OralChloroquine resistant falciparum malaria acute attackAdult: Per tab contains pyrimethamine 25 mg and sulfadoxine 500 mg: 2-3 tabs as a single dose. Do not repeat for at least 7 days.
Child: Pyrimethamine 25mg + Sulfadoxine 500mg (Tablet): <2 yr (5-10 kg): ½ tab as a single dose; 2-5 yr (>10-20 kg): 1 tab as a single dose; 5-10 yr (< 20-30 kg): 1½ tab as a single dose; 10-14 yr (> 30-45 kg): 2 tab as a single dose. Do not repeat for at least 7 days.
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Dose reduction may be needed. Severe: contra-indicated.
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Dose reduction may be needed. Severe: contra-indicated.
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Should be taken with food. Take w/ plenty of fluids. Swallow whole, do not chew/crush.
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Severe renal or hepatic impairment, blood dyscrasias, hypersensitivity to components, megaloblastic anaemia due to folate deficiency, pregnancy at term and during lactation, infants ≤ 2 mth old.
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Impaired renal or hepatic function, folate deficiency, severe allergy or bronchial asthma, G6PD deficiency, pregnancy. Take with plenty of water to prevent crystalluria. Avoid excessive exposure to sun. Discontinue at the first sign of rash. Discontinue if signs of folic acid deficiency develops. Regular CBC monitoring, LFT, analysis of urine for crystalluria when admin for > 3 mth. Take with food to minimise Gi effects (e.g. anorexia and vomiting).
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Urticaria, serum sickness, photosensitisation, arthralgia, nausea, vomiting, abdominal pain, diarrhoea, headache, peripheral neuritis, ataxia, tinnitus, vertigo, convulsions, toxic nephrosis and pulmonary infiltrates resembling eosinophilic or allergic alveolitis.
Potentially Fatal: Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, blood dyscrasias, anaphylactoid reactions.
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Symptoms: Headache, nausea, anorexia, vomiting, CNS stimulation, megaloblastic anaemia, leukopenia, thrombocytopenia, glossitis and crystalluria. Management: Treatment is symptomatic and supportive. Emesis and gastric lavage to reduce drug absorption. Ensure that patient is adequately hydrated to prevent kidney damage. Monitor renal, hepatic, and haematopoietic systems for at least 1 month after overdosage. Folinic acid may be admin for depressed platelet or WBC counts.
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Increased halofantrine and chlorpromazine levels. Increased effects of warfarin.
Potentially Fatal: Increased risk of myelosupression with zidovudine, clozapine.
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Description:
Mechanism of Action: Pyrimethamine, a folic acid antagonist, inhibits the reduction of dihydrofolic acid to tetrahydrofolic acid (folinic acid). Sulfadoxine, a structural analog of p-aminobenzoic acid (PABA), competitively inhibits dihydrofolic acid synthesis which is important for PABA conversion to folic acid. This combination results in a synergistic action against susceptible plasmodia. Both have prolonged half-lives enabling single dose admin.
Pharmacokinetics:
Absorption: Peak plasma concentration: 4 hr.
Distribution: Volume of distribution: 0.14 L/kg (sulfadoxine); 2.3 L/kg (pyrimethamine). Protein binding: 90% (for both drugs). Both drugs cross placenta and passes into breast milk.
Metabolism: Sulfadoxine: 5% appear in blood as acetylated metabolite, 2-3% as glucuronide. Pyrimethamine converted to several metabolites.
Excretion: Elimination half life: 100 hr (pyrimethamine); 200 hr (sulfadoxine). Excreted mainly via kidneys.
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