Early antihistamines had strong sedative effects, causing potentially dangerous daytime sleepiness
Antihistamines have been used to prevent hayfever and treat other allergic reactions for many years. Early antihistamines had strong sedative effects, causing potentially dangerous daytime sleepiness. The drugs’ positive effects are caused by antagonism at the peripheral H1 histamine receptors, and their negative ones by hitting other histamine receptors, notably those in the central nervous system.
Second generation H1 receptor antagonists have improved the safety of these drugs, and a new one from Spain’s Faes with very high selectivity has just been approved in Europe. It is licensed for marketing to Menarini in most European countries in both allergic rhinitis and chronic idiopathic urticaria.
Antihistamine – bilastine
In one dose range clinical trial, the peripheral and central effects of single and repeated oral doses of the drug were studied, in comparison with hydroxyzine and placebo as controls.1 A total of 20 healthy volunteers were given repeated, increasing doses of 20, 40 or 80mg of bilastine, hydroxyzine or placebo on seven consecutive days.
Skin reactivity to an intradermal histamine injection, objective tests of psychomotor performance and subjective mood scales were all evaluated. All active treatments gave a similar and significant reduction in wheal reactions to histamine, and no tolerance or sensitisation was seen with repeat doses. Hydroxyzine gave significantly greater psychomotor impairment than bilastine, and a clear dissociation between peripheral and CNS activity was seen with the new drug.
It has been compared with the existing antihistamine desloratidine in a double blind, randomised, parallel group placebo-controlled trial in patients with symptomatic seasonal allergic rhinitis.2 Doses of 20mg of bilastine significantly reduced the total symptom score compared with placebo, and similar to 5mg doses of desloratidine in its efficacy. Similarly, it was compared with 10mg doses of cetirizine;3 again, it was significantly superior to placebo, and similar to cetirizine.
Trials have also been carried out in chronic idiopathic urticaria.4 It was compared with 5mg doses of levocetirizine and placebo in patients with moderate to severe symptoms. A total of 525 patients were dosed once a day for 28 days in a double blind, placebo-controlled trial, and the new drug gave a significantly greater improvement in symptoms than placebo, and it was similar to levocetirizine.
Its effects on normal day-to-day activities have also been investigated.5 A total of 22 patients were given 20 or 40mg of bilastine, 50mg hydroxyzine or placebo in a randomised, double blind, four-way crossover trial, and given doses once a day for eight days. On days 1 and 8 they performed a driving test, and performance was severely impaired with hydroxyzine, but not at all with bilastine.
1 C. García-Gea et al. J. Clin. Psychopharmacol. 2008, 28, 675
2. C. Bachert et al. Allergy 2009, 64, 158
3. P. Kuna et al. Clin. Exp. Allergy 2009, 39, 1338
4. T. Zuberbier et al. Allergy 2010, 65, 516
5. S. Conen et al. J. Psychopharmacol. 2010 Sep 20. [Epub ahead of print]