Signalling drug-induced rash with 36 drugs recently marketed in the United Kingdom and studied by Prescription-Event Monitoring.

This study examines skin rash, as a reported event, in the patients who used one of the 36 drugs recently released to the UK market and studied by Prescription-Event Monitoring between 1985 and 1992. The results are also compared to the voluntary reports on rash as a possible adverse drug reaction sent to the Committee on Safety of Medicines (CSM). Specific types of skin rash (e.g. exfoliative dermatitis) are excluded. The rate of rash has been calculated for 2 periods, the first month (T1) and the subsequent 5 months (T2) after the first prescription for the drug. Despite the heterogeneity of the patient groups, the rate for rash between the 2nd and 6th months was consistent in the 36 drugs and probably represented the baseline rate of rash due to a variety of nonspecific causes. This rate (T2) was around 1 per 1,000 patients per month (ranging from 0.5 to 2 per 1,000 patients per month). On the other hand, in the first month after the first prescription for the drug, the rate (T1) varied substantially from 0.9 to 6.4 per 1,000 patients per month. Diltiazem had the highest first monthly rate. These rates are listed for the 36 drugs. The difference of the rates was tested by 2 methods: a standard statistical test assuming a Poisson model and a method based on the ratio of the rates for the 2 periods. When the 2 rates (T1 and T2) were similar to each other, drug induced rash was considered to be rare.(ABSTRACT TRUNCATED AT 250 WORDS)