What is the recommended dose of Mefloquine (antimalarial medication) for prophylaxis and treatment?

Mefloquine Dosing for Malaria Prophylaxis and Treatment

For prophylaxis, adults should take 250 mg mefloquine weekly, starting 1-2 weeks before travel, continuing throughout exposure, and for 4 weeks after leaving the endemic area; for treatment of acute malaria, adults require 1250 mg (five 250 mg tablets) as a single oral dose. 1, 2

Prophylaxis Dosing

Adults

• 250 mg once weekly 1, 2
• Start 1-2 weeks before arrival in endemic area 1, 2
• Continue weekly on the same day each week, preferably after the main meal 2
• Must continue for 4 weeks after leaving the malarious area to ensure suppressive blood levels when merozoites emerge from the liver 1, 3, 2
• Always take with at least 8 oz (240 mL) of water and never on an empty stomach 1, 2

Pediatric Patients

• Approximately 5 mg/kg body weight once weekly 2
• Weight-based dosing for children under 45 kg: 2
  • Over 45 kg: one 250 mg tablet weekly
  • 30-45 kg: 3/4 tablet (187.5 mg) weekly
  • 20-30 kg: 1/2 tablet (125 mg) weekly
• Children under 15 kg (30 lbs): mefloquine is NOT recommended; use chloroquine instead 4, 3
• Tablets may be crushed and suspended in water, milk, or other beverage for children unable to swallow whole 2
• Experience in children weighing less than 20 kg is limited 2

Treatment Dosing

Adults

• 1250 mg (five 250 mg tablets) as a single oral dose 2
• Must be taken with at least 8 oz (240 mL) of water and not on an empty stomach 2
• If no improvement within 48-72 hours, do not use mefloquine for retreatment—switch to alternative therapy 2
• Critical caveat: If previous prophylaxis with mefloquine has failed, do NOT use mefloquine for curative treatment 1, 2

Pediatric Patients

• 20-25 mg/kg body weight 2
• Splitting the total dose into 2 doses taken 6-8 hours apart may reduce adverse effects 2
• Pediatric dose should never exceed the adult dose 2
• Safety and effectiveness in children under 6 months have not been established 2

Management of Vomiting During Treatment

• If vomiting occurs less than 30 minutes after dose: give a second full dose 2
• If vomiting occurs 30-60 minutes after dose: give an additional half-dose 2
• If vomiting recurs, monitor closely and consider alternative therapy if no improvement 2

Critical Contraindications

Absolute contraindications include: 4, 1

• History of seizures or epilepsy
• Active or history of serious psychiatric disorders (depression, psychosis, anxiety disorders)
• Severe liver impairment
• Hypersensitivity to mefloquine or related compounds
• Pregnancy (especially first trimester; can be used in second/third trimester if no alternative) 4, 1
• Children under 15 kg 4
• Travelers using beta blockers or drugs that alter cardiac conduction 4
• Travelers requiring fine coordination and spatial discrimination (e.g., airline pilots) 4

Important Safety Considerations

Neuropsychiatric Effects

• 70% of neuropsychiatric adverse events occur within the first three doses 1, 3
• Serious reactions (hallucinations, convulsions) are rare at prophylactic doses but more frequent at treatment doses 4
• Severe neuropsychiatric effects occur in approximately 0.01% of patients 1, 3
• Discontinue immediately if severe mood changes, hallucinations, or seizures develop 3

Drug Interactions

• Extreme caution required when using quinine to treat malaria in patients who have been taking mefloquine prophylaxis, due to similar pharmacology and cardiovascular/neurological toxicity 4

Special Populations

• Pregnancy: Avoid in first trimester; may use in second/third trimester if no alternative available 1
• Women of childbearing potential should use reliable contraception during prophylaxis and for 2 months after the last dose 4
• Not recommended during pregnancy for prophylaxis; pregnant women should use chloroquine for chloroquine-sensitive areas 4, 3

Post-Treatment Considerations

• For P. vivax malaria treated with mefloquine, patients are at high risk of relapse because mefloquine does not eliminate hepatic-phase parasites 2
• Must subsequently treat with primaquine (an 8-aminoquinoline) to prevent relapse 2
• For travelers with prolonged exposure to P. vivax and P. ovale, add primaquine 30 mg base daily during the last 2 weeks of the 4-week post-exposure period, but mandatory G6PD testing required before primaquine use 1, 3

Geographic Considerations

• Mefloquine is first-line for chloroquine-resistant areas such as sub-Saharan Africa and Southeast Asia 1
• Do NOT use mefloquine in mefloquine-resistant zones (particularly Thai-Burmese border region); use doxycycline 100 mg daily instead 1, 3
• Mefloquine resistance has developed rapidly in some areas despite combination therapy 5

Compliance and Storage

• Most malaria deaths occur in travelers who do not fully comply with prophylaxis regimens 3, 6
• The 4-week post-exposure continuation is critical—never stop early 3
• Overdose can be fatal; store in child-proof containers out of reach of children 4