Sildenafil is a type of drug called a PDE5 inhibitor. PDE5 inhibitors work by blocking an enzyme called PDE5 (phosphodiesterase type 5), which in turn temporarily relaxes blood vessels and improves blood flow to the penis during sexual stimulation. For men who have trouble getting or staying hard, PDE5 inhibitors like sildenafil are typically the first line of treatment for erectile dysfunction.

Sildenafil is used to treat erectile dysfunction by improving blood flow to the penis. Sildenafil is also used to treat pulmonary arterial hypertension by relaxing blood vessels in the chest near the heart and lungs. The PDE5 enzyme is active in both the lungs and penis, which is why sildenafil is approved for the treatment of erectile dysfunction and pulmonary arterial hypertension.

Sildenafil typically lasts for at least 4 hours and up to 8-12 hours, but its effect is strongest 2-4 hours after it’s taken. As the amount of sildenafil in the bloodstream drops, so do the effects.

You should not experience erections that won't go away. If you have an erection that lasts more than 4 hours after taking sildenafil, get medical help right away.

Sildenafil typically starts working in about 15-30 minutes, but its peak effect begins for most men about one hour after it’s taken on an empty stomach. Keep in mind that food in the stomach can delay the absorption of sildenafil by up to an hour, and also that the timing of each individual’s response is a little bit different. 

Remember that sildenafil will only work when you are sexually aroused, but it should make it easier to get and sustain an erection during sexual intercourse.

In short, if you take more sildenafil than you were prescribed, that is too much sildenafil. You should take your prescribed dose (for example, 50mg or 100mg) no more than one time per day. Even if you have sex more than once per day, you still should only take sildenafil once.

If you feel that your prescribed dosage is not effectively treating your erectile dysfunction, message a clinician through our platform.

Yes, sildenafil is clinically proven to improve erections and is effective for 80% of men. If sildenafil does not work, it may be because it wasn’t taken soon enough before engaging in sexual activity, it was taken with food, or the dosing was incorrect.

Some men try sildenafil 4-5 times before coming to conclusions about whether or not it works for them - the mind and body sometimes need time to acclimate to the medication.

The most common side effects of sildenafil include headache, muscle aches, back pain, stuffy or runny nose, dizziness, facial flushing, rash, upset stomach or nausea, blurred vision or other visual changes and lowered blood pressure. If any of these effects do not go away over time or are particularly bothersome, talk to your clinician.

Serious side effects of sildenafil include sudden loss of vision, hearing problems and priapism, which is an erection lasting longer than four hours. These side effects are rare, but require immediate medical attention.

If you experience signs of an allergic reaction, such as hives or trouble breathing, seek emergency medical help.

Sildenafil has been shown to be safe for most men with erectile dysfunction. However, men with certain pre-existing medical conditions may be at greater risk for specific adverse effects.

If you have (or have ever had) heart problems (such as a heart attack), heart disease, irregular heartbeat, angina, chest pain, narrowing of the aortic valve, heart failure, heart surgery, pulmonary hypertension including pulmonary arterial hypertension, stroke, low blood pressure, high blood pressure, a deformed penis shape (Peyronie’s Disease), priapism (an erection that lasts for more than 4 hours), sickle cell anemia, multiple myeloma, leukemia, retinitis pigmentosa (a rare genetic eye disease), severe vision loss (such as NAION), bleeding problems, stomach ulcers, liver problems or kidney problems (such as kidney dialysis), you may be at higher risk for adverse effects.

If you have any of these health conditions, or any other health condition, tell your clinician. Your clinician should be aware of all medical conditions, prescription drugs and over-the-counter medications that you are taking.

Sildenafil does have known drug interactions with some other prescription medications. Sildenafil interacts with nitrates (nitroglycerin), guanylate cyclase stimulators (riociguat), alpha-blockers, HIV protease inhibitors (ritonavir, indinavir sulfate, saquinavir, atazanavir sulfate), oral antifungal medicines (ketoconazole, itraconazole), antibiotics (clarithromycin, telithromycin, erythromycin) and other high blood pressure drugs.

Be sure to avoid taking sildenafil at the same time as any nitrate medications (eg, nitroglycerin, isosorbide, etc) or other PDE5 inhibitors, including Revatio®, Cialis® (tadalafil), Levitra® (vardenafil) and Stendra® (avanafil).

Better yet, give your provider a list of all medications you are taking to get professional medical advice.