Serious Adverse Drug Reactions to Pyrimethamine-Sulphadoxine, Pyrimethamine-Dapsone and to Amodiaquine in Britain

Abstract

All reports of adverse reactions with pyrimethamine-sulphadoxine (Fansidar), pyrimethamine-dapsone (Maloprim), and amodiaquine spontaneously reported through the UK national post-marketing system were reviewed. Retrospective reporting rates of serious reactions associated with these drugs were analysed using prescription data from the Department of Health, derived from the Prescription Pricing Authority, and relevant pharmaceutical companies. Whilst interpretation of these data requires caution, they allowed comparison with reporting rates from other studies. The reported rate for all serious reactions to pyrimethamine-sulphadoxine was 1 : 2100 prescriptions, and for cutaneous reactions was 1 : 4900 prescriptions, with a fatality rate of 1 : 11 100. The reported rate for serious reactions to pyrimethamine-dapsone was 1 : 9100 prescriptions, and for blood dyscrasias was 1 : 20 000 prescriptions, with a fatality rate of 1 : 75 000. The reported rate of blood dyscrasias associated with amodiaquine was 1 : 2100 users with a fatality rate of 1 : 31 000. Serious hepatic disorders occurred in 1 : 11 1000 pyrimethamine-sulphadoxine prescriptions, 1 : 75 200 pyrimethamine-dapsone prescriptions, and in 1 : 15 650 amodiaquine users. 35% of cases received these drugs needlessly as they were not exposed to drug resistant strains of Plasmodium falciparum. Since few serious reactions have been reported to chloroquine plus proguanil, these data support guidelines which restrict the use of reviewed drugs for those at greatest risk of infection. Dosage data indicated that fatalities had taken higher doses and continued prophylaxis after onset of symptoms. Two thirds of serious reactions to the compound antimalarials were reported in females.