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Sulfadoxine + Pyrimethamine information from DrugsUpdate  

See Available Brands of Sulfadoxine + Pyrimethamine in India

P - Caution when used during pregnancy
L - Contraindicated in lactation

Both drugs are antifolates; they inhibit the production of enzymes involved in the synthesis of folic acid within the parasites. Either drug by itself is only moderately effective in treating malaria, because the parasite Plasmodium falciparum may be able to use exogenous folic acid, i.e. folic acid which is present in the parasite's environment, while in combination, the two substances have a synergistic effect which outbalances that ability.

The combination is considered to be more effective in treating malaria caused by Plasmodium falciparum than that caused by Plasmodium vivax, for which chloroquine is considered more effective, though in the absence of a species-specific diagnosis the sulfadoxine-pyrimethamine combination may be indicated. Due to side effects, however, it is no longer recommended as a routine preventative, but only to treat serious malaria infections or to prevent them in areas where other drugs may not work.

Pharmacodynamics

Pharmacokinetics

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.

Absorption

Peak plasma concentration: 4 hours.

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 hours (pyrimethamine); 200 hours (sulfadoxine). Excreted mainly via kidneys.

Sulfadoxine + Pyrimethamine Indications / Sulfadoxine + Pyrimethamine Uses

Information Not Available

Sulfadoxine + Pyrimethamine Adverse Reactions / Sulfadoxine + Pyrimethamine Side Effects

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.

Precautions

Warnings
Fatalities have occurred because of severe reactions, including Stevens-Johnson syndrome and TEN. Discontinue sulfadoxine/pyrimethamine prophylaxis at the first appearance of skin rash, if a significant reduction in the count of any formed blood elements is noted, or upon the occurrence of active bacterial or fungal infections.

Monitor
Regularly schedule liver enzyme tests, analysis of urine for crystalluria, and CBCs whenever administration is for more than 3 months.

Overdosage

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.

Special Precautions

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 months. Take with food to minimise GI effects (e.g. anorexia and vomiting).

Other Drug Interactions

Increased halofantrine and chlorpromazine levels. Increased effects of warfarin.

Potentially Fatal: Increased risk of myelosupression with zidovudine, clozapine.

Other Interactions

Information Not Available

Dosage

Oral
Chloroquine resistant falciparum malaria acute attack
Adult: 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 years (5-10 kg): ½ tab as a single dose; 2-5 years (>10-20 kg): 1 tab as a single dose; 5-10 years (< 20-30 kg): 1½ tab as a single dose; 10-14 years (> 30-45 kg): 2 tab as a single dose. Do not repeat for at least 7 days.

Renal impairment: Dose reduction may be needed. Severe: contra-indicated.
Hepatic impairment: Dose reduction may be needed. Severe: contra-indicated.

Food(before/after)

Information Not Available

List of Contraindications

Sulfadoxine + Pyrimethamine and Pregnancy

Caution when used during pregnancy

Category C: Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

Sulfadoxine + Pyrimethamine and Lactation

Contraindicated in lactation

Sulfadoxine + Pyrimethamine and Children

Should not be given to infants younger than 2 months of age because of inadequate development of glucuronide-forming enzyme system.

Sulfadoxine + Pyrimethamine and Geriatic

Use with caution because of the greater frequency of decreased hepatic, renal, or cardiac function, and concomitant diseases or other drug therapy.

Sulfadoxine + Pyrimethamine and Other Contraindications

Severe renal or hepatic impairment, blood dyscrasias, hypersensitivity to components, megaloblastic anaemia due to folate deficiency, pregnancy at term and during lactation, infants ≤ 2 months old.

Storage

Information Not Available

Lab interference

Information Not Available

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