Do not take more or less of it or take it more often than prescribed by your doctor. Cialis is also highly effective in reducing the symptoms of BPH. Comparison with actions of other PDE5 inhibitors[ edit ] Sildenafil and vardenafil inhibit PDE6, an enzyme found in the eye, more than tadalafil. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Your doctor will probably tell you not to take tadalafil if you are taking nitrates.How much is generic Cialis at Walmart? As of October , generic Cialis costs $ at Walmart. Is Cialis available as a generic? Cialis is available as the generic drug tadalafil. A generic drug is an exact copy of the active drug in a brand-name medication . Cialis is available as the generic drug tadalafil. A generic drug is an exact copy of the active drug in a brand-name medication and is considered just as safe and effective.