Absolute contraindications in relation to potential drug interactions in outpatient prescriptions: analysis of the first five million prescriptions in 1999

Drug-Drug Interactions and the Risk of Emergency Hospitalizations: A Nationwide Population-Based Study

BACKGROUND

Several studies suggest a significant risk of hospitalization because of drug-drug interactions in the general population. However, to our knowledge, this risk has never been measured precisely in a large population.

OBJECTIVE

We aimed to estimate the risk of emergency hospitalization associated with exposure to the contraindicated concomitant use of interacting drugs in the general population.

METHODS

A self-controlled case-series analysis was carried out on a cohort of 150,000 subjects randomly selected from the French national health insurance database, between 01/01/2016 and 31/12/2016. Exposure to the contraindicated concomitant use of interacting drugs was defined as the overlapping period of dispensings of drugs contraindicated because of clinically meaningful drug-drug interactions. The main outcome, incidence rate ratios, comparing the incidence rate of emergency hospitalizations during each category of exposure time periods with that during the reference period, was estimated using the conditional Poisson regression model.

RESULTS

Over the study period, 967 subjects were exposed to at least one contraindicated concomitant use of interacting drug and 177 had been exposed and presented at least one emergency hospitalization. Compared to the unexposed follow-up time, the risk of emergency hospitalization increased during exposure to contraindicated concomitant use of interacting drug periods (incidence rate ratio: 2.41; 95% confidence interval 1.55-3.76). This could translate into 7200 (4500-8900) potentially preventable emergency hospitalizations yearly in France.

CONCLUSIONS

We evidenced an almost 2.5-fold increase in the risk of emergency hospitalizations during periods of exposure to contraindicated concomitant use of interacting drugs, with a potential public health impact exceeding 7000 preventable hospitalizations yearly in France. These results confirm the need to reinforce training in prescription practices and tools for prevention concerning contraindicated concomitant use of interacting drugs. These would especially concern drugs involved in an increase in long QT syndrome when associated such as citalopram, and highly prescribed drugs with a risk of overdose if co-prescribed with cytochrome P450 inhibitors, such as antigout and lipid-lowering drugs.

Prevalence of Potential Pharmacological Interactions in Patients Undergoing Systemic Chemotherapy in a Tertiary Hospital

Introduction: Pharmacological interactions are frequently observed in patients with chronic diseases, and their occurrence is proportional to the amount of medication used daily. Patients undergoing chemotherapy treatment commonly have comorbidities, which favor a greater prevalence of polypharmacy, increasing the risk of drug interactions. Therefore, the aim of this study was to estimate the prevalence of drug interactions in patients undergoing intravenous chemotherapy treated at a hospital oncology service in southern Brazil. Methods: This was an observational study with a cross-sectional design that was carried out with the analysis of secondary data obtained through the review of medical records. The population assessed consisted of all cancer patients who received intravenous chemotherapy from October to December 2020. Results: Out of the 297 patients included in the study, 231 (77.8%) had at least 1 potential pharmacological interaction. In total, 1044 drug interactions were found that were classified according to severity, resulting in 18 (1.7%) contraindicated drug-drug interactions (DDI), 699 (67%) severe, 281 (26.9%) moderate, and 46 (4.4%) minor interactions. There was an association between polypharmacy and the prevalence of drug interactions. Conclusion: The results demonstrate that a large percentage of patients undergoing chemotherapy are susceptible to drug interactions. Thus, it is necessary that prescribers consider all drugs used by patients and, when possible, prescribe alternative drugs that have less potential for interaction in order to prevent drug interactions adverse effects and provide a better prognosis for patients.

Pilot study: Evaluation of potential drug-drug interactions in hospitalized pediatric patients

PURPOSE

Evaluate the type and severity of potential drug-drug interactions and identify risk factors involved, in pediatric patients admitted in a hospital setting.

METHODS

Transversal retrospective analytical study was carried out with hospitalized pediatric patients from a Hospital in the West of Mexico, second and third level. The patients included were ≤18 years old hospitalized in the children wards; those admitted at the emergency room, neonatal intermediate and intensive therapy units were not included. Medical prescriptions were reviewed taking into consideration anthropometric characteristics, diagnosis and number of drugs prescribed to identify potential drug-drug interactions using Micromedex 2.0 database.

