Treatment for Eradicating Vivax Malaria
For radical cure of P. vivax malaria, administer chloroquine 25 mg/kg base over 3 days for blood-stage parasites, followed by primaquine 0.5 mg/kg/day (maximum 30 mg base daily) for 14 days to eradicate liver hypnozoites—but only after confirming normal G6PD status. 1, 2, 3
Pre-Treatment Requirements
G6PD testing is absolutely mandatory before any primaquine administration. 1, 2 Failure to test for G6PD deficiency risks life-threatening hemolytic anemia, particularly in populations with high rates of severe deficiency (notably Asian populations). 4
Exclude pregnancy and breastfeeding. 4, 1, 2 Primaquine is contraindicated in pregnant women, lactating mothers, and infants under 6 months. 1
Blood-Stage Treatment (Chloroquine)
In chloroquine-sensitive areas, administer:
- Adults: 600 mg base initially, then 600 mg at 24 hours, then 300 mg at 48 hours (total 1,500 mg base over 3 days) 4
- Children: 10 mg/kg base at 0 and 24 hours, then 5 mg/kg at 48 hours (total 25 mg/kg) 4
Start primaquine concurrently with chloroquine, not after completion. 3 Co-administration boosts primaquine blood levels and enhances efficacy. 1, 2
Radical Cure with Primaquine (Anti-Relapse Therapy)
Standard High-Dose Regimen (Preferred)
0.5 mg/kg/day (30 mg base for adults) for 14 days 1, 2
- This high-standard dose provides 80% risk reduction in relapse compared to no primaquine 1, 2
- Well-tolerated in G6PD-normal individuals with comparable safety to lower doses 1
- Particularly important for Southeast Asian strains, which may be resistant to lower doses 1
Alternative Standard Regimen
0.25 mg/kg/day (15 mg base for adults) for 14 days 3, 5
- FDA-approved standard dose 3
- May be insufficient for Southeast Asian strains 1
- Confirmed effective in preventing relapses (RR 0.6 vs. no primaquine) 5
Pediatric Dosing
0.3 mg/kg/day for 14 days 4, 1
Modified Regimens for Special Populations
Mild-to-Moderate G6PD Deficiency (30-70% activity, A- variant)
45 mg base once weekly for 8 weeks 1
- Reduces hemolysis risk while maintaining anti-hypnozoite efficacy 1
- Requires close monitoring for hemolysis 1
Severe G6PD Deficiency (Mediterranean B- variant)
Primaquine is contraindicated. 1 Even extended dosing regimens carry very high risk of severe hemolysis. 1
Asian Populations Without G6PD Testing
Do not administer primaquine for more than 5 days without confirmed G6PD status. 4 Severe G6PD deficiency is notably common in Asian populations. 4
Monitoring and Follow-Up
Monitor for hemolysis signs during the first week: dark urine, jaundice, fatigue. 1
Clinical improvement should occur within 48 hours of starting chloroquine treatment. 2
Repeat thick blood smear at day 3 if symptoms persist—consider chloroquine resistance and switch to alternative therapy (artemisinin-based combination therapy, mefloquine, or quinine). 4
Follow-up extends 6-12 months to detect relapses, though most occur within the first 3 months. 5, 6
Chloroquine-Resistant Areas
In regions with documented chloroquine resistance (Papua New Guinea, Indonesia):
- Use artemisinin-based combination therapy (ACT) such as dihydroartemisinin-piperaquine or artemether-lumefantrine for blood-stage treatment 4
- Still combine with primaquine 0.5 mg/kg/day for 14 days for radical cure 4, 1
Common Pitfalls to Avoid
Do not skip G6PD testing. This is the most critical error—administering primaquine without knowing G6PD status can cause fatal hemolysis. 1, 2
Do not delay primaquine until after chloroquine completion. Concurrent administration is recommended and enhances efficacy. 1, 2, 3
Do not use shorter primaquine courses (5-7 days at standard dose) expecting equivalent efficacy. Five-day regimens have 10-fold higher relapse rates (RR 10.05) compared to 14-day treatment. 5
Do not forget pregnancy screening. Primaquine must be deferred until after delivery. 1, 2
Do not assume all vivax is chloroquine-sensitive. Resistance is documented in Indonesia, Papua New Guinea, and parts of Southeast Asia—use ACTs in these regions. 4, 7