Fexofenadine
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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
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Important
Allergic Conditions
* Allergic
Rhinitis
- Seasonal
- Perennial
*
Urticaria
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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
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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
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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
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Indications
* Allergic
rhinitis
* Urticaria
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Contraindications
* Hypersensitivity
to fexofenadine, terfenadine
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Precautions
* Safety in
children below 12 years not established
* Carcinogenicity / mutagenicity / impairment offertility as for
terfenadine
* No genotoxic activity
* Safety in pregnancy and lactation not established
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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
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Adverse
Reactions
* Generally
well tolerated
* Headache, dyspepsia, fatigue, drowsiness and nausea have been reported
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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
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