RESULTS

88 patients were included, an average of 4.6 ± 2.8 of drugs were prescribed per patient. 37 subjects (42%) presented some degree of potential drug-drug interactions of which 25.5% were major and 27.7% moderate according to the software. Identified risk factors were: age ≥ 4 years (OR 1.917; 95% CI 1.081-3.399), BSA ≥ 0.8m2(OR 1.825; 95% CI 1.021-3.263), height ≥ 1 m (OR 2.556;95% CI 1.322 - 4.941), and number of prescribed medications ≥ 4 (OR 2.106;95% CI 1.248 - 3.556).

CONCLUSION

Some of the interactions found were for the benefit of the patient, but others were considered undesirable because they altered the pharmacokinetics of some of the medications administered. Detecting in time the harmful interactions for a patient may favor the patient's safety.

Patient's lack of understanding producing insulin drug-interactions in Southeast Brazilian primary care clinics

Detrimental drug-drug interactions (DDIs) in Diabetic patients could be from the simultaneous use of multiple drugs, polypharmacy. Brazilian public health studies evaluating the practical knowledge about drug interactions are scarce. This study's objective is to identify drug interactions and prevalence of detrimental DDIs in diabetic patients attending Brazilian basic health system clinics.

METHODS

Patients using insulin between the age of 18-90 years were selected to complete the MedTake questionnaire, to evaluate the indication, dosage, regimen and drug interaction. The MedTake test was employed. For each medicine, the test was scored as the percentage of correct actions and compared with printed instructions one single researcher downloaded all the data was from the municipality's computerized system.

RESULTS

The median age of recruits was 60.2 ± 14.3 and MedTake test scores were low 60.3 ± 20. One hundred patients missed the correct dose question, 40 missed why they were prescribed the drug, indication and 65 missed the therapeutic regimen. These diabetes patients did not know the DDIs between insulin combined with other medicines. Drugs that had more interaction with insulin were: acetylsalicylic acid (40%), enalapril (18%), losartan (32%) and hydrochlorothiazide (23%).

CONCLUSIONS

Diabetes patients without practical knowledge about insulin interacting with other pharmaceutical drugs that can produce DDIs with other medicines illustrates a need to develop education programs for diabetics.

Reliability, ease of use and usefulness of I-MeDeSA for evaluating drug-drug interaction alerts in an Australian context

Background

Recently, attention has shifted to improving the design of computerized alerts via the incorporation of human factors design principles. The Instrument for Evaluating Human Factors Principles in Medication-Related Decision Support Alerts (I-MeDeSA) is a tool developed in the United States to guide improvements to alert design and facilitate selection of electronic systems with superior design. In this study, we aimed to determine the reliability, ease of use and usefulness of I-MeDeSA for assessing drug-drug interaction (DDI) alerts in an Australian context.

Methods

Using the I-MeDeSA, three reviewers independently evaluated DDI alert interfaces of seven electronic systems used in Australia. Inter-rater reliability was assessed and reviewers met to discuss difficulties in using I-MeDeSA and the tool’s usefulness.

Results

Inter-rater reliability was high (Krippendorff’s alpha = 0.76), however, ambiguous wording and the inclusion of conditional items impacted ease of use. A number of items were not relevant to Australian implementations and as a result, most systems achieved an I-MeDeSA score of less than 50%.

Conclusions

The I-MeDeSA proved to be reliable, but item wording and structure made application difficult. Future studies should investigate potential modifications to the I-MeDeSA to improve ease of use and increase applicability to a variety of system configurations.

Electronic supplementary material

The online version of this article (10.1186/s12911-018-0666-y) contains supplementary material, which is available to authorized users.

The Role of Technicians in Managing Computerized Drug–Drug Interaction Alerts in Community Pharmacies and the Relationship to Pharmacist Managers' Attitudes

Background:

Community pharmacies are where identification and prevention of drug–drug interactions (DDIs) typically occur. Technicians have been shown to play some role in the initial screening of DDIs in community pharmacies.

