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Dr. Mark
Dr. Mark, Doctor (MD)
Category: Health
Satisfied Customers: 11946
Experience:  U.S. Physician/Surgeon in Neurosurgery
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I have epilepsy. I know that certain antihistamines cross ...

Resolved Question:

I have epilepsy. I know that certain antihistamines cross the blood brain barrier and reduce my seizure threshold. I am having terrible allergy problems, however, and cannot get into my doctor for a prescription of Allegra until the 20th. My epilepsy is well controlled. How risky is it for me to take some Zyrtec?
Submitted: 8 years ago.
Category: Health
Expert:  Dr. Mark replied 8 years ago.

Certain antihistamines (the "first generation") are thought to cross the brain blood barrier and lower seizure threshold.

Zyrtec, Allegra, and Claritin are part of the second generation and it does not appear that these drugs have been implicated in lowering the seizure threshold. A study in rats found that Zyrtec, even in large doses did not produce EEG changes/seizures in rats that were predisposed to seizures.

Allegra, because it is the least likely to cross the blood brain barrier is often prescribed, but according to the medical literature out there, the Zyrtec does not appear to confer a signficant risk of seizures -- of course, there are no guarantees in anything, and such questions are best discussed with your doctor who knows your medical history best.
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