Fexofenadine is a new non-sedating antihistamine. It is the active metabolite of terfenadine which has been withdrawn from the market in some countries. Fexofenadine is a safer alternative with similar efficacy in relieving symptoms associated with seasonal allergic-rhinitis or urticaria.
Seasonal allergic rhinitis or hay fever has a significant impact on a patient’s quality of life, particularly if their sleep is disturbed. Severe symptoms can lead to lost time from work or school or impaired daily activities. A careful history is the most important part of clinical assessment. If symptoms are seasonal, pollen allergy is most likely whereas perennial symptoms suggest an allergy to dust mites, moulds or household pets. Antihistamines (H1-receptor antagonists) provide symptomatic relief (eg. from runny nose, sneezing, itchy/watery eyes). How-ever, they are ineffective for the relief of nasal congestion, in contrast intranasal corticosteroids are effective in this regard.
The newer anthistamines terfenadine, loratadine and astemizole were developed to reduce the side effects of drowsiness and dry mouth seen with the older anthistamines. Hence these newer anthistamines are favoured when such side effects are a significant problem (ie. when alertness and motor coordination are required). When drugs are in wide clinical use, rare but serious adverse events are sometimes detected. Terfenadine has been withdrawn from the market in some countries because of serious and sometimes fatal cardiac rhythm disturbances (ie. torsades de pointes). These were due to high plasma levels resulting from coadministration with ketoconazale and erythromycin or, in some patients, liver disease. Terfenadine is also contraindicated with other drugs such as HIV protease inhibitors, serotonin reuptake inhibitors, zileutin, cisapride and sparfloxacin. Similar contraindications are noted with astemizole.
Fexofenadine is the active acid metabolite. As fexofenadine requires no metabolic transformation, rare cardiac adverse events and other drug interactions should be minimized. Fexofenadine is indicated for the symptomatic relief of seasonal allergic rhinitis and urticaria in adults and children older than 12. If antihistamines are to be taken then they should be used regularly and not sporadically.
Placebo-controlled studies in large groups of patients (n=545 and n=861) with allergic rhinitis have demonstrated the effectiveness of fexofenadine administrated for 2 weeks at twice-daily doses of 60 mg and once-daily doses of 120 or 180 mg.
At the meeting of the American Academy of Allergy, Asthma and Immunology, two placebo-controlled studies were presented demonstrating significant improvement in symptoms and quality of life. Patients with moderate to severe rhinitis received fexofenadine as a twice-daily dose of 60 mg or as a once-daily dose 120 or 18 mg.
When compared with cetirizine in a double-blind trial, once-daily fexofenadine 120 or 180 mg was as effective in controlling rhinitis symptoms. The efficacy of fexofenadine also appears comparable with that of loratadine. Two double-blind studies have been presented showing that loratadine 10 mg once daily worked faster than fexofenadine 60 mg twice daily in 836 patients, and that patients who did not respond to fexofenadine had a better response to loratadine and that loratadine was less likely to fail in the first place.
Fexofenadine is also effective in the relief of symptoms associated with urticaria. A higher dose of 180 or 240 mg once daily for 6 weeks significantly reduced total symptom scores (number of wheals or hives and pruritus). At last year’s American College of Allergy, Asthma and Immunology meeting, three studies were presented supporting the use of fexofenadine 60 mg twice daily in the treatment of patients with chronic idiopathic urticaria.