Constipation is a possible side effect of drugs taken by the oral route, but it is highly unlikely to occur with the use of
Docusate is a stool-softening laxative that facilitates mixing of oil and water via its surfactant properties. Drugs that have muscarinic blocking effects, like scopolamine and the antihistamines diphenhydramine and promethazine, tend to cause constipation by decreasing GI motility. Loperamide is an opioid derivative, with no analgesic activity, used in the treatment of diarrheal states.
diphenhydramine
docusate
promethazine
loperamide
General Pharmacology