Drug alert: People should not buy or use anti-impotence product Man Power which contains an undeclared Western drug ingredient.

The Department of Health urges people not to buy or use anti-impotence product Man Power which contains undeclared Western drug ingredient, tadalafil, which can cause serious side effects.

The product, seen for sale online, is not a registered pharmaceutical product in Hong Kong.

Tadalafil is usually used for treating male sexual dysfunction. Its side effects include low blood pressure, headache, vomiting, dizziness, and vision disturbances. It can interact with nitrates found in some prescription drugs, such as nitroglycerin for treatment of angina, and lower blood pressure to dangerous levels. Improper use of tadalafil can pose serious health risks, especially for people with heart problems.

Products containing tadalafil must be registered before sale and can only be sold on a doctor's prescription and under the supervision of a pharmacist.