by Dr. Manura Nanayakkara

Created on: June 29, 2010   Last Updated: June 30, 2010

Fexofenadine is a newer non-drowsy antihistamine. It is a metabolite of relatively toxic antihistamineTerfenadine. This medication is useful in the treatment of allergic rhinitis and chronic idiopathic urticaria. Common brands are Allergra® and Telfast®.

This is a especially useful medication in the spring season due to increased presence of allergens in the environment. Allergic rhinitis is a common disease doctor’s treat in this spring season. Chronic idiopathic urticaria is a disease with hives without an identifiable cause.

Although Fexofenadine is a metabolite of Terfenadine, Toxic potentials are not shared. This medication acts on the Histamine 1 receptors and block them. This medication does not cross the blood brain barrier. So less drowsiness is experienced by the patient.

 Before starting this drug, you must tell the doctor whether you have any kidney disease, or liver disease. If you are taking over the counter medications or recreational drugs, you should inform that to your doctor as well. The doctor should also know whether you are pregnant or nursing. It is equally important to inform your doctor if you are planning to get pregnant.

This drug can be taken without regard to meals. This drug is usually not given with anti-acid medications such as Aluminum Hydroxide and Magnesium Hydroxide. This medication should be taken as a whole with full glass of water. Breaking or crushing the tablets may leads to reduced effectiveness as well as increased side effects.

This medication is available as tablets, extended release tablets and tablets with mixed combination of Pseudoephedrine. Usual dose in allergic rhinitis is 180mg daily for adults and 30mg two times a day for children. Doctor will reduce the dose in renal and liver problems.

Side effects

Most of the side effects are due to the Pseudoephidrine that is present in some combinations. They are reduced sleep, dry mouth, dizziness, anxiety and palpitations.  Drowsiness is one of the commonest side effects. Headache is another common side effect. Nausea and vomiting are other common side effects.

Drug interactions

This drug inhibits the hepatic microsomal enzyme system. This leads to accumulation of certain drugs that are metabolized in above system. Taking Drugs such as Erythromycin and Ketoconazole leads to increased levels of Fexofenadine. Patients should not take MAO inhibitors while on Fexofenadine with Pseudoephedrine. Grapefruit juice can decrease the blood level of Fexofenadine.

Pregnancy

Even though no evidence of fetal harm is demonstrated, this drug should be used cautiously especially in first three months of the pregnancy.

Breast feeding

This medication is found to have significant amounts in breast milk.  So manufacturer as well as doctors are advised not to use this medication in nursing mothers.

 Sources

British National Formulary

AHFS Drug Information

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