Primaquine

Primaquine phosphate Tablets are indicated for the radical cure (prevention of relapse) of vivax malaria.

Primaquine phosphate is an 8-aminoquinoline antimalarial drug. The mechanism of action has not been fully established. The major assumptions are an inhibition of the mitochondrial system of dormant parasites, and an oxidative stress generated through reactive metabolites in infected cells. In humans, primaquine phosphate activity is probably related to hydroxylated metabolites generated intrahepatically by CYP2D6.

Primaquine phosphate Tablets are recommended only for the radical cure of vivax malaria, the prevention of relapse in vivax malaria, or following the termination of chloroquine phosphate suppressive therapy in an area where vivax malaria is endemic. Patients suffering from an attack of vivax malaria or having parasitized red blood cells should receive a course of chloroquine phosphate, which quickly destroys the erythrocytic parasites and terminates the paroxysm. Primaquine phosphate Tablets should be administered concurrently to eradicate the exoerythrocytic parasites in adults at a dosage of 1 tablet (equivalent to 15 mg base) daily for 14 days. Primaquine phosphate Tablets can be taken with or without food. Administration of Primaquine phosphate Tablets with food may reduce the incidence of gastrointestinal symptoms.

Known hypersensitivity reactions to primaquine phosphate, other 8- aminoquinolones, or to any component in Primaquine phosphate Tablets. Severe glucose-6-phosphate dehydrogenase (G6PD) deficiency. Pregnant women. Breastfeeding by a lactating woman when the infant is found to be G6PD deficient or if G6PD status is unknown. Because quinacrine hydrochloride appears to potentiate the toxicity of antimalarial compounds which are structurally related to primaquine, the use of quinacrine in patients receiving Primaquine phosphate Tablets is contraindicated. Similarly, Primaquine phosphate Tablets should not be administered to patients who have received quinacrine recently, as toxicity is increased.

Hemolytic Anemia Hemolytic reactions (moderate to severe) may occur in individuals with G6PD deficiency and in individuals with a family or personal history of favism. Areas of high prevalence of G6PD deficiency are Africa, Southern Europe, Mediterranean region, Middle East, South-East Asia, and Oceania. People from these regions have a greater tendency to develop hemolytic anemia due to a congenital deficiency of erythrocytic G6PD while receiving primaquine and related drugs. Due to the risk of hemolytic anemia in patients with G6PD deficiency, G6PD testing must be performed before using primaquine. Before initiating treatment, obtain baseline hemoglobin and hematocrit. In case of severe anemia, postpone the G6PD test and decision on treatment with primaquine until recovery.

Gastrointestinal: Nausea, vomiting, epigastric distress, abdominal cramps. Hematologic: Leukopenia, hemolytic anemia, decreased hemoglobin, methemoglobinemia. Hemolytic anemia occurs commonly in patients with G6PD deficiency and may be severe or fatal in patients with severe G6PD deficiency. Methemoglobin levels are usually <10%, but methemoglobinemia may be severe in nicotinamide adenine dinucleotide (NADH) methemoglobin reductase deficient individuals or in patients with other risk factors. Leukopenia was observed in patients with rheumatoid arthritis or lupus erythematosus. Cardiac: Cardiac arrhythmia and QT interval prolongation. Nervous System: Dizziness. Skin and Soft Tissue: Rash, pruritus.

Pharmacodynamics Interactions Quinacrine Concurrent use of quinacrine (mepacrine) and Primaquine phosphate Tablets are contraindicated. Increased toxicity was seen when quinacrine was used with pamaquine, another 8-aminoquinoline. Hemolytic Agents and Methemoglobinemia-Inducing Drugs The concurrent administration of hemolytic agents or methemoglobinemia-inducing drugs and primaquine should be avoided. If the concurrent administration cannot be avoided, close blood monitoring is required. QT Interval Prolonging Drugs The pharmacodynamic interaction potential to prolong the QT interval of the electrocardiogram between Primaquine phosphate Tablets and other drugs that effect cardiac conduction is unknown. If Primaquine phosphate Tablets are used concomitantly with other drugs that prolong the QT interval, close and frequent electrocardiogram monitoring is advised.

Store at 25° C (77° F), excursions permitted to 15° C – 30° C (59° F – 86° F) Dispense in tight, light-resistant container as defined in the USP/NF.