The resistance of Plasmodium falciparum to antimalarial drugs is one of the most worrisome problems in tropical medicine, but few clinical studies or observations have described confirmed cases of therapeutic failure.

We report two cases of in vivo P. falciparum resistance (RIII response) to quinine in French Guiana, an Amazonian focal zone in which multi-resistant malaria is endemic.

Both patients presented with uncomplicated malaria and were initially treated with intravenous quinine. Although absorption was normal, the treatment was not effective and the patients still had fever and significant parasitemia three days after the onset of treatment (day 3).

The addition of intravenous tetracycline completely resolved the parasitemia within approximately 96 hours.

These clinical reports confirm the necessity to combine quinine with tetracycline in this area, as recommended by the recent French regional antimalarial policy.