Co-administration with halofantrine, another antimalarial, is also to be avoided because of the effect both drugs may have on cardiac rhythm. On their own, both of these two drugs effectively prevent attacks of malaria in chloroquine sensitive areas. In combination they provide reasonable protection in areas of limited to moderate chloroquine resistant falciparum, although less than that of mefloquine. Minor side effects include mouth ulcers, gastrointestinal upsets and exacerbation of psoriasis. Retinal toxicity from chloroquine is related to much higher doses than those used in malaria prophylaxis.
Epilepsy is a relatively strong contraindication, in common with mefloquine.
Both can be taken for a continuous period of five years without any apparent ill effects. It is a useful alternative, in combination with chloroquine, to mefloquine in areas of chloroquine resistant falciparum. Agranulocytosis is the main risk and has been reported relatively frequently when the dose of one tablet weekly has been exceeded. This is a useful drug in areas where both mefloquine and chloroquine resistance coexist. In practice, this means rural parts of Thailand, Cambodia and Myanmar.