Pyrimethamine
Pyrimethamine is oral antimalarial agent. Pyrimethamine is a folic acid antagonist and dihydrofolate reductase inhibitor. Pyrimethamine is 2,4-diaminopyrimidine related to trimethoprim.
Primary Characteristics
It is of Synthetic origin and belongs to Pyrimidine.
It belongs to Dihydrofolate reductase inhibitor pharmacological group on the basis of mechanism of action and also classified in Antimalarial Agent pharmacological group.
Molecular Weight: 248.7 · pKa: 7.3 · Solubility in Water: practically Insoluble · Solubility in Alcohol: 1 in 200 · Non-proprietary name: Pyrimethamine.
Pharmacokinetics
Absorption: Pyrimethamine has an oral bioavailability is 60.5% (±9.5%).
Distribution: Pyrimethamine has a volume of distribution is 2.9 l/kg. plasma protein binding is 87 %.
Elimination: plasma half-life is 35 - 175 hr.
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Indications
Pyrimethamine is primarily indicated in conditions like Malaria, Malaria prophylaxis, Malaria treatment, Protozoa infection, Toxoplasmosis.
Contraindications
Pyrimethamine is contraindicated in conditions like Anaemia.
Dosage
Pyrimethamine's dosage details are as follows:
| Dose | Single Dose | Frequency | Route | Instructions |
|---|---|---|---|---|
| Adult Dosage | ||||
| 25 mg | 25 mg | — | PO | Once in a Week |
| Paediatric Dosage (20kg) | ||||
| 0.5 mg/kg | 0.5 mg/kg | Every 24h | Oral | Double dose for 1st 3 days |
| Neonatal Dosage (3kg) | ||||
| No data. | ||||
Drug Interactions
Always consult your physician for the change of dose regimen or an alternative drug of choice that may strictly be required.
Side Effects
Pyrimethamine in overdosage may give rise to further complications which include Megaloblastic anemia.
Pyrimethamine produces potentially life-threatening effects which include Agranulocytosis, Disseminated intravascular coagulation. Careful monitoring is needed with proper medical management.
The signs and symptoms that are produced after acute overdosage of Pyrimethamine are Deafness , Fever, Coma, Dyspnea, Tachycardia , Blindness.
Pyrimethamine is known to cause more or less tolerable side effects which are usually transient. These include Photosensitivity reactions, Rashes .
Warnings / Precautions
Interference in Pathology
Pyrimethamine may interfere in the diagnosis of Complete blood cell count.
Available Brands
Storage Conditions
Drug Classification
- 1.6.4.3 — Antimalarials
- 2.6.4.5 — Antipneumocystosis and antitoxoplasmosis drugs
Manufacturers
Manufacturers of Pyrimethamine in Pakistan: