DrugindexOnline^{2nd edition}

Pronouncation: (PRIM-uh-kween FOSS-fate)
Class: Antimalarial

Trade Names:
Primaquine Phosphate
- Tablets 26.3 mg (equiv. to 15 mg base)

Mechanism of Action

Pharmacology

Disrupts metabolic processes of parasitic organism, eliminating tissue (exoerythrocytic) infection and preventing development of blood (erythrocytic) forms of parasite responsible for relapses of vivax malaria.

Pharmacokinetics

Absorption

Rapid. Bioavailability is approximately 96%. T _max is approximately 2 to 3 hr (primaquine), approximately 7 hr (metabolite carboxyprimaquine). C _max is 50 to 66 ng/mL (15 mg); 104 ng/mL (30 mg).

Distribution

Extensively distributed. Vd is 248 L. C _max is 291 to 736 ng/mL (metabolite) and 432 to 1240 ng/mL (metabolite).

Metabolism

Rapidly converted to carboxyprimaquine. Undetermined if the main plasma metabolite has activity.

Elimination

Urine (less than 2% of dose). The t _½ is 5.8 hr (primaquine); 22 to 30 hr (metabolite carboxyprimaquine).

Indications and Usage

Radical cure or prevention of relapse in vivax malaria; after termination of chloroquine phosphate suppressive therapy in areas where vivax malaria is endemic.

Unlabeled Uses

With clindamycin, treatment of Pneumocystis carinii pneumonia associated with AIDS.

Contraindications

Concomitant administration of quinacrine and primaquine; acutely ill patient with systemic disease manifested by granulocytopenia (eg, rheumatoid arthritis, lupus erythematosus); concurrent administration of other potentially hemolytic or bone marrow depressant medications.

Dosage and Administration

Begin therapy during last 2 wk of or after course of suppression with chloroquine or comparable drug.

Adults

PO 26.3 mg (15 mg base) for 14 days.

Children

PO 0.5 mg/kg/day (0.3 mg/kg/day of base) for 14 days (max, 15 mg/day of base).

General Advice

Administer without regard to meals. Administer with food if GI upset occurs.

Storage/Stability

Store at room temperature in tightly closed, light-resistant container.

Drug Interactions

Quinacrine

May potentiate toxicity of antimalarial compounds that are structurally related to primaquine.

Laboratory Test Interactions

None well documented.

Adverse Reactions

GI

Nausea; vomiting; epigastric distress; abdominal cramps.

Hematologic

Leukopenia; hemolytic anemia in G-6-PD deficiency; methemoglobinemia in NADH methemoglobin reductase deficiency.

Precautions

Pregnancy

Pregnancy category undetermined.

Lactation

Undetermined. To avoid adverse effects in the infant, do not give to lactating women.

Hemolytic anemia

May occur in patients with following conditions: G-6-PD deficiency, NADH methemoglobin reductase deficiency; idiosyncratic reactions (leukopenia, methemoglobinemia; hemolytic anemia). Discontinue drug if marked darkening of urine or sudden decrease in hemoglobin or leukocyte count occurs.

Max dose

Hemolytic reactions may occur with doses of drug exceeding recommended dose.

Overdosage

Symptoms

Anemia, methemoglobinemia, leukopenia, acute abdominal cramps, vomiting, epigastric distress, CNS and cardiovascular disturbances, granulocytopenia, hemolytic anemia.

Patient Information

• Tell patient that medicine may be taken with food if stomach upset (eg, nausea, vomiting, abdominal cramps) occurs, and advise patient to contact health care provider if upset persists.
• Emphasize importance of compliance with drug regimen.
• Advise patient to report marked darkening of urine to health care provider.