What is the recommended treatment regimen for Plasmodium Vivax (malaria) infection?

Treatment Regimen for Plasmodium Vivax Malaria

The recommended treatment regimen for Plasmodium vivax malaria consists of chloroquine (25 mg base/kg over 3 days) for blood stage parasites followed by primaquine (15 mg base daily for 14 days) for radical cure of liver hypnozoites. 1

Blood Stage Treatment

• Chloroquine phosphate dosing schedule:

  • Total dose: 25 mg base/kg divided over 3 days
  • Adult dosing: 600 mg base initially, followed by 300 mg at 24 and 48 hours (total 1500 mg) 2, 1
  • Children: 10 mg/kg initially, 10 mg/kg at 24 hours, and 5 mg/kg at 48 hours 2

• Alternative for chloroquine-resistant areas:

  • Atovaquone-proguanil (Malarone™) for 3 days 2
  • Dihydroartemisinin-piperaquine (preferred ACT due to longer half-life) 1

Liver Stage Treatment (Radical Cure)

• Primaquine phosphate:

  • Standard dosing: 15 mg base daily for 14 days (adults) 2, 1
  • Pediatric dosing: 0.3 mg/kg/day for 14 days 2
  • Purpose: Eradicate liver hypnozoites to prevent relapse 3

• Alternative radical cure option:

  • Tafenoquine 300 mg single dose (requires quantitative G6PD testing) 1

Important Considerations

G6PD Testing

• G6PD testing is essential before administering primaquine or tafenoquine 1
• For patients with severe G6PD deficiency, primaquine should not be administered for more than 5 days due to risk of life-threatening hemolysis 2
• For intermediate G6PD deficiency (30-70%), weekly primaquine (0.75 mg base/kg, maximum 45 mg) for 8 weeks with close monitoring is recommended 1

Pregnancy and Breastfeeding

• Primaquine and tafenoquine are contraindicated during pregnancy and breastfeeding 1
• Chloroquine is safe during pregnancy 2

Treatment Monitoring

• Patients should be monitored for clinical response
• If symptoms persist beyond 48-72 hours after starting chloroquine, consider treatment failure and switch to alternative therapy 2

Alternative Regimens

Research has evaluated shorter primaquine regimens:

• 0.5 mg/kg/day for 7 days (same total dose as 14-day regimen) may be as effective as the standard 14-day regimen with similar relapse rates 4
• 5-day primaquine regimens have significantly higher relapse rates compared to 14-day regimens (28.4% vs 13.6%) and should be avoided 5

Treatment of Chloroquine-Resistant P. vivax

For areas with known chloroquine resistance:

• Chloroquine plus primaquine combination therapy has shown effectiveness (5% failure rate at 14 days) 6
• Atovaquone-proguanil (Malarone™) is recommended as an alternative 2
• Halofantrine has shown efficacy (0% failure at 14 days) but is not widely used due to cardiac concerns 6

Common Pitfalls to Avoid

1. Failure to test for G6PD deficiency before administering primaquine, which can cause severe hemolysis in deficient individuals
2. Inadequate dosing or duration of primaquine therapy, leading to relapse
3. Not considering regional resistance patterns when selecting therapy
4. Incomplete treatment course - emphasize the importance of completing the full 14-day primaquine regimen despite symptom resolution
5. Overlooking contraindications such as pregnancy or severe G6PD deficiency

The 14-day primaquine regimen remains the gold standard for preventing P. vivax relapse, with evidence confirming its superiority over shorter courses 3. While shorter regimens may improve adherence, they must maintain the same total dose to be effective.