CIndU Antihistamines: Why Second-Generation H1 Therapy Falls Short for Many

"CIndU Antihistamines: Why Second-Generation H1 Therapy Falls Short for Many" takes up the question of what standard antihistamine therapy can and cannot deliver.

Dr. Dasilva asks for Dr. Finklea's experience and opinions on first- and second-generation antihistamines in CIndU. Dr. Finklea explains that first-generation antihistamines are no longer part of the international expert consensus guidelines because they cause sedation and carry anticholinergic effects, so they should be avoided altogether. Second-generation H1 antihistamines are first-line therapy. They are usually well tolerated and inexpensive at standard once-daily dosing. However, they are effective only about 20% to 50% of the time, which means 50% to 80% of patients remain inadequately controlled. Even when clinicians up-titrate to four times the standard dose, only about 22% to 72% of patients respond, depending on the CIndU subtype. At those higher doses, dry mouth and dry eye begin to appear, and some sedation develops as the drugs start to cross the blood-brain barrier. Dr. Finklea identifies this as the heart of the treatment gap. Most patients are not controlled on antihistamines alone, despite the tolerability and low cost that make them the natural starting point.

Dr. Dasilva agrees and points out that antihistamines are familiar to patients because they are available over the counter. He cautions that easy access does not mean patients tolerate them well, since side effects can still be bothersome. He adds that colleagues, including allergists, hold differing opinions about which agent is most effective or least sedating. Opinions also differ on which is least likely to cross the blood-brain barrier, though in his view all of them can. Dr. Finklea responds that fexofenadine is the only one she believes never crosses the blood-brain barrier, while the others become sedating as the dose rises.

Our next episode, "CIndU Treatment Algorithm: Antihistamine Up-Titration and Unmet Needs," turns to how Dr. Finklea selects and up-titrates an antihistamine in practice and what comes after it.