Health Canada has issued a warning about Innerget and Megaton male sexual enhancement pills that have potentially deadly side effects.
The pills are marketed as natural health products and sold online by a Richmond, B.C., store called Lion King Health.
Three Innerget brand pills are touted as offering "instant erection", "everlasting strength" and "prolonged performance". The fourth - an unauthorized natural health product - is branded Megaton 2080.
"These products are promoted as male sexual stimulants and contain hidden prescription medications," Health Canada said in a statement.
The hidden ingredients include sildenafil analogs that may pose serious risks to the health of Canadians, particularly those with heart problems, or anyone taking any kind of nitrate drug such as nitroglycerine, as they can cause potentially life-threatening low blood pressure, it said.
"Individuals with heart problems including high blood pressure, a history of heart attack, stroke, abnormal heart beat or chest pain are at higher risk of cardiovascular side-effects if they engage in sexual activity, including if they use sildenafil or tadalafil to help them achieve an erection," it added.
Other possible side-effects include headache, facial flushing, indigestion, dizziness, abnormal vision and hearing loss.
Health Canada is urging anyone who has used the products to contact their doctor and report and adverse reactions to their toll-free line at 1-800-267-9675.