A 44-year-old member asked:
How much time after you take cough medicine do you feel the sleepy side effects?
1 doctor answer • 1 doctor weighed in
Emergency Medicine 24 years experience
About 1-3 hrs: Most night time cold meds contain an antihistamine that helps you fall asleep. Diphenhydramine and Doxylamine are the common drugs used and their onset of action is from 1-3 hours and 2-3 hrs respectively. Most other antihistamines would have a similar onset of action.
3.9k viewsAnswered >2 years ago
Last updated Oct 29, 2015
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