What are the recommended oral drugs for treating Plasmodium vivax malaria?

Recommended Oral Drugs for Plasmodium vivax Malaria

Chloroquine is the drug of choice for treating uncomplicated Plasmodium vivax malaria, followed by primaquine for radical cure to prevent relapses, with G6PD testing required before primaquine administration. 1

Blood-Stage Treatment Options

First-Line Treatment

• Chloroquine (in chloroquine-sensitive regions) 1, 2
  • Adult dosing: Total dose of 25 mg/kg base over 3 days
    • Day 1: 600 mg (10 mg/kg)
    • Day 2: 600 mg (10 mg/kg)
    • Day 3: 300 mg (5 mg/kg)
  • Should be taken with food and water
  • Effective against blood-stage parasites but does not eliminate liver hypnozoites

Alternative Options (for chloroquine-resistant areas)

• Artemisinin-based combination therapies (ACTs) 1, 2

  • Dihydroartemisinin-piperaquine (DHA-PPQ): 3 tablets daily for 3 days in fasting condition
  • Artemether-lumefantrine (AL): 4 tablets at 0,8,24,36,48, and 60 hours with fatty meal
  • Consider for patients from known chloroquine-resistant areas (Papua New Guinea, Indonesia, Sabah) 1

• Mefloquine 3

  • Adult dose: Five tablets (1250 mg) as single oral dose
  • Take with at least 8 oz (240 mL) of water, not on empty stomach
  • Not recommended if treatment fails within 48-72 hours

• Atovaquone-proguanil 2

  • Alternative when ACTs are contraindicated

Anti-Relapse Treatment (Radical Cure)

Standard Regimen

• Primaquine 1, 2, 4
  • Adult dose: 15 mg base daily for 14 days (standard dose)
  • Alternative: 30 mg base daily for 14 days (high-standard dose)
  • MANDATORY: G6PD testing required before administration 1, 2
  • Contraindicated in pregnancy 1
  • Should be administered concurrently with blood schizontocidal drug 4

Alternative Primaquine Regimens

• For patients with mild to moderate G6PD deficiency (30-70% activity): 45 mg once weekly for 8 weeks 1
• Short course option: 0.5 mg/kg/day for 7 days (same total dose as standard 14-day course) 5

Newer Option

• Tafenoquine 2, 6
  • Single 300 mg dose
  • MANDATORY: G6PD testing required before administration 2
  • Not available in all regions
  • May be more effective than primaquine for preventing relapses in some cases 6

Important Considerations

G6PD Testing

• G6PD testing is mandatory before administering primaquine or tafenoquine 1, 2
• Risk of life-threatening hemolysis in G6PD-deficient patients 1
• In populations with high prevalence of G6PD deficiency (notably Asians), primaquine should not be administered for more than 5 days without G6PD testing 1

Monitoring and Follow-up

• Monitor patients for 48-72 hours after initiating treatment 1
• If symptoms persist beyond this period, consider treatment failure and switch to alternative therapy 1
• Monitor for post-artemisinin delayed hemolysis (PADH) when using ACTs, which occurs in 1.9-37.4% of patients 1

Special Populations

• Pregnant women: Primaquine and tafenoquine are contraindicated 1

  • Treat with chloroquine alone during pregnancy 1
  • Defer anti-relapse therapy until after pregnancy

• Children: Weight-based dosing 1, 3

  • Chloroquine: 10 mg/kg on days 1-2,5 mg/kg on day 3
  • Primaquine: 0.3 mg/kg/day for 14 days

Treatment Challenges

Resistance Patterns

• Chloroquine resistance in P. vivax is documented in Papua New Guinea, Indonesia, and Sabah 1
• Consider ACTs for patients from these regions 1
• Treatment failure rates should be <10% to be considered effective 2

Relapse Prevention

• Without anti-relapse therapy, P. vivax has high relapse rates (9.3% in one study) 1
• Primaquine reduces relapse risk by approximately 80% 1
• Combination of chloroquine and primaquine significantly reduces therapeutic failure compared to chloroquine alone (15% vs 78% at 28 days) 7

By following this treatment algorithm for P. vivax malaria, clinicians can effectively manage both the acute blood-stage infection and prevent relapses through appropriate radical cure, ultimately reducing morbidity and mortality associated with this infection.