Background
The Beeston Primary Care Research Group was formed earlier this year to investigate preventable drug-related problems in Primary Care. The group is funded by NHS R&D support funding and uses a network of local Community Pharmacists and General Practitioners for the collection of data. Our first project investigated the incidence of prescribing potentially hazardous/contraindicated drug combinations.

Methods
A list of potentially hazardous/contraindicated drug combinations was compiled according to the latest reference books. Each drug or drug group in an interacting pair was included if likely to be prescribed at least one item per 10,000 patients per year in Nottingham general practices.

Using the above list, computerized medication records were searched for a period of one year (1 June 1999 � 31 May 2000) in five surgeries that cover 39900 patients in Nottingham. Overall 212 drug-drug interactions involving 126 drugs and 8 drug-disease interactions were screened for. The search results were investigated in detail by examining patients' notes. This included screening for adequate documentation and appropriate monitoring of the patients if such drug combinations were prescribed.

Results
Excluding non-current combinations, 44 patients were prescribed potentially dangerous drug-drug combinations and 30 patients had potentially dangerous drug-disease combinations. This represents an incidence rate of 1.10 and 0.75 per 1000 patient per year respectively. The potentially dangerous drug-drug combination that occurred most frequently was amiodarone with thyroid hormones. Several non-selective beta-blockers were prescribed for patients taking bronchodilators. Timolol and propranolol were involved in the majority of cases. A review of the medical notes demonstrated potential for reducing the occurrence of hazardous drug-drug combinations and improving patient safety.

Conclusion
The incidence of prescribing potentially dangerous drug-drug combinations appears to be relatively low in this study. However, the use of certain drugs such as amiodarone, terfenadine, nitrates and beta-blockers still involves a high risk of interacting with other medications or disease conditions and requires an increased awareness.