I am 19 weeks pregnant and took one benadryl (diphenhydramine) tablet for sinus infection. about 2 hours later i almost had two anxiety attacks along rapid heartbeat?

Unusual: Benadryl (diphenhydramine) usually causes drowsiness but may rarely cause a stimulant effect especially in very young children. It may also induce rapid heart beats due to its anticholinergic effect which is not found in newer generation antihistamine. However, these two events may be unrelated if you had taken Benadryl (diphenhydramine) before without problem. Benadryl (diphenhydramine) does nothing for sinus infection . See doc if lasting>10 days.