Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Revatio) is used to improve the ability to exercise in adults with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the lungs, causing shortness of breath, dizziness, and tiredness). Children should not usually take sildenafil, but in some cases, a doctor may decide that sildenafil (Revatio) is the best medication to treat a child’s condition. Sildenafil is in a class of medications called phosphodiesterase (PDE) inhibitors. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. This increased blood flow can cause an erection. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily.

If you are taking sildenafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. Sildenafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus (HIV).

Sildenafil comes as a tablet and suspension (liquid; Revatio only) to take by mouth.

If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph. Take sildenafil as needed before sexual activity. The best time to take sildenafil is about 1 hour before sexual activity, but you can take the medication any time from 4 hours to 30 minutes before sexual activity. Sildenafil usually should not be taken more than once every 24 hours. If you have certain health conditions or are taking certain medications, your doctor may tell you to take sildenafil less often. You can take sildenafil with or without food. However, if you take sildenafil with a high-fat meal, it will take longer for the medication to start to work.

If you are taking sildenafil to treat PAH, follow your doctor’s directions and the guidelines in this paragraph. You will probably take sildenafil three times a day with or without food. Take sildenafil at around the same times every day, and space your doses about 4 to 6 hours apart.

Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take sildenafil exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Shake the liquid well for 10 seconds before each use to mix the medication evenly. Use the oral syringe provided with your medication to measure and take your dose. Follow the manufacturer’s directions to use and clean the oral syringe. Do not mix the liquid with other medications or add anything to flavor the medication.

If you are taking sildenafil for erectile dysfunction, your doctor will probably start you on an average dose of sildenafil and increase or decrease your dose depending on your response to the medication. Tell your doctor if sildenafil is not working well or if you are experiencing side effects.

If you are taking sildenafil for PAH, you should know that sildenafil controls PAH but does not cure it. Continue to take sildenafil even if you feel well. Do not stop taking sildenafil without talking to your doctor.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

How does Viagra work?

Viagra  works by relaxing muscles in blood vessel walls to help increase blood flow to the penis, making it easier to get and maintain an erection. Viagra is only effective if there is sexual stimulation, such as that occurring during sexual