Terfenadine

Drug #702

Terfenadine is a H1-antagonist antihistamine that is similar in structure to astemizole. it, however, has a much shorter duration of action. Unlike other H1-antagonists, therapeutic doses of it produce insignificant anticholinergic activity or sedation, perhaps due to poor penetration of the drug into the CNS. it blocks the effects of histamine on H1-receptors in the GI tract, uterus, large blood vessels, and bronchial muscle. Blockade of H1-receptors also suppresses the formation of edema, flare, and pruritus that result from histaminic activity. At higher concentrations, H1-receptor antagonism becomes relatively irreversible. Terfenadine is used to provide relief from symptoms of allergies such as rash, hives, watery eyes, runny nose, itching eyes and sneezing, also used in skin allergies such as urticaria.

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Primary Characteristics

It is of Synthetic origin and belongs to Butyrophenones.

It belongs to H1-antagonist pharmacological group on the basis of mechanism of action.

Molecular Weight: 471.7 · pK_a: 8.58 · Solubility in Water: Insoluble · Solubility in Alcohol: 1 in 59 · Non-proprietary name: Terfenadine.

Pharmacokinetics

Absorption: Terfenadine has an oral bioavailability is 100%, pre-systemic (first-pass) metabolism accounts for 99%.

Distribution: Terfenadine has a plasma protein binding is 70 %.

Elimination: it is metabolised via Hepatic, plasma half-life is 16 - 23 hr.

Indications

Terfenadine is primarily indicated in conditions like Advanced ovarian cancer, Allergy, Angioedema, Angiooedema, Asthma, Conjuctivitis, Dermatitis, Lung cancer, Rhinitis, Urticaria.

Contraindications

None recorded.

Dosage

Terfenadine's dosage details are as follows:

Dose	Single Dose	Frequency	Route	Instructions
Adult Dosage
1.29 mg/kg	1.29 mg/kg	Every 12h	PO	-
Paediatric Dosage (20kg)
1.2 mg/kg	1.2 mg/kg	Every 12h	Oral	Recommended for 5-12 Yrs. Children
Neonatal Dosage (3kg)
No data.

Drug Interactions

Unknown21 interactions

5 interactions

Major10 interactions

Moderate3 interactions

Always consult your physician for the change of dose regimen or an alternative drug of choice that may strictly be required.

Side Effects

Terfenadine in overdosage may give rise to further complications which include Allergic hepatitis .

The signs and symptoms that are produced after acute overdosage of Terfenadine are Convulsions , Ventricular arrhythmias.

Terfenadine is known to cause more or less tolerable side effects which are usually transient. These include Alopecia, Angioedema, Burning, Depression, Desquamation , Drowsiness, Fatigue, Photosensitivity.

Warnings / Precautions

Terfenadine should be used with caution in bone marrow depression. Patients should observe caution while driving or performing other task requiring alertness because it may cause drowsiness. It should be used with caution in patients with urinary retention, history of bronchial asthma, hyperthyroidism, cardiovascular or liver disease. It should be used with caution in person with acute or chronic respiratory impairment, especially in children. Do not administer S/C because irritation or lesion may occur.

Available Brands

None recorded.

Storage Conditions

Terfenadine should be stored Tab.

Drug Classification

1.3 — Anti-allergics (Antihistamines) and drugs used in anaphylaxis