calfin 25mg/500mg tablet - Pyrimethamine (25mg) + Sulfamethoxazole (500mg) medicine

calfin 25mg/500mg tablet - Uses, Price, Side Effects & Substitutes

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๐Ÿญ Redson Laboratories Pvt Ltd ๐Ÿ“ฆ Varies by brand ๐Ÿ’Š Allopathy ๐Ÿ“… Updated: Jul 1, 2026
๐Ÿ“‹ Prescription Required ๐Ÿ’Š Generic Available
Medically Reviewed
SaathiMed Expert Panel | Jul 01, 2026

What is calfin 25mg/500mg tablet used for?

Calfin (Pyrimethamine + Sulfamethoxazole) is used to treat ANTI MALARIALS. It contains Pyrimethamine (25mg) + Sulfamethoxazole (500mg), which Pyrimethamine inhibits dihydrofolate reductase; Sulfamethoxazole inhibits dihydr. Always consult your doctor before use. Take as prescribed.

  • Generic Name: Pyrimethamine + Sulfamethoxazole
  • Manufacturer: Redson Laboratories Pvt Ltd
  • Form: Allopathy
  • Pregnancy Category: C
  • Prescription Required: Yes
๐Ÿ’ก Did You Know? Over 80% of the antiretroviral drugs used globally to combat AIDS are supplied by Indian pharmaceutical companies.

๐Ÿ’Š calfin 25mg/500mg tablet Uses & Benefits

Treatment of chloroquine-resistant falciparum malaria; toxoplasmosis (in combination with other agents).

Off-label uses: Treatment of Pneumocystis jirovecii pneumonia (PCP) in combination with other agents.

๐Ÿ“‹ Drug Information

Generic Name(s)Pyrimethamine + Sulfamethoxazole
Brand NameCalfin
ManufacturerRedson Laboratories Pvt Ltd
Packaging / FormVaries by brand (Allopathy)
Therapeutic ClassANTI MALARIALS
Action ClassAntimalarial combination
Route of AdministrationOral
StorageStore at 20-25ยฐC (68-77ยฐF), protect from light and moisture.
Shelf LifeAs per manufacturer

๐Ÿ”ฌ Pharmacology (PK/PD)

Pharmacokinetics

AbsorptionWell absorbed orally
DistributionDistributed widely; crosses placenta and enters breast milk
Protein BindingPyrimethamine: 87%; Sulfamethoxazole: 70%
MetabolismPyrimethamine: hepatic; Sulfamethoxazole: hepatic (acetylation)
Half-LifePyrimethamine: 80-95 hours; Sulfamethoxazole: 10-12 hours
ExcretionRenal (both)
Bioavailability>90% for both
Onset of Action1-2 hours
Peak Plasma TimePyrimethamine: 2-6 hours; Sulfamethoxazole: 1-4 hours
Duration of ActionApproximately 7 days

How It Works

Pyrimethamine inhibits dihydrofolate reductase; Sulfamethoxazole inhibits dihydropteroate synthase, sequentially blocking folate synthesis in Plasmodium.

Mechanism Steps

1Pyrimethamine binds to dihydrofolate reductase (DHFR) in Plasmodium, inhibiting conversion of dihydrofolate to tetrahydrofolate.
2Sulfamethoxazole competitively inhibits dihydropteroate synthase (DHPS), blocking incorporation of para-aminobenzoic acid (PABA) into dihydropteroate.
3Sequential blockade of folate synthesis leads to depletion of tetrahydrofolate, essential for DNA synthesis and cell division.

๐Ÿ’ก How to Take calfin 25mg/500mg tablet

Follow your doctor's prescription exactly.

โš ๏ธ Side Effects of calfin 25mg/500mg tablet

โœ… Common Side Effects

  • Nausea
  • Vomiting
  • Diarrhea
  • Rash
  • Headache

๐Ÿšจ Serious Side Effects

  • Stevens-Johnson syndrome
  • Toxic epidermal necrolysis
  • Agranulocytosis
  • Aplastic anemia
  • Hepatotoxicity

โš ๏ธ Rare Side Effects

  • Megaloblastic anemia
  • Pancreatitis
  • Interstitial nephritis
  • Photosensitivity

Consult your doctor if you experience any unusual symptoms.

๐Ÿ”ฌ Drug Interactions

โš ๏ธ DrugSeverityEffect
Warfarin Major Increased bleeding risk
Methotrexate Major Increased methotrexate toxicity
Phenytoin Major Increased phenytoin levels
Sulfonylureas Major Increased hypoglycemic effect
Oral contraceptives Moderate Reduced contraceptive efficacy
Cyclosporine Moderate Increased nephrotoxicity
Digoxin Moderate Increased digoxin levels
Antacids Minor Reduced absorption
Vitamin K Minor Antagonizes anticoagulant effect

๐Ÿšจ Major Interactions

  • Warfarin
  • Methotrexate
  • Phenytoin
  • Sulfonylureas

โšก Moderate Interactions

  • Oral contraceptives
  • Cyclosporine
  • Digoxin

โ„น๏ธ Minor Interactions

  • Antacids
  • Vitamin K

๐Ÿฝ๏ธ Food Interactions

No significant food interactions.

๐Ÿท Alcohol Interaction

Avoid alcohol due to increased hepatotoxicity risk.

๐Ÿ›ก๏ธ Safety & Warnings

๐Ÿšซ Contraindications

Hypersensitivity to sulfonamides or pyrimethamine; severe hepatic or renal impairment; megaloblastic anemia; pregnancy (especially first trimester); lactation; infants <2 months.

๐Ÿ“Š Monitoring Parameters

CBC, renal and hepatic function, folate levels, signs of hypersensitivity.

๐Ÿคฑ Lactation Safety

Contraindicated (excreted in milk, risk of kernicterus in infants)

๐Ÿ’Š Overdose Management

Gastric lavage, supportive care, folinic acid (leucovorin) to counteract folate deficiency.

โฐ Missed Dose

Take as soon as remembered; if near next dose, skip missed dose. Do not double dose.

๐Ÿ‘จโ€โš•๏ธ Reviewed by Expert

SaathiMed Expert Panel

MD, PhD - Pharmacology

Reviewed: Jul 01, 2026

๐Ÿ”— View Profile

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