Etaquine or tafenoquine

Etaquine or tafenoquine is a new 8-aminoquinoline, derived from primaquine. It has a half-life of two weeks, which is much longer than the half-life of primaquine. It may be taken orally and has low toxicity. It is active against P. falciparum and P. vivax. It is an effective schizonticide and is also active on the pre-erythrocytic stages, including the hypnozoites of P. vivax.

The mechanism of action is still unclear, but it probably disturbs the action of the parasites’ mitochondria and the Golgi complex. There is also inhibition of the polymerisation of haematin to haemozoin (as with chloroquine). The product is administered as tafenoquine succinate. A dosage of 100 mg base corresponds to 125 mg salt. Ingestion with food increases the absorption by 50% and reduces the gastro-intestinal side effects. Absorption is slow, reaching a maximum plasma concentration after 12 hours. Tafenoquine is concentrated in red blood cells (3 times higher than in plasma).

Tafenoquine is not eliminated via the kidneys. The optimum curative dosage has not yet been determined, but 300 mg per day x 7 days yielded a cure rate of 100% (P. vivax). A possible role in the treatment of P. falciparum is being investigated, although problems with its slow onset of action have still be to overcome. It is also effective as a causal prophylactic agent. People with G6PD-deficiency may develop severe haemolysis after ingestion.

Development of methaemoglobinaemia (3-15% metHb) is common, but generally subclinical. Nevertheless account should be taken of this by mountain climbers, pilots or individuals with underlying cardiopulmonary disease. The product is not yet on the market.

Category: Medicine Notes