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Healthcare Communications

Fexofenadine

 

Allergy

* Altered reaction of body to antigenic (allergen) stimulus

* Type 1 (Anaphylactic) reaction associated with:
- High IgE levels
- Attachment of IgE to mast Cells
- Antigen reacts with IgE at mast cells to release allergic mediators, e.g., histamine

 

Important Allergic Conditions

* Allergic Rhinitis
- Seasonal
- Perennial
* Urticaria

 

Fexofenadine

* Carboxylic acid metabolite of terfenadine
* Selective histamine H1 blocker
* Zwitterion, with both positive and negative charge
* Poor lipid solublity, does not cross blood-brain barrier
* Non sedating
* Free from cardiac arrhythmias associated with terfenadine

 

Actions

* Selectively blocks histamine H1 receptors
* Prevents effects of histamine on H1 receptors, i.e., prevents nasal mucosal inflammation in allergic rhinitis, and skin inflammation in urticaria
* Checks associated manifestations i.e., sneezing and rhinorrhoea in allergic rhinitis, and redness and itching in urticaria
* Suitable for prevention of allergic attacks

 

Pharmacokinetics

* Well absorbed by from GI tract
* No metabolism in the liver, hence
- unlikely to interact with other drugs metabolised in the liver
- safe in liver impairment
* Peak levels in 1-3 hours
* Excreted in stools and urine
* Pharmacokinetics in elderly, and patients with cardiac and renal disease are similar to healthy subjects
* Plasma levels, half-life are in acceptable range in patients with renal disease

 

Indications

* Allergic rhinitis
* Urticaria

 

Contraindications

* Hypersensitivity to fexofenadine, terfenadine

 

Precautions

* Safety in children below 12 years not established
* Carcinogenicity / mutagenicity / impairment of fertility as for terfenadine
* No genotoxic activity
* Safety in pregnancy and lactation not established

 

Drug Interactions

* Erythromycin or ketoconazole produce a 2 - 3 times increase in the plasma levels of fexofenadine. This is not accompanied by QT changes in the ECG or increase in adverse effects compared to the drugs given alone
* Antacids reduce bioavailablitity of fexofenadine

 

Adverse Reactions

* Generally well tolerated
* Headache, dyspepsia, fatigue, drowsiness and nausea have been reported

 

Dosage & Administration

* 60mg twice daily, or
* 120mg once daily, or
* 180mg once daily, when required
* No dosage adjustment necessary in elderly or in patients with hepatic or renal impairment