Health alert: People should not buy or take this red and yellow capsule labelled "Lu Quan".

The Department of Health urges people not to buy or use a red and yellow capsule labelled "Lu Quan" which is found to contain an undeclared drug that may cause serious side effects.

A 73-year-old man - who had bought the product in Shenzhen and taken it - was admitted to Kwong Wah Hospital on August 13 after being found unconscious. His blood glucose level was very low on admission.

Glibenclamide and sildenafil, which are used to treat diabetics and male sexual dysfunction, were found in his urine. He recovered and was discharged on August 19.

Glibenclamide can cause nausea and gastro-intestinal upset. Improper use may cause a significant fall in blood sugar levels with serious health consequences and even death.

Sildenafil's side effects include low blood pressure, headache, vomiting, dizziness, and blurred vision. It may interact with nitrates in some prescription drugs and lower blood pressure to dangerous levels. Improper use may pose serious health risks, especially for patients with heart problems.

Products with either sildenafil or glibenclamide must be registered in Hong Kong before sale and can only be sold on a doctor's prescription and under a pharmacist's supervision.