indication

For the treatment of malaria.

pharmacology

Primaquine is an antimalarial agent and is the essential co-drug with chloroquine in treating all cases of malaria. In the blood, malaria parasites break down a part of the red blood cells known as haemoglobin. When this happens haemoglobin is divided into two parts; haem and globin. Haem is toxic to the malaria parasite. To prevent it from being damaged, the malaria parasite produces an chemical which converts the toxic haem into a non-toxic product. Primaquine acts by interfering with a part of the parasite (mitochondria) that is responsible for supplying it with energy. Without energy the parasite dies. This stops the infection from continuing and allows the person to recover. Primaquine kills the intrahepatic form of Plasmodium vivax and Plasmodium ovale, and thereby prevents the development of the erythrocytic forms that are responsible for relapses (it also kills gametocytes). Primaquine is not used in the prevention of malaria, only in the treatment. It has insignificant activity against the asexual blood forms of the parasite and therefore it is always used in conjunction with a blood schizonticide and never as a single agent. Primaquine has gametocytocidal activity against all plasmodia, including P. falciparum.

mechanism of action

Primaquine's mechanism of action is not well understood. It may be acting by generating reactive oxygen species or by interfering with the electron transport in the parasite. Also, although its mechanism of action is unclear, primaquine may bind to and alter the properties of protozoal DNA.

half life

3.7-7.4 hours

drug interactions

Artemether: Primaquine may increase the adverse effects of artemether. Combination therapy is contraindicated unless there are no other treatment options.

Lumefantrine: Primaquine may increase the adverse effects of lumefantrine. Combination therapy is contraindicated unless there are no other treatment options.

Tacrine: The metabolism of Tacrine, a CYP1A2 substrate, may be reduced by strong CYP1A2 inhibitors such as Primaquine. Consider modifying therapy to avoid Tacrine toxicity. Monitor the efficacy and toxicity of Tacrine if Primaquine is initiated, discontinued or if the dose is changed.

Thiothixene: The strong CYP1A2 inhibitor, Primaquine, may decrease the metabolism and clearance of Thiothixene, a CYP1A2 substrate. Consider alternate therapy or monitor for changes in Thiothixene therapeutic and adverse effects if Primaquine is initiated, discontinued or dose changed.

Tizanidine: Primaquine may decrease the metabolism and clearance of Tizanidine. Consider alternate therapy or use caution during co-administration.