Drug utilization and morbidity statistics for the evaluation of drug safety in Sweden

For a continuous monitoring and evaluation of drug safety problems in Sweden, the Department of Drugs of the National Board of Health and Welfare has access to a number of computerised patient-, drug-, and disease-oriented registers. The usefulness and limitations of these registers are presented by examples. A recent increase in asthma deaths is presently being analysed by comparing information from death certificates and case records with drug sales and prescription data. A recent analysis of the cancer register showed no increased risk of malignant thyroid tumors after diagnostic or therapeutic doses of I 131. Similarly no increased risk of malformations after occupational exposure to hexachlorophene could be detected by analysing the malformation and medical birth-record registers in relation to hospital hexachlorophene use. The register of patient discharge diagnoses has been repeatedly used to analyse the incidence and pattern of drug induced blood dyscrasias and thromboembolism associated with oral contraceptives (OC). These analyses have resulted i.a. in the withdrawal of dipyrone and tenalidine and a decrease of the estrogen-content of OCs. At the same time about 1/3 of these serious adverse drug reactions (ADR) was found to have been reported to the ADR-register. By combining sales and prescription data with ADR-reports the risk of inducing lactic acidosis was found to be significantly higher for phenformin than for metformin. Also the incidence of tardive dyskinesia from longterm use of metoclopramide was found to be much higher than hitherto recognized. By use of these registers it is possible to obtain valuable information about the safety of drugs. The raw data must, however, be interpreted with care and often be supplemented with in depth studies of the various problems.