Response of Kampuchean strains of Plasmodium falciparum to antimalarials: in-vivo assessment of quinine and quinine plus tetracycline; multiple drug resistance in vitro.

Forty-three patients were enlisted in the in-vivo test for sensitivity of Kampuchean strains of Plasmodium falciparum to quinine. The mean parasite density count on day 0 was 32,398 asexual parasites per microliter of blood. With a dosage of 1.5 g quinine base daily for 10 days the average parasite clearance time was 5.6 days, and the average duration of fever 3.4 days. The in-vivo test was evaluated at 7 and 10 days after the start of therapy. After 7 days only 16 patients were parasite negative by microscopic examination (S); 20 patients had an RI recrudescence, four patients responded at the RII level and three at the RIII level. Evaluating the in-vivo test at 10 days, the number of patients parasite negative increased to 18, the number of those with an RI level of resistance increased to 21, two patients gave an RII response and two had an RIII level of resistance. Twenty-two adult males were included in an in-vivo test of the sensitivity of P. falciparum to quinine plus tetracycline. The course of treatment was: quinine 3 x 500 mg daily for 10 days, tetracycline 3 x 500 mg for 7 days. Parasite density counts on day 0 averaged 11,393 asexual parasites per microliter of blood. The average parasite clearance time was 5.9 days, and the average duration of fever was 3.8 days. After 7 days of treatment, 81.8% of patients were parasite negative, while one patient had a recrudescence after 17 days (RI). Three infections were resistant at the RII level. By prolongation of the observations to day 10, the parasitaemia was cleared in all patients, i.e. all infections were sensitive to quinine plus tetracycline. Thirty-four patients with falciparum malaria were screened for in-vitro resistance to chloroquine, mefloquine and quinine using the WHO standard micro-test.(ABSTRACT TRUNCATED AT 250 WORDS)