Primaquine phosphate is indicated for:

• Radical cure of Plasmodium vivax and Plasmodium ovale malaria
• As a gametocytocidal agent in P. falciparum infections
• Terminal prophylaxis after leaving a malaria-endemic area

Each film-coated tablet contains Primaquine Phosphate BP 26.4 mg (equivalent to Primaquine 15 mg)

Primaquine Phosphate is an 8-aminoquinoline derivative used orally for the radical cure of vivax and ovale malaria and to prevent relapse after treatment with a blood schizontocide.

It is also used to prevent the transmission of falciparum malaria in individuals returning to areas where reintroduction of malaria is possible. Pharmacokinetic properties:

• Presystemic metabolism: Extensive
• Plasma half-life: 4–10 hours (average about 6 hours)
• t½: approximately 1–2 hours
• Plasma protein binding: High

The dose of primaquine deployed depends upon the indication for use and the glucose-6-phosphate dehydrogenase (G6PD) status of the patient. Terminal prophylaxis with primaquine is indicated only for selected group of travellers e.g. those who have had prolonged exposure in malaria endemic areas. In the radical cure of vivax and ovale malaria, primaquine should be given after appropriate therapy with chloroquine. The conventional adult dose for prevention of relapse is 15 mg base daily for 14 days. Higher doses, 30 mg base daily for 14 days, can be given to deal with less sensitive strains of the parasites, provided the patient's G6PD is normal; however, the higher dosage regimen should not be used routinely. A suggested dose for children is 200 to 300 mcg per kg body-weight daily for 14 days.

In patients with G6PD deficiency haemolysis due to primaquine is less when the drug is administered at intervals rather than on a daily basis, so that the preferred regimen is 45 mg base once weekly for 8 weeks, or 30 mg base once weekly for 15 weeks, according to the type of G6PD deficiency. Strict medical supervision is essential.

For use as a gametocytocide in P. falciparum, it is given as a single dose of 30-40 mg base for adults.

Use in children: In view of the relative toxicity of primaquine, it should not be given to children under one year of age. Older children can receive primaquine, under careful medical supervision.

Primaquine may reduce hepatic drug metabolism and has been reported to slow the breakdown of chloroquine in the body.

• Primaquine is contraindicated during pregnancy and breastfeeding.
• It should not be used in patients with acute flare-ups of systemic diseases associated with granulocytopenia, such as rheumatoid arthritis and lupus erythematosus.
• It is also contraindicated when used together with other medicines that may cause hemolysis or bone marrow suppression.

At therapeutic doses, side effects are usually mild, but abdominal pain and gastric discomfort may occur, especially if taken on an empty stomach.
Higher doses may cause nausea and vomiting. Methemoglobinemia may occasionally occur. Hemolytic anemia may develop in patients with G6PD deficiency.
Other less common effects include mild anemia and leukocytosis. Rarely, hypertension and cardiac arrhythmias have been reported.

This medicine is contraindicated during pregnancy because it may cross the placenta and cause hemolytic anemia in a G6PD-deficient fetus.
It is excreted into breast milk, therefore mothers taking this medicine should avoid breastfeeding.

Use with caution in patients with systemic diseases associated with granulocytopenia and in those with known or suspected G6PD deficiency. Primaquine should be stopped immediately if signs of hemolysis or methemoglobinemia appear. Blood counts should be checked regularly during treatment.

Symptoms of overdose may include abdominal cramps, vomiting, burning pain in the stomach, central nervous system and cardiovascular disturbances including cardiac arrhythmia and QT interval prolongation, cyanosis, methemoglobinemia, leukocytosis or leukopenia, and anemia. The most serious effects are granulocytopenia and acute hemolytic anemia, especially in G6PD-deficient patients. Recovery is usually complete after stopping the medicine.

Anti-malarial drugs

Store at 25°C. Protect from light.