Objectives:

To examine the role of technicians in the management of DDI alerts in community pharmacies and the possible relationship to the attitudes of pharmacy managers toward DDI alerts.

Methods:

A national survey of pharmacist managers in 3,000 community pharmacies was conducted. Data collected included demographics, workload issues, handling of DDIs, and pharmacists' attitudes toward computerized DDI alerts.

Results:

Of questionnaires returned, 736 could be used. Technicians were more often allowed or sometimes allowed to override lower level DDI alerts without prior review by a pharmacist. However, some pharmacies (2.1%) allowed or sometimes allowed technicians to override interactions with the highest potential clinical significance. Stores with the highest use of technology were less likely to allow technicians to override insignificant interactions. Stores that allow technicians to override clinically significant interactions were less confident in their program's ability to provide meaningful alerts and more likely to agree that alerts are a waste of time and that the volume of alerts makes differentiating important from unimportant DDIs more difficult.

Conclusions:

Pharmacy technicians play a limited role in the management of DDI alerts, but could be used to help ensure that a patient's profile of medications is up-to-date and determine whether the patient had already been receiving the combination without notable problem.

Potential drug-drug interactions in pediatric outpatient prescriptions for newborns and infants

OBJECTIVES

To surveyed the quantities, types, and related information of potential drug-drug interactions (DDIs) and estimate the off-label use percentage of pediatric outpatient prescriptions for newborns and infants from the National Health Insurance Research Database (NHIRD) of Taiwan.

BACKGROUND

Adverse drug reactions (ADR) may cause morbidity and mortality, potential drug-drug interactions (DDI) increase the probability of ADR. Research on ADR and DDI in infants is of particular urgency and importance but the related profiles in these individuals are not well known.

METHODS

All prescriptions written by physicians in 2000 were analyzed to identify potential DDIs among drugs appearing on the same prescription sheet.

RESULTS

Of a total of 150.6 million prescription sheets, with 669.5 million prescriptions registered in the NHIRD of Taiwan, six million (3.99%) prescription sheets were for 2.1 million infants with 19.4 million (2.85%) prescriptions. There were 672,020 potential DDIs in this category, accounting for 3.53% per prescription; an estimated one DDI in every three patients. The interactions between aspirin and aluminum/magnesium hydroxide were most common (4.42%). Of the most significant drug-drug interactions, the interaction of digoxin with furosemide ranked first (20.14%), followed by the interactions of cisapride with furosemide and erythromycin (6.02% and 4.85%, respectively). The interactions of acetaminophen and anti-cholinergic agents comprised most types of drug-drug interactions (6.62%).

CONCLUSION

Although the prevalence rates of DDIs are low, life-threatening interactions may develop. Physicians must be reminded of the potential DDIs when prescribing medications for newborns and infants.

Physicians' responses to computerized drug-drug interaction alerts for outpatients

INTRODUCTION

Adverse drug reactions (ADR) increase morbidity and mortality; potential drug-drug interactions (DDI) increase the probability of ADR. Studies have proven that computerized drug-interaction alert systems (DIAS) might reduce medication errors and potential adverse events. However, the relatively high override rates obscure the benefits of alert systems, which result in barriers for availability. It is important to understand the frequency at which physicians override DIAS and the reasons for overriding reminders.

METHOD

All the DDI records of outpatient prescriptions from a tertiary university hospital from 2005 and 2006 detections by the DIAS are included in the study. The DIAS is a JAVA language software that was integrated into the computerized physician order entry system. The alert window is displayed when DDIs occur during order entries, and physicians choose the appropriate action according to the DDI alerts. There are seven response choices are obligated in representing overriding and acceptance: (1) necessary order and override; (2) expected DDI and override; (3) expected DDI with modified dosage and override; (4) no DDI and override; (5) too busy to respond and override; (6) unaware of the DDI and accept; and (7) unexpected DDI and accept. The responses were collected for analysis.

