Incidence and possible causes of prescribing potentially hazardous/contraindicated drug combinations in general practice.

BACKGROUND: Preventing the use of medications where there is the potential for serious drug-drug interactions or drug-disease interactions (contraindications) is essential to ensure patient safety. Previous studies have looked at the incidence of prescribing contraindicated drug combinations, but little is known about the underlying reasons for the co-prescribing events. The objectives of this study were to estimate the incidence of prescribing contraindicated drug combinations in general practice and to explore the clinical context, possible causes and potential systems failures leading to their occurrence. METHODS: A list of contraindicated drug combinations was compiled according to established references. A search of computerised patient medication records was performed, followed by detailed chart review and assessment. The patient records from four general practices in an area of England were searched for a period of 1 year (1 June 1999-31 May 2000) to identify contraindicated drug combinations. All patients registered with the four participating practices during the study period were included (estimated n = 37 940). Medical records of the cases identified by the computer search were reviewed in detail and relevant information was extracted. Each case was then independently assessed by a pharmacist and a physician who judged whether the co-prescribing was justified and whether it was associated with an adverse drug event. Proximal causes and potential systems failures were suggested for each co-prescribing event. MAIN OUTCOME MEASURES AND RESULTS: Fourteen patients with potential drug-drug interactions and 50 patients with potential drug-disease interactions were identified. Overall, these represent an incidence of 1.9 per 1000 patient-years (95% CI 1.5, 2.3) or 4.3 per 1000 patients being concurrently prescribed > or =2 drugs per year (95% CI 3.2, 5.4). 62 cases involving 63 co-prescribing events were reviewed. Two-thirds of these events involved medications that were initiated by hospital doctors. Awareness of the potential drug-drug or drug-disease interactions was documented in one-third of the events at the time of initial co-prescribing. Within the study period, the co-prescribing was judged to be not justified in 44 events (70%). Potential drug-drug interactions possibly resulted in two adverse drug events. The majority of contraindicated co-prescribing related to drug-disease interactions involved the use of propranolol or timolol eye drops for patients receiving bronchodilators and the use of amiodarone for patients receiving levothyroxine sodium. CONCLUSION: The prescribing of contraindicated drug combinations was relatively rare in this study. Multiple possible causes and systems failures were identified and could be used to develop strategies for the prevention of prescribing errors involving contraindicated drug combinations in primary care.

Prescribing errors and other problems reported by community pharmacists.

INTRODUCTION: Prevention of medication errors is a priority for health services worldwide. Pharmacists routinely screen prescriptions for potential problems, including prescribing errors. This study describes prescribing problems reported by community pharmacists and discusses them from an error prevention perspective. METHOD: For one month, nine community pharmacists documented prescribing problems, interventions made, and the proximal causes of the problems. The results were presented to local GPs and pharmacists at a meeting and feedback was invited. RESULTS: For 32 403 items dispensed, pharmacists reported 196 prescribing problems (0.6%). The reporting rates ranged from 0.2%-1.9% between pharmacists and were inversely correlated to dispensing volume. Prescriptions containing incomplete or incorrect information accounted for two-thirds of the problems. Lack of information on the prescriptions and transcribing/typing errors were the most frequently cited proximal causes. A few pitfalls of computerized prescribing were observed. CONCLUSION: Although rates of prescribing problems reported were relatively low, community pharmacists and patients remain important safeguards. This study identified potential causes of prescribing errors, and illustrated areas which could be improved in the design of computerized prescribing systems, and the communication and sharing of information between GPs and pharmacists.