Terfenadin AL

Terfenadin AL Uses, Dosage, Side Effects, Food Interaction and all others data.

Terfenadin AL competes with histamine for binding at H1-receptor sites in the GI tract, uterus, large blood vessels, and bronchial muscle. This reversible binding of terfenadine to H1-receptors suppresses the formation of edema, flare, and pruritus resulting from histaminic activity. As the drug does not readily cross the blood-brain barrier, CNS depression is minimal.

Terfenadin AL, an H1-receptor antagonist antihistamine, is similar in structure to astemizole and haloperidol, a butyrophenone antipsychotic. The active metabolite of terfenadine is fexofenadine.

Trade Name Terfenadin AL
Availability Discontinued
Generic Terfenadine
Terfenadine Other Names Terfenadin, Terfenadina, Terfénadine, Terfenadine, Terfenadinum
Related Drugs hydroxyzine, loratadine, levocetirizine, Vistaril, Atarax, Xyzal
Type
Formula C32H41NO2
Weight Average: 471.6734
Monoisotopic: 471.313729561
Protein binding

70%

Groups Approved, Withdrawn
Therapeutic Class Non-sedating antihistamines
Manufacturer
Available Country
Last Updated: September 19, 2023 at 7:00 am
Terfenadin AL
Terfenadin AL

Uses

Terfenadin AL is used for the treatment of allergic rhinitis, hay fever, and allergic skin disorders

Terfenadin AL is an antihistamine. Antihistamines prevent sneezing, runny nose, itching and watering of the eyes, and other allergic symptoms. This is used to treat allergies, hives (urticaria), and other allergic inflammatory conditions. Terfenadin AL may also be used for purposes other than those listed in this medication guide.

Terfenadin AL is also used to associated treatment for these conditions: Allergic Rhinitis (AR), Allergies, Allergy Skin, Pollen Allergy

How Terfenadin AL works

Terfenadin AL competes with histamine for binding at H1-receptor sites in the GI tract, uterus, large blood vessels, and bronchial muscle. This reversible binding of terfenadine to H1-receptors suppresses the formation of edema, flare, and pruritus resulting from histaminic activity. As the drug does not readily cross the blood-brain barrier, CNS depression is minimal.

Dosage

Terfenadin AL dosage

Adult (>12 year and >50 kg): 60-120 mg in the morning or 60 mg bid. Max: 120 mg daily.

Renal Impairment: CrCl <40: Half the usual daily dose

Side Effects

Anxiety, palpitations, insomnia, mild GI distubances, erythema multiforme and galactorrhoea.

Toxicity

Mild (e.g., headache, nausea, confusion), but adverse cardiac events including cardiac arrest, ventricular arrhythmias including torsades de pointes and QT prolongation have been reported. LD50=mg/kg (orally in mice)

Precaution

Child and elderly. Avoid in patients with cardiac or significant hepatic disease, electrolyte imbalance, or known or suspected prolongation of the QT interval. Lactation, pregnancy.

Interaction

Increased risk of ventricular arrhythmia with triazole and imidazole antifungals, macrolide antibacterials, streptogramin antibacterials, SSRI, HIV-protease inhibitors and non-nucleoside reverse transcriptase inhibitors, arrhythmogenic drugs, diuretics, astemizole and zileutron.

Food Interaction

  • Exercise caution with grapefruit products. Grapefruit is a CYP3A4 inhibitor, and terfenadine is metabolized by CYP3A4. Co-administration may increase terfenadine concentrations and the risk of QT prolongation.
  • Exercise caution with St. John's Wort. This herb induces CYP3A4 and terfenadine is a substrate of CYP3A4.

[Major] CONTRAINDICATED: The consumption of grapefruit juice has been associated with significantly increased plasma concentrations of terfenadine.

The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits.

Terfenadin AL in high serum levels has been associated with prolongation of the QT interval and development of torsade de pointes, a potentially fatal ventricular arrhythmia.



MANAGEMENT: Due to the risk of cardiotoxicity, patients receiving the drug should be advised to avoid consumption of grapefruit products.

Loratadine, cetirizine, and fexofenadine may be safer alternatives in patients who may have trouble adhering to the dietary restriction.

Elimination Route

On the basis of a mass balance study using 14C labeled terfenadine the oral absorption of terfenadine was estimated to be at least 70%

Half Life

3.5 hours

Pregnancy & Breastfeeding use

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.

Contraindication

Porphyria.

Innovators Monograph

You find simplified version here Terfenadin AL

FAQ

What is Terfenadin AL used for?

Terfenadin AL is used to treat allergies, hives (urticaria), and other allergic inflammatory conditions.

What is the action of Terfenadin AL?

Terfenadin AL is an antihistamine. Antihistamines prevent sneezing, runny nose, itching and watering of the eyes, and other allergic symptoms.

What are the common side effects of Terfenadin AL?

The common side effects of Terfenadin AL are include: dizziness, syncopal episodes, palpitations, ventricular arrhythmias (including torsades de pointes), cardiac arrest, and cardiac death.

Is Terfenadin AL safe during pregnancy?

Terfenadin AL should only be given during pregnancy when there are no alternatives and benefit outweighs the risk.Terfenadin AL has been assigned to pregnancy category C. Animal studies have failed to reveal evidence of teratogenicity. There are no controlled data in human pregnancy.

Is Terfenadin AL safe during breastfeeding?

Terfenadin AL may be preferred in breastfeeding over other antihistamines that do cause sleepiness. Information from Terfenadin AL, which breaks down into Terfenadin AL in the body, suggests that the amount of Terfenadin AL in the breast milk is small.

Can I drink alcohol with Terfenadin AL?

Alcohol may increase drowsiness and dizziness while you are taking Terfenadin AL.

Can I overdose on Terfenadin AL?

Consider administration of 60 mg of Terfenadin AL twice daily. Do not over dose Terfenadin AL. It can cause serious cardiovascular events.

What is the Interactions of Terfenadin AL?

Do not consume alcohol while taking Terfenadin AL. Alcohol can increase the symptoms of dizziness. Do not take caffeine or diet pills while taking Terfenadin AL.

Can Terfenadin AL cause dizziness?

Terfenadin AL may cause dizziness or drowsiness. If you experience dizziness or drowsiness, avoid these activities.

Why was Terfenadin AL removed from the market?

Terfenadin AL was taken off the market due to the risk of cardiac arrhythmia caused by QT prolongation. The active metabolite is not cardiotoxic, however, and is now sold under the Terfenadin AL name Allegra.

*** Taking medicines without doctor's advice can cause long-term problems.
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