Acute falciparum infections treated in the Tampin district of the Feeeration of Malaya with a single dose of 100-300 mg of proguanil do not respond as they did two years ago. There were no failures in 1947: now about one infection in every four fails to respond.
Until May, 1949, no falciparum infection treated by us had resisted full therapeutic doses of proguanil: seven infections observed between May and July, 1949, resisted proguanil doses as great as, or greater than, the standard therapeutic course. The daily parasitaemia in five of these infections is recoreed.
Proguanil has been used widely but probably sporadically for the past two years throughout the Tampin district, whence the patients were drawn.
The implications of these observations are briefly discussed.