The difference between effectiveness and efficacy of antimalarial drugs in Kenya

OBJECTIVE To demonstrate the difference between effectiveness and efficacy of antimalarial (AM) drugs in Kenya. METHODS We undertook a series of linked surveys in four districts of Kenya between 2001 and 2002 on (i) community usage of nationally recommended first- and second-line AM drugs; (ii) commonly stocked AM products in the retail and wholesale sectors; and (iii) quality of the most commonly available first- and second-line AM products. These were combined with estimates of adherence and clinical efficacy to derive overall drug effectiveness. RESULTS The overall modelled effectiveness for sulphadoxine-pyrimethamine (SP) was estimated to be 62% compared with 85% for reported SP clinical efficacy. For amodiaquine the modelled effectiveness was 48% compared with 99% reported efficacy during the same time period. CONCLUSIONS The quality of AM products and patient adherence to dosage regimens are important determinants of drug effectiveness, and should be measured alongside clinical efficacy. Post-registration measures to regulate drug quality and improve patient adherence would contribute significantly to AM drug performance.