Pamaquin Resistance in a Strain of Plasmodium gallinaceum and its relationship to Other antimalarial Drugs

1. A four- to eight-fold increase in resistance to pamaquin has been developed in a strain of Plasmodium gallinaceum in chicks. 2. Pamaquin resistance conferred no resistance to proguanil, sulphadiazine, mepacrine, chloroquine or sontochin, but it conferred some resistance to pentaquine and to quinine. 3. An appreciable loss in resistance to pamaquin was observed in the pamaquin-resistant strain after it had been maintained in the absence of the drug, in a patent state of infection, for a period of 6 months. 4. No synergism was observed between pamaquin and quinine when these drugs were tested, in combined doses, upon active infections of P. gallinaceum.