What is the recommended treatment regimen for Plasmodium vivax (P.vivax) malaria?

Treatment Regimen for Plasmodium vivax Malaria

The recommended treatment regimen for Plasmodium vivax malaria consists of chloroquine for blood stage parasites (25 mg base/kg over 3 days) followed by primaquine (15 mg base daily for 14 days) for radical cure of liver hypnozoites. 1, 2, 3

Blood Stage Treatment

First-line therapy:

• Chloroquine phosphate (if acquired outside chloroquine-resistant areas)
  • Dosing: Total of 25 mg base/kg over 3 days
  • Adult dosing schedule: 600 mg base initially, followed by 300 mg at 6,24, and 48 hours 1, 2
  • Common side effects: Nausea, vomiting, pruritus

Alternative therapy (for chloroquine-resistant areas):

• Dihydroartemisinin-piperaquine (DHAePPQ) - preferred ACT due to longer half-life 1
• Artemether-lumefantrine (AL)
• Atovaquone-proguanil (A-P)
• Mefloquine (MQ)

Radical Cure (for liver hypnozoites)

Standard regimen:

• Primaquine phosphate
  • Dosing: 15 mg base daily for 14 days 2, 3
  • Timing: Should be administered concurrently with chloroquine 3
  • CRITICAL: G6PD testing is required before administration 2

Alternative for G6PD intermediate deficiency:

• For those with intermediate G6PD deficiency (>30% < 70%) and non-Mediterranean variant (A-):
  • Weekly primaquine (0.75 mg base/kg, maximum 45 mg) for 8 weeks with close monitoring for hemolysis 1

Alternative single-dose option:

• Tafenoquine 300 mg single dose
  • Only available in the US and Australia
  • Requires quantitative G6PD testing (do not use if <70%)
  • FDA restricts co-administration with chloroquine only 1, 2

Treatment for Severe P. vivax Malaria

If the patient presents with severe malaria:

• Intravenous artesunate (first-line): 2.4 mg/kg IV at 0,12, and 24 hours, then daily 1
• Alternative: IV quinine dihydrochloride if artesunate unavailable 1
• Switch to oral therapy when patient can tolerate it

Important Considerations and Monitoring

• G6PD testing: Mandatory before primaquine or tafenoquine administration to prevent hemolysis 2
• Contraindications: Primaquine and tafenoquine are contraindicated during pregnancy and breastfeeding 1, 2
• Monitoring: Check parasitemia every 24 hours until negative for uncomplicated malaria 2
• Treatment failure: Consider if symptoms persist after 48-72 hours of chloroquine treatment 2

Pitfalls to Avoid

1. Failure to provide radical cure: Without primaquine/tafenoquine, P. vivax will relapse from dormant liver stages 4, 5
2. Administering primaquine without G6PD testing: Can cause severe hemolysis in G6PD-deficient patients
3. Underestimating P. vivax severity: Though often considered "benign," P. vivax can cause severe illness and death, particularly in those with comorbidities 6
4. Ignoring chloroquine resistance: In areas like Papua New Guinea and Indonesia, chloroquine resistance is prevalent and ACTs should be used instead 1
5. Missing concurrent infections: P. vivax and P. falciparum co-infections can occur and require appropriate treatment for both species

P. vivax malaria requires a two-pronged approach targeting both blood and liver stages to prevent both acute illness and future relapses, making it more challenging to eliminate than P. falciparum in many settings 5.