The Department of Health urges consumers not to buy or use four slimming products which contain undeclared Western drug ingredients that can cause serious side effects.

The products were purchased online during the department's market surveillance exercise. They are not registered pharmaceutical products. Sibutramine and its analogue, as well as phenolphthalein, were found in them.

Sibutramine is a Western medicine used as an appetite suppressant. Its side effects include increased blood pressure and heart rate, psychosis and convulsions. People with heart problems should not take it.

Products with sibutramine must be registered before they can be sold in Hong Kong on a doctor's prescription and dispensed under a pharmacist's supervision.

The sibutramine analogue, being chemically similar to sibutramine, is expected to have the same side effects as sibutramine.

Phenolphthalein was once used for treating constipation but has been banned for its cancer-causing effect.

The department called on consumers not to use the products and to see a doctor if they feel unwell after taking them.