OTTAWA, Sept. 19 /CNW Telbec/ - Health Canada is warning consumers not to use the natural health product Libidus because it contains an undeclared pharmaceutical ingredient, a modified form of vardenafil, which is similar to the active pharmaceutical ingredient found in the prescription drug Levitra. The use of Libidus could pose serious health risks, especially for patients with existing medical conditions such as heart problems, those taking heart medications, or those at risk for stroke.