insured population during January 1, 2004 through December 31, 2008.

METHODS

Propensity matching was used to control for baseline differences in comparisons between 85,043 exposed and 85,043 non-exposed patients.

RESULTS

Comparisons yielded mean total costs 6 months after the DDEs that were significantly higher in subjects with DDE versus matched subjects without DDE [$8165 (SD $11,357) vs. $7498 (SD $11,668), respectively, p<0.01] resulting in a difference of $667. This was driven by medical costs [$5520 (SD $10,505) vs. $5222 (SD $10,689), respectively, p<0.01] a $298 difference, and total prescription costs [$2646 (SD $3262) vs. $2276 (SD $3907), respectively, p<0.01] a $369 difference.

LIMITATIONS

The study design demonstrates associations only and cannot establish causal relationships. Further, relevant DDEs were not included if concurrent consumption occurred outside the index period and when CYP450 substances were consumed that are not reflected in pharmacy claims (herbals, over-the-counter medications).

CONCLUSION

Since concurrent exposure to DDEs with the potential to cause PK DDIs may be relatively common, policy decisions-makers should consider the use of long-acting opioids that are not metabolized through the CYP450 pathway.

Potential drug-drug interactions in prescriptions dispensed in community pharmacies in Greece

OBJECTIVES

To evaluate the nature, type and prevalence of potential drug-drug interactions (DDIs) in prescriptions dispensed in community pharmacies in Thessaloniki, Greece. Secondary objectives included the classification of DDIs as per pharmacotherapeutic class of the medications and the investigation of the relationship between medical specialties and the frequency of potential DDIs, as well as the relationship between DDIs and prescription size. Setting DDIs are a common cause of adverse drug reactions (ADRs) among patients using multiple drug therapy. In Greece a reliable computerized surveillance system for monitoring potential DDIs is not yet fully established. As a result, the prevalence of such DDIs in prescriptions dispensed by community pharmacies in Greece is unknown.

METHODS

We conducted a prospective, descriptive study. Over a 3-month period (November 2007-January 2008), a total of 1,553 handwritten prescriptions were collected from three community pharmacies in Thessaloniki, Greece. The prescriptions were processed using the Drug Interactions Checker within the www.drugs.com database. The identified potential DDIs were categorized into two classes, major and moderate, according to their level of clinical significance.

MAIN OUTCOME MEASURES

Overall 213 prescriptions had one or more potential DDIs and a total of 287 major and moderate DDIs were identified. Potential DDIs were identified in 18.5% of all prescriptions. Major DDIs were identified in 1.9% of all prescriptions and represented 10.5% of all DDIs detected, whereas moderate DDIs were identified in 16.6% of all prescriptions and represented 89.5% of all DDIs detected. The rate of DDIs increased with prescription size. The most common drug involved in major DDIs was amiodarone which interacts with potassium-wasting diuretics, digoxin, simvastatin and acenocoumarol.

CONCLUSIONS

Our results indicate that patients in Greece are at risk of ADRs caused by medications due to potential DDIs. An appropriate surveillance system for monitoring such interactions should be implemented and physicians should be more aware of potentially harmful DDIs. Pharmacists can contribute to the detection and prevention of drug-related injuries, especially of clinically meaningful DDIs that pose a potential risk to patient safety.

Frequency of potential interactions between drugs in medical prescriptions in a city in southern Brazil

CONTEXT AND OBJECTIVE

Drug interactions form part of current clinical practice and they affect between 3 and 5% of polypharmacy patients. The aim of this study was to identify the frequency of potential drug-drug interactions in prescriptions for adult and elderly patients. TYPE OF STUDY AND SETTING: Cross-sectional pharmacoepidemiological survey in the Parque Verde housing project, municipality of Cascavel, Paraná, Brazil, between December 2006 and February 2007.

METHODS

Stratified cluster sampling, proportional to the total number of homes in the housing project, was used. The sample consisted of 95 homes and 96 male or female patients aged 19 or over, with medical prescriptions for at least two pharmaceutical drugs. Interactions were identified using DrugDigest, Medscape and Micromedex softwares.

RESULTS

Most of the patients were female (69.8%), married (59.4%) and in the age group of 60 years or over (56.3%), with an income less than or equal to three minimum monthly salaries (81.3%) and less than eight years of schooling (69.8%); 90.6% of the patients were living with another person. The total number of pharmaceutical drugs was 406 (average of 4.2 medications per patient). The drugs most prescribed were antihypertensives (47.5%). The frequency of drug interactions was 66.6%. Among the 154 potential drug interactions, 4.6% were classified as major, 65.6% as moderate and 20.1% as minor.

CONCLUSION

The high frequency of drug prescriptions with a potential for differentiated interactions indicates a situation that has so far been little explored, albeit a reality in household surveys.

Use of drugs that act on the cytochrome P450 system in the elderly

OBJECTIVES

The objective of this study was to analyze medications that act on the cytochrome P450 (CYP450) enzymatic system and are used daily by non-institutionalized elderly individuals.

METHODS

A cross-sectional population-based study of elderly individuals (> or = 60 years old) was conducted. All continuously used medications with hepatic metabolism via CYP450 that are classified as substrates, inducers or inhibitors were considered. For the analysis, elderly individuals were stratified according to age groups, and hepatic metabolism activity due to daily alcohol consumption and smoking were considered.

RESULTS

Elderly individuals (396 in total: 222 women and 174 men) between 60 and 95 years of age (mean: 72.1) were assessed. Use of drugs that act on CYP450 was identified in 61.6% of the subjects. Drug use was observed among 16.2% of the subjects: three drugs among 9.8% and four or more among 6.3% of the subjects. The metabolic activities of the drugs used were classified as substrates (58.8%), inhibitors (14.9%), and inducers (4.3%). The main drugs used were beta-blockers and statins (as substrates), proton pump inhibitors and fluoxetine (as inhibitors), and prednisone and carbamazepine (as inducers).

CONCLUSIONS

The results demonstrate that the elderly use high levels of medications that act on CYP450, thereby increasing the risk of drug interactions in a group that is already vulnerable to adverse drug effects.