Antihypertensive drug prescribing in Grampian

To assess the cost implications of changing prescribing patterns for antihypertensive drugs and to analyse adherence to guidelines and formulary in Grampian region over a 1 year period.

Data on all prescriptions for antihypertensive medicines between November 2001 and October 2002 were obtained from Grampian Health Board. The total quantity and cost of each drug prescribed was calculated and compared with November 1998 to October 1999. Adherence to the local formulary and 1999 British Hypertension Society guidelines for first line agents and prescribing of generic drug names were analyzed for each practice.

There was an increase in the total number of prescriptions for antihypertensive drugs from 504929 in 1998/99 to 741620 in 2001/02, and a corresponding increase in total cost from pound 4.52 million to pound 6.79 million. Increases were seen in all drug classes, particularly angiotensin II antagonists (246.27%). Adherence to the local formulary was good, with an average of 91.25% (SD 5.94%) of prescribing consistent with recommended agents. This fell to 71.70% (SD 23.10%) for angiotensin II antagonists. Prescription using generic name was related to whether the practice dispensed medication or not: the mean level of generic prescribing in dispensing practices was 75.25% and in nondispensing practices was 89.02% (mean difference 13.76 (9.27, 18.26), P < 0.001).

There was a substantial increase in prescribing volume and cost of antihypertensives between 1998/99 and 2001/02. This trend is likely to have continued, given changing targets and indications for therapy. Although practices generally showed high concordance with formulary recommendations, newer agents such as angiotensin II antagonists were less consistent, possibly related to pharmaceutical influences on prescribing. Dispensing practices were more likely to prescribe branded drugs which may reflect current reimbursement policies. Changing prescribing practices by encouraging formulary based prescribing and prescribing of generic agents may help offset the cost implications of guideline driven increases in antihypertensive drug prescribing. Education, and reviewing payment practices in dispensing and smaller practices, may also have a role.