Primaquine (Primaquine phosphate)

Product Information:

• Trade Name: Primaquine (primaquine phosphate)
• Strength: 26.3 mg primaquine phosphate (equivalent to 15 mg primaquine base)
• Manufacturer: Sanofi-aventis Canada Inc.

Indications:

• Primaquine is indicated for the radical cure (prevention of relapse) of Plasmodium vivax and Plasmodium ovale malaria.

Contraindications:

• Hypersensitivity to primaquine or any ingredient in the formulation.
• Acutely ill patients with systemic disease leading to granulocytopenia (e.g., rheumatoid arthritis, lupus erythematosus).
• Concurrent use with other hemolytic drugs or depressants of bone marrow.
• Recent use of quinacrine.
• Severe G6PD deficiency.
• Pregnant women.

Adult Dosage:

• Prevention: 30 mg base daily, starting one day before entering a malaria area, during exposure, and for 7 days after leaving.
• Terminal Prophylaxis (PART): 30 mg base/day for 14 days.
• Radical Cure: 30 mg base/day for 14 days.

Pediatric Dosage:

• Prevention: 0.5 mg base/kg daily (max 30 mg), starting one day before entering a malaria area, during exposure, and for 7 days after leaving.
• Terminal Prophylaxis (PART): 0.5 mg base/kg daily (max 30 mg) for 14 days.
• Radical Cure: 30 mg base/day for 14 days.

Advantage:

• Causal prophylaxis, only need to continue for 7 days after exposure.

Disadvantage:

• Requires G6PD testing.
• Daily dosing.

Adverse Effects:

• Occasional: GI upset, hemolysis in G6PD deficiency, methemoglobinemia.

Warnings and Precautions:

• Risk of hemolytic anemia in G6PD deficient patients; G6PD testing required before use.
• Monitor hematocrit and hemoglobin levels.
• Potential for QT interval prolongation; use with caution in patients with cardiac disease.
• Monitor for adverse reactions if used with other QT-prolonging drugs.
• Advise patients to seek immediate medical attention if symptoms of hemolytic anemia or methemoglobinemia occur.

Drug Interactions:

• Contraindicated with quinacrine.
• Avoid concurrent use with hemolytic agents or drugs prolonging the QT interval.
• Caution with CYP2D6 inhibitors (e.g., SSRIs) as they might impact primaquine metabolism.

Pharmacokinetics:

• Rapid absorption with peak plasma concentrations within 1-3 hours.
• High volume of distribution.
• Extensive metabolism primarily by CYP2D6.
• Minimal renal excretion.

Storage:

• Store between 15-30°C.
• Keep out of reach and sight of children.

Patient Advice:

• Take with food to reduce stomach upset.
• Use reliable contraception during and after treatment (2 menstrual cycles for women, 3 months for men).
• Stop treatment and seek medical help if experiencing symptoms of hemolytic anemia or methemoglobinemia.

Special Populations:

• Geriatrics: Monitor for efficacy and adverse reactions due to potential for decreased organ function.
• Hepatic and Renal Impairment: Monitor for adverse reactions; pharmacokinetics may be affected.