• Treatment of uncomplicated Plasmodium falciparum malaria
  • Often used in combination with artesunate in artemisinin-based combination therapy (ACT)

Adult Dosing (when used with artesunate):

  • Sulfamethoxypyrazine 500 mg + Pyrimethamine 25 mg OD for 3 days
  • Usually co-administered with Artesunate 100 mg OD for 3 days

Pediatric Dosing:

  • Weight-based dosing in fixed-dose combinations
  • For example:
    • 250 mg sulfamethoxypyrazine + 12.5 mg pyrimethamine (per tablet) for smaller children
    • Dose given OD for *3/7

Common tablet formulations:

  • Sulfamethoxypyrazine 500 mg + Pyrimethamine 25 mg
  • Pediatric strengths: 250 mg + 12.5 mg
  • Available as fixed-dose combinations or as part of SP-Artesunate combinations
  • Administer once daily (OD) for 3 consecutive days
  • Should be taken with food to reduce gastrointestinal discomfort
  • Ensure adequate hydration to minimize risk of crystalluria from the sulfonamide component

Class:

  • Sulfamethoxypyrazine: Sulfonamide (antifolate)
  • Pyrimethamine: Diaminopyrimidine (antifolate)

Mechanism of Action:

  • Sulfamethoxypyrazine inhibits dihydropteroate synthase, blocking folate synthesis
  • Pyrimethamine inhibits dihydrofolate reductase, further blocking folate utilization
  • The dual blockade disrupts DNA synthesis in the malaria parasite

Pharmacokinetics:

  • Sulfamethoxypyrazine: Long half-life (~100 hours), allowing once-daily dosing
  • Pyrimethamine: Long half-life (~96 hours); good oral absorption
  • Nausea, vomiting, abdominal pain
  • Skin rash, urticaria
  • Rare but serious: Stevens-Johnson syndrome, toxic epidermal necrolysis
  • Bone marrow suppression (with high or prolonged use): anemia, thrombocytopenia
  • Hepatotoxicity (rare)
  • Hypersensitivity to sulfonamides or pyrimethamine
  • History of severe skin reactions to sulfa drugs
  • Megaloblastic anemia due to folate deficiency
  • Additive toxicity with other antifolates (e.g., co-trimoxazole)
  • Anticonvulsants (phenytoin): pyrimethamine may displace protein binding
  • May interact with methotrexate (increased antifolate effects)

                                   Drug Status

Availability
Pregnancy
Breastfeeding
Schedule
BRAND NAME STRENGTH FORMULATION PACK SIZE MANUFACTURER DISTRIBUTOR
Ekelfin 500mg/25mg Tablet 2’s Elys Chemicals Elys Chemicals
Laefin 500mg/25mg Tablet 2’s Laboratory & Allied Laboratory & Allied
Malafin 500mg/25mg Tablet 30’s Universal Corporation Universal Corporation