Antimalarial activity of demeclocycline against Plasmodium cynomolgi bastianellii in rhesus monkeys

Abstract

Demeclocycline was tested for causal prophylactic (at 25, 50 and 100 mg kg⁻¹ dose levels), radical curative (at 25, 50, 100 and 200 mg kg⁻¹ dose levels) and blood schizontocidal (at 25, 50 and 100 mg⁻¹ dose levels) activities against Plasmodium cynomolgi B in rhesus monkeys. For causal prophylactic activity, demeclocycline extended the prepatent period at all dose levels. The maximum delay in patency was observed at 100 mg kg-¹ (prepatent period = 40·66± 14·57 days). For radical curative activity, relapse was also delayed at all dose levels tested, and the relapse interval was found to be 47·0±18±24 days at 200 mg kg⁻¹. For blood schizontocidal activity, parasitaemia was initially cleared at all dose levels, followed by recrudescence in all monkeys. The recrudescence interval was found to be 17·0±5·2 days at 25 mg kg⁻¹ and 31·0±2·7 days at 50 mg kg⁻¹ However, three monkeys treated with 100 mg kg⁻¹ did not show parasites in thin blood smears during the observation period, but parasites were present in thick blood smears of all the monkeys after the end of the observation period. On the other hand, all monkeys treated with 1 mg kg⁻¹ of primaquine for causal prophylactic and radical curative activities and with 5 mg kg⁻¹ chloroquine for blood schizontocidal activity were cured.