Generic
Terfenadine
1 brands available in the market
At a glance
Terfenadine is an antihistamine used for allergic conditions. It relieves itching, swelling, and rashes by blocking histamine effects. Its use has been banned due to serious side effects.
Description
Terfenadine is a piperidine derivative non-sedating H1 receptor antagonist antihistamine. It competitively binds to histamine receptors, blocking the effects of allergy mediators. However, due to the risk of QT prolongation and Torsade de pointes, its use has been banned in many countries.
Indications
- Allergic conditions
Therapeutic class
Antihistamines
Pharmacological class
H1 Receptor Antagonist
Pharmacology
Terfenadine is a non-sedating antihistamine that blocks peripheral H1 receptors to prevent histamine-induced allergic reactions. However, due to CYP3A4 metabolism, it has significant drug interaction and QT prolongation risks.
Mechanism of action
Relieves allergy symptoms by blocking H1 receptors.
Dosage
Adult Dose (Oral):
- 60-120 mg/day in the morning or 60 mg twice daily
- Maximum: 120 mg/day
Pediatric Dose (>12 years, >50 kg):
- 60-120 mg/day in the morning or 60 mg twice daily
- Maximum: 120 mg/day
Administration
- Take with or without food
- Swallow tablet whole; do not chew, crush, or break
- Take at the same time each day
Missed dose
If you miss a dose, take it as soon as you remember; if almost time for the next dose, skip it; do not double the dose.
Side effects
Common Side Effects:
- Diarrhea, headache
- Elevated liver enzymes
- Joint pain, muscle pain
- Loss of appetite, nausea
- Rash, abdominal pain
Serious (Rare):
- QT interval prolongation
- Torsade de pointes (fatal arrhythmia)
Precautions & warnings
- Banned in many countries due to serious side effects
- Stop use 3 days before allergy testing
- Caution in liver disease
- Caution in pregnancy and lactation
Contraindications
- Porphyria
Drug interactions
- CYP3A4 inhibitors (ketoconazole, itraconazole, erythromycin): Increase terfenadine levels and QT prolongation risk (potentially fatal)
Food interactions
Alcohol is unsafe with Terfenadine (excessive drowsiness).
Use in pregnancy
Use in Pregnancy: May be unsafe; animal studies show harmful effects; consult your doctor.
Pregnancy Category: C — always consult a doctor before taking during pregnancy.
Use in lactation
Use in Lactation: Caution required; hold breastfeeding until treatment is completed; consult your doctor.
Pediatric use
Indicated for children >12 years, >50 kg
Geriatric use
Caution required in elderly patients
Renal / hepatic impairment
Renal Impairment: Limited information; consult your doctor.
Hepatic Impairment: Limited information; consult your doctor.
Overdose effects
Overdose may cause QT prolongation and arrhythmia risk; provide symptomatic treatment.
Storage conditions
Store in a cool and dry place, protected from light; keep out of reach of children.
Chemical structure
Terfenadine