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Dermatologists prescribing any of the medications off label for pruritic dermatosis will find the dosages recommended are too low to suppress the itch of the dermatitic process.
"In the past we have used first-generation antihistamines, such as hydroxyzine, diphenhydramine, etc., but they are all quite sedating. The sedation rate for hydroxyzine alone can be up to 40 percent, depending on the age of the patient and the doses of medication given," says Joseph Bikowski, M.D., clinical assistant professor, division of dermatology, Ohio State University, Columbus, Ohio.
Dr. Bikowski, who also practices dermatology in Sewickley, Pa., says that in the last decade second-generation antihistamines fexofenadine, loratadine, metabolic product desloratadine and cetirizine have come to the rescue, offering good control of itching with far less sedation.
"Scientists have been able to metabolize these ... to their second-generation stage, and in the process of doing that, have been able to decrease the sedation rate," he says.
"For example, fexofenadine has a sedation rate equal to placebo, which is 1.9 percent. Loratadine has a sedation rate of about 6.9 percent and cetirizine has a sedation rate of about 13.7 percent."
All three medications are indicated for treatment of either seasonal allergic rhinitis or chronic idiopathic urticaria.
Dermatologists prescribing any of the medications off label for pruritic dermatosis will find the dosages recommended are too low to suppress the itch of the dermatitic process, according to Dr. Bikowski.
Turning up the heat
"However, if you double, triple or quadruple the package insert dosages, then you can suppress itch quite effectively," he says.
The package inserts of each of the medications indicate that doubling, tripling or quadrupling the dosages is safe. In the case of cetirizine, even increasing the dose recommended on the package insert by six times does not cause adverse events, according to Dr. Bikowski.
"It is safe to do. I have treated pruritic dermatosis with these second-generation antihistamines for the last seven or eight years," he says.
"Whenever I treat pruritic dermatoses and I need an antipruritic systemically, I will use fexofenadine at two 60 mg tablets twice a day, up to two four times a day; loratadine at 10 mg twice a day, up to 10 mg two times, twice a day; or cetirizine at 10 mg twice a day, up to six times a day."
Of all the three, fexofenadine is the least sedating because it is a zwitterion, an electronically neutral chemical compound, which does not readily enter the brain from the blood to cause sedation.
Dr. Bikowski starts patients at one of the three medication's lowest off-label indications, which is twice package insert. He chooses which medication to use based on several variables, including which is most likely to be covered by the patient's insurance, how much the patient insists on nonsedation and whether a patient is willing to use over-the-counter or prescription medication.
He says he does not combine antihistamines, but rather aims to stop itch without sedation.
"If the patient is having difficulty sleeping because of the itch, I do not give the patient a sedating antihistamine to put them to sleep at night. I up my dosages of the nonsedating antihistamine to suppress the itch, so they go to sleep because they are not itching," he tells Dermatology Times.