These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. Men with untreated ED had relatively low baseline scores for all aspects of sexual function measured again using a 5-point scale in the IIEF. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects. The frequency of patients reporting improvement of erections in response to a global question in four of the randomized, double-blind, parallel, placebo-controlled fixed dose studies patients of 12 to 24 weeks duration is shown in Figure 7. Viagra is not for use by females. The pharmacokinetics of sildenafil are dose-proportional over the recommended dose range. · Viagra is meant to be used as a long-term treatment. If you and your doctor determine that Viagra is safe and effective for you, you’ll likely take it long term. Frequently asked questions. Medications. Your doctor may first recommend proven ED medications, such as tadalafil (Cialis) and sildenafil (Viagra). Tadalafil can be effective up to 36 hours after taking it. Sildenafil is. If you have these symptoms, stop taking VIAGRA and contact a doctor right away. have or have had heart problems such as a heart attack, irregular heartbeat, angina, chest pain, narrowing of the aortic valve, or heart failure. have had heart surgery within the last 6 months. have pulmonary hypertension. have had a stroke.