Promethazine syrup effect?

Multiple effects. Promethazine is a potent antihistamine that can cause dizziness, drowsiness, dry mouth, nausea, vomiting, weakness and occasionally more serious central nervous system side effects. It is usually well tolerated in most people.

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Promethazine/codeine syrup side effect?

Usually None! In normal dossage, the only remote side-effect would be constipation, maybe itching although rare. With overdose or with blunts or cigs dipped and smoked, hallucinogenic. Read more...
Well tolerated. There are usually few side effects except maybe a little sedation. Read more...