RESULTS

A total of 11,084 DDI alerts of 1,243,464 outpatient prescriptions were present, 0.89% of all computerized prescriptions. The overall rate for accepting was 8.5%, but most of the alerts were overridden (91.5%). Physicians of family medicine and gynecology-obstetrics were more willing to accept the alerts with acceptance rates of 20.8% and 20.0% respectively (p<0.001). Information regarding the recognition of DDIs indicated that 82.0% of the DDIs were aware by physicians, 15.9% of DDIs were unaware by physicians, and 2.1% of alerts were ignored. The percentage of total alerts declined from 1.12% to 0.79% during 24 months' study period, and total overridden alerts also declined (from 1.04% to 0.73%).

CONCLUSION

We explored the physicians' behavior by analyzing responses to the DDI alerts. Although the override rate is still high, the reasons why physicians may override DDI alerts were well analyzed and most DDI were recognized by physicians. Nonetheless, the trend of total overrides is in decline, which indicates a learning curve effect from exposure to DIAS. By analyzing the computerized responses provided by physicians, efforts should be made to improve the efficiency of the DIAS, and pharmacists, as well as patient safety staffs, can catch physicians' appropriate reasons for overriding DDI alerts, improving patient safety.

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.

Quality of interaction database management systems

Objective

To identify drug interaction databases (DID) and assess the quality of their structures.

Method

A search was made of the literature for DID and a series of exclusion and structural quality criteria were defined (at least 4 quality criteria: classification according to severity, classification according to level of evidence, bibliographical reference data, description of clinical management, and 11 criteria used for weighting). The level of compliance of every DID with the criteria defined was analysed, together with the level of compliance of each criteria in each DID.

Results

A total of 54 DID were identified, 30 of which complied with exclusion criteria and 15 of which did not meet the minimum criteria. The rest of the criteria were evaluated in 9 DID: Botplus and Medinteract (100%), SEFH Guide, Lexi-interact and Medscape (89%), Hansten (83%), Micromedex and Stockley (78%), Drug Interactions Facts (68%). Ninety-two percent of the DID describe the mechanism of action, 87% classify the information according to the active ingredient, 75% do not state they have any conflict of interest, classify according to level of severity, have electronic format, and are easy to search. A total of 67% are specific DID, 62% are classified according to level of evidence, contain bibliographical references, and describe clinical management.

Conclusions

A third of the DID comply with the minimum criteria. Differences were observed in the level and compliance criteria among Spanish and foreign DID. Some of the main DID used as references in the bibliography have significant structural defects: no web presentation, no multi-check function and others.

A composite screening tool for medication reviews of outpatients: general issues with specific examples

Regular performance of medication reviews is prominent among methods that have been advocated to reduce the extent and seriousness of drug-related problems, such as adverse drug reactions, drug-disease interactions, drug-drug interactions, drug ineffectiveness and cost ineffectiveness. Several screening tools have been developed to guide practising healthcare professionals and researchers in reviewing the medication patterns of elderly patients; however, each of these tools has its own limitations. This review discusses a wide range of general prescription-, treatment- and patient-related issues that should be taken into account when reviewing medication patterns by implicit screening. These include generic and therapeutic substitution; potentially superfluous or inappropriate medications; potentially inappropriate dosages or duration of treatment; drug-disease and drug-drug interactions; under-treatment; making use of laboratory test results; patient adherence, experiences and habits; appropriate dosage forms and packaging. A broad selection of specific examples and references that can be used as a basis for explicit screening of medication patterns in outpatients is also offered.

Clinical relevance of drug-drug interactions : a structured assessment procedure

INTRODUCTION

Computerised drug interaction surveillance systems (CIS) may be helpful in detecting clinically significant drug interactions. Experience with CIS reveals that they often yield alerts with questionable clinical significance, fail to provide relevant information on risk factors for the adverse reaction of the interaction and fail to detect all significant drug interactions. These problems highlight the importance of transparency and selectivity in choosing the drug interactions to be included in CIS. In The Netherlands, the Working Group on Pharmacotherapy and Drug Information is responsible for maintenance of the CIS of the Royal Dutch Association for the Advancement of Pharmacy (KNMP).

METHODS

The Working Group developed an evidence-based procedure for structured assessment of drug-drug interactions and revised all drug interactions in the CIS accordingly.

