Those with a history of blood pressure or heart issues, hormonal imbalances, mental health issues, and diabetes should consult their doctor before trying PDE5 inhibitors. This finding is consistent with the inhibition of PDE6, which is involved in phototransduction in the retina. The changes from baseline in scoring on the two end point questions frequency of successful penetration during sexual activity and maintenance of erections after penetration were highly statistically significantly in favor of VIAGRA. These effects on the metabolite are not expected to be of clinical consequence. It may be difficult to remain firm despite wanting to have sex.Branded Viagra: $90 per 25 mg, 50 mg, or mg pill Generic Cialis (tadalafil): $11 per 5 mg pill, $44 per 10 mg or 20 mg pill Generic Cialis Daily (tadalafil): $8 per mg or 5 mg pill. Sildenafil (Viagra) and tadalafil (Cialis) are the most commonly prescribed medications for ED, and they have the longest track record. For occasional use, most people start with sildenafil. For regular use, tadalafil can be a better fit. Some people prefer to alternate between medications. All ED meds are equally safe and effective. $12 View other PDE5 Inhibitors Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. It is also used to treat pulmonary arterial hypertension, a serious heart and lung condition. This drug is more popular than comparable drugs. It is available in generic and brand versions.