Opiates suppress the central nervous system. The cramps and diarrhea are one of the results of a rebound effect where previously unstimulated reflexes become hyperactive when the depressant is removed.

The correct spelling is "withdrawal."

The past tense of suppress is suppressed.

Lisa had to suppress her anger with her younger brother for spilling her milk because she knew he didn't do it on purpose.

The class was unable to suppress their laughter as the chalk blew into the teacher's face.

The government called in troops to suppress the demonstrations in the city.

Suppress has two syllables. Sup-press.