RESULTS

For every drug interaction four core parameters were assessed: (i) evidence on the interaction; (ii) clinical relevance of the potential adverse reaction resulting from the interaction; (iii) risk factors identifying patient, medication or disease characteristics for which the interaction is of special importance; and (iv) the incidence of the adverse reaction. On the basis of this assessment the drug-drug interactions for inclusion in the CIS were selected. After revision of the drug combinations in the KNMP-CIS, the Working Group judged 22% of the combinations to be not interacting and another 12% to be interacting but not requiring action. On the basis of this assessment the subset of drug combinations for which interaction alerts are generated and the information on management of a drug interaction alert for users of the CIS were adapted. When an alert is generated by the CIS, the user of the system is supplied with comprehensive information on the four core parameters, the mechanism of the interaction and critical information for management of the interaction for the individual patient.

DISCUSSION

This structured procedure offers the possibility for transparent and reproducible assessment of the clinical relevance of drug interactions.

CONCLUSION

A CIS selectively generating interaction alerts based on this assessment may help in realising the goal of good clinical practice and may offer a methodology to further increase drug safety.

Clinical risk management in Dutch community pharmacies: the case of drug-drug interactions

BACKGROUND

The prevention of drug-drug interactions requires a systematic approach for which the concept of clinical risk management can be used. The objective of our study was to measure the frequency, nature and management of drug-drug interaction alerts as these occur in daily practice of Dutch community pharmacies.

METHODS

In total, 63 Dutch pharmacies collected all drug-drug interaction alerts during 153 research days (on average 2.4 days/pharmacy), as well as variables related to these alerts, such as involved medicines, first time or recurrent drug-drug interaction, same or different prescribers, patient data (age, sex) and information about the management of drug-drug interactions by the pharmacy. The latter was discriminated into internal procedures only and external action, such as communication with the patient, the prescriber or the anticoagulation clinic and prescription modification. All drug-drug interactions were classified into categories of clinical relevance (A-F) and available evidence (0-4).

RESULTS

A total of 43,129 prescription-only medicines were dispensed during the study period. On average, 16.8 interaction alerts per day per pharmacy were collected. Approximately 6% of all prescriptions generated a drug-drug interaction alert. Of all alerts (n = 2572), 31.1% occurred for the first time and with 21% two different prescribers were involved. The 20 most frequently occurring drug-drug interaction alerts accounted for approximately 76% of all alerts. Cardiovascular drugs, NSAIDs, oral contraceptives and antibacterials were most frequently involved. External action was taken in response to 27.3% of the alerts, meaning either a modification of one of the concerned prescriptions (n = 65; 9.3%), communication with the prescriber or anticoagulation clinic (n = 90; 12.8%) or communication with the patient or a relative (n = 547; 77.9%). Where there was no external action (n = 1860; 72.3%), pharmacists concluded in about two-thirds of cases that the drug-drug interaction had been managed in the past. Other reasons not to intervene externally were for instance: incorrect alert; acceptable drug-drug interaction; or outcome of the interaction considered irrelevant. Adjusted for several variables, a first alert was found to be a main determinant for external action. After stratifying for first alerts no other significant determinants were found.

CONCLUSIONS

A high frequency of drug-drug interaction alerts was found. Most concerned recurrent alerts, which were the main reason not to act externally. Concerning the assessment phase in the risk-management process, drug-drug interactions with no or low evidence/relevance should be reconsidered. Concerning the management of drug-drug interactions in pharmacies, the opportunity to actively suppress alerts for a certain period of time should be studied in more detail. There are indicators that the management of patient-orientated advice could be improved and a greater degree of consistency developed for the management of first and recurrent interaction alerts.

Co-dispensing of contraindicated medications in patients using cisapride in Italy

PURPOSE

To investigate the co-dispensing of contraindicated medications in patients using cisapride in an Italian population.

METHODS

The study included patients who had at least one cisapride prescription dispensed between 1 April 1997 and 30 September 2000. The proportion of cisapride users with concomitant medications, the proportion of prescriptions of cisapride with an overlapping dispensing of a contraindicated medication and the proportion of person-days of cisapride use concomitant with contraindicated medications, were calculated.

