Fexofenadine - What Is It?

Fexofenadine is an antihistamine drug which is used in the treating of allergy symptoms. When the antihistamine terfenadine had potentially serious contraindications, fexofenadine was developed as its successor. Fexofenadine does not readily cross the blood-brain barrier, causing less drowsiness than first generation histamine receptor antagonists. Fexofenadine is an H1 receptor antagonist. Fexofenadine is indicated for relief of symptoms associated with seasonal allergic rhinitis and treatment of chronic idiopathic urticaria.

A History

In studies, terfenadine, the older antihistiminic agent of the two, was found to metabolize into fexofenadine, a related carboxylic acid. Fexofenadine retained all of the biological activity of terfenadine while giving patients fewer negative side effects, hence the replacing of terfenadine by fexofenadine in the market. In 1993, fexofenadine was synthesized by Sepracor, a Massachusetts-based biotechnology company, which then sold the development rights to Hoechst Marion Roussel, now part of Sanofi-Aventis. Fexofenadine was later approved by the FDA in 1996.

Dosage

For children from 6 months to less than 2 years old who suffer from chronic idiopathic urticaria, the recommended dosage is 15 mg twice daily. For sufferers of seasonal allergic rhinitis, the recommended dosage is 30 mg twice daily for children 2-11 years old, 60 mg twice daily or 180 mg once daily for adults or children over 12 years old, and 60 mg once daily for elderly patients (adjust for renal impairment.) Administer with water only and not with fruit juices. This medication should be taken exactly as it was prescribed. The medication should not be taken in larger amounts, or taken for longer than recommended by a doctor. The tablet form should be taken with a full glass of water. No other type of liquid should be used. The oral suspension form should be shaken well immediately before a dose is measured. To be sure the correct dose is taken, the liquid should be measured with a marked measuring spoon or medicine cup, not with a regular table spoon. If no dose-measuring device is available, one should be obtained from the pharmacist.

The disintegrating tablet form should be taken on an empty stomach, at least 1 hour before a meal or 2 hours afterwards. A doctor should be informed if symptoms do not improve,or if they get worse after you start taking fexofenadine. Never take more fexofenadine than the doctor has prescribed.

If a dose is missed, the missed dose should be taken as soon as possible. If a dose is missed and it is almost time for the next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Never take extra medicine to make up for the missed dose.

Common dosage forms are 6 mg/mL (30 mL, 300 mL) in suspension form. In tablet form, the dosages are 30 mg, 60 mg, and 180 mg. Fexofenadine should be stored at room temperature and away from moisture and heat. The medicine bottle should be kept tightly closed.

Side Effects

Common side effects include vomiting, nausea, weakness, dizziness, fatigue, drowsiness, unusual bowel movements, diarrhea, and headache. When taken with fluoxetine, this drug may cause drowsiness.

Due to their infrequency, reports of the effects of a fexofenadine overdose are not well established. In tests on mice, no deaths occurred at 5000 mg/kg, which is 110 times the maximum recommended dose for an adult human. Further research shows no deaths in rats at the same concentration, which is equal to 400 times the recommended dose for an adult human. Research on humans ranges from a single 800 mg dose, to a 690 mg dose twice daily for a month, with no significant negative side effects in comparison to a placebo. If an overdose does occur, seek emergency medical attention. Overdose symptoms may include dry mouth, dizziness, or drowsiness.