Pyrimethamine Halofantrine

Antimalarial therapy employs the same agents and is based on the same principles. The blood-schizonticidal halofantrine is reserved for therapy only. The pyrimethamine-sulfadoxine combination may be used for initial selftreatment. 

Knowledge of local resistance patterns is important to determine the treatment regimen. There is increasing chloroquine and pyrimethamine-sulfado-xine (Fansidar) resistance in Africa and in some areas at the border of Thailand there is resistance for almost all antimalarial drugs including halofantrine, mefloquine and quinine. In these areas only the artemisinin derivatives (artemether, arteether, arte-sunate, dihydroartemisinin) are effective. 

Chloroquine, quinine, mefloquine, halofantrine, proguanil, pyrimethamine, and tetracyclines blood schizontocides) kill these asexual forms. Drugs which act on this stage in the cycle of the parasite may be used for ... 

Instances of mefloquine resistance were reported in Tanzania in 1983, in Thailand in 1989, and in Africa (Malawi) in 1991. Resistance to combinations of mefloquine with sulfadoxine and pyrimethamine was reported in 1985 (SEDA-13, 808) (40 4). The possibility of crossresistance between mefloquine and halofantrine was raised in 1990 (SEDA-13, 808) (45). Currently there are extensive areas, including Thailand, Cambodia, Laos, Papua New Guinea, and Myanmar, where P. falciparum... 

Drugs used to treat an acute attack. Blood schizonticides are used to suppress an acute attack, and the various drugs used include oral chloroquine, mefloquine or quinine plus pyrimethamine or doxycycline or halofantrine. 

Pyrimethamine-sulfadoxine or, plus Tetracycline or, plus Clindamycin Mefloquine Halofantrine... 

Other Artemether, Artemotil, Artesunate, Atovaquone, Halofantrine, Lumefantrine, Proguanil, Pyrimethamine, SuKadoxine... 

Pyrimethamine/sulfadoxine and tetracycline have been shown to increase halofantrine levels, and may therefore increase its toxicity. Diltiazem, erythromycin, ketoconazole, mefloquine, quinine, and quinidine might also increase the toxicity of halofantrine because they have been shown to inhibit its metabolism in vitro. The manufacturer has therefore recommended caution with the concurrent use of potent CYP3A4 inhibitors. Fatty food markedly increases halofantrine levels, consequently it is recommended that halofantrine is taken on an empty stomach. Grapefruit juice has a similar effect Note that halofantrine is no longer widely marketed. 

In a preliminary study in healthy subjects, pyrimethamine/sulfadoxine (Fansidar) raised the AUCq. and peak plasma levels of halofantrine by about 1.6-fold, without changing the overall AUC. This might lead to an increased incidence of arrhythmias, see also (b) above. 

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