RESULTS

In the 4-year study period, 249,740 total cisapride prescriptions, which corresponded to 382,835 packages, were dispensed to 91,204 users (52,442 female, 57.5%). Concomitant use of contraindicated drugs was identified in 4403 cisapride users (4.83%). Throughout the study period, there was an increase in the proportion of cisapride users with contraindicated co-prescriptions: 4.29% in 1997, 4.99% in 1998, 5.15% in 1999, but a decline to 3.34% in 2000. In each year, this figure was higher in males, with the highest proportion reported in 1999 (5.50%). A total of 7215 cisapride prescriptions (2.85%) were concomitant with contraindicated drugs, ranging from 2.27% in September 1998 to 3.55% in January 1999. Cisapride prescriptions were most frequently associated with macrolide antibiotics (1.14%) and class III antiarrhythmics (1.03%).

CONCLUSIONS

In the period 1997-2000, a substantial proportion of cisapride prescriptions were concomitant with contraindicated medications. In Italy in 1998, the National Health Authority issued a bulletin warning about the risk of serious arrhythmias after concomitant use of contraindicated drugs. Despite this warning, there was no reduction in contraindicated drug uses.

Evaluation of a Drug-Drug Interaction Alert Structure through the Retrospective Analysis of Statins-Macrolides Co-Prescriptions

The aim of this work was the evaluation of the existent drug interaction alert structure in Spain, which is based on yellow cards notifications and circulation of drug alert letters, through the retrospective analysis of CYP3A-metabolized statins and macrolides co-prescriptions in the Spanish province of Badajoz between May and September 2001. The period of study was planned to include the release of 2 drug alert letters released by the Spanish Drug Agency in June and July, addressed to all healthcare professionals, which warned against the concomitant prescription of statins and inhibitors of their metabolism, e.g. macrolides antibacterials. 4,600,764 prescriptions were examined, 664 of which corresponded to combinations of statins and macrolides. Although a decrease was detected in the number of these co-prescriptions throughout the study, 80 of these corresponding to 67 patients were still being prescribed in September, after the warnings by the Spanish Drug Agency had been released. 431 physicians prescribed these drugs simultaneously, with 22.9% of them having more than one patient at potential risk. Doctors working at rural healthcare centres or not directly attached to any healthcare facility were more prone to prescribe unsafe coprescriptions than those working at urban health centre. This study shows that the present drug alert system is not fully efficient when facing a situation like the one retrospectively reviewed in this study, in which a prompt action, in this case termination of potentially hazardous coprescriptions, was required. New systems developed to improve prescribing, including a new method based on personal contact between Drug Surveillance Centres and general practitioners, are discussed.

Using a computerized drug prescription screening system to trace drug interactions in an outpatient setting

BACKGROUND

Drug-drug interactions are one of the main causes of adverse effects. These events have been studied most often in hospital settings; however, investigations on prescribing based on community practice have shown a high prevalence rate of potential drug interactions.

OBJECTIVE

To develop a computerized system able to trace drug interactions quickly through the identification of clinicians issuing potentially unsafe prescriptions.

METHODS

We retrospectively evaluated hazardous concomitant prescriptions of hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) and azole antifungals, which were invoiced through 9 months of 2001 within an outpatient setting. The study was conducted in Badajoz, a southern Spanish province, and was divided in three 3-month periods according to the release of 2 warning notes on this drug combination by the Spanish Drug Agency. Prescriptions written during this period were optically scanned each month, and the resulting information, including data from patients, physicians, and drugs involved, was converted to a database and searched for potentially unsafe coprescriptions.

RESULTS

A total of 8342711 prescriptions were invoiced in the period of study, 174 of which were for a statin-azole combination. The number of these prescriptions remained fairly constant during periods I and II (63 and 71, respectively), decreasing to 40 in period III. Some clinicians (12.6%) repeatedly prescribed a hazardous drug combination at some point in this study, whereas 18 of 171 patients who received the hazardous coprescription at any time did so repeatedly within a given period. The impact of drug alerts was remarkably deeper in urban rather than rural care centers.

CONCLUSIONS

The computerized drug prescription handling system described here is able to readily identify physicians and patients who issue/consume hazardous drug combinations, thus allowing both the possibility of individually informing the healthcare professionals involved and early detection of adverse effects.