Methapyrilene hydrochloride is an uncommon antihistamine found in cold or flu medicines. Methapryrilene hydrochloride overdose occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication.
Methapyrilene hydrochloride is found in older antihistamine medications. It was removed from the market in 1979 because it was found to contribute to cancer after long-term use.