However, the U.S. Food & Drug Administration ruled in 1987 that pentoxyverine was not generally recognized as safe and effective and ordered it to be removed from the over-the-counter market.

[7][8] Pentoxyverine is contraindicated in persons with bronchial asthma[5] or other kinds of respiratory insufficiency (breathing difficulties), as well as angle-closure glaucoma.

[5] The most common side effects (seen in more than 1% of patients) are upper abdominal (belly) pain, diarrhoea, dry mouth, and nausea or vomiting.

[3][9] Overdosage leads to drowsiness, agitation, nausea and anticholinergic effects like tachycardia (high heart rate), dry mouth, blurred vision, glaucoma, or urinary retention.

[1][3][5] Pentoxyverine is believed to suppress the cough reflex in the central nervous system,[1] but the exact mechanism of action is not known with certainty.

The bioavailability of the suppositories, measured as area under the curve (AUC), is about twofold that of oral formulations, due to a first pass effect of over 50%.

[3] Pentoxyverine dihydrogen citrate, the salt that is commonly used for oral preparations, is a white to off-white, crystalline powder.