A method of monitoring drugs for adverse reactions I. α-methyldopa and haemolytic anaemia

Summary Existing methods of detecting adverse drug reactions are reviewed and an information system whereby the total number of patients exposed to a drug and the total number of patients developing an adverse reaction can be ascertained is described. Its potential as a monitoring system was tested by investigating, in 204 patients identified as receiving -methyldopa, the known association of haemolytic anaemia with that drug. — Patients remaining on -methyldopa were repeatedly screened and in this series one patient had developed haemolytic anaemia and 10 patients had antibodies to -methyldopa as evidenced by a positive direct antiglobulin test. Follow-up effectively determined the frequency of haemolytic anaemia which appeared to be a relatively small hazard and should not prejudice the use of the drug. This study has highlighted the difficulties in the adequate assessment of hypertension prior to commencing treatment and has shown that drug monitoring for adverse reactions may have an important role in the establishment of criteria for the more effective use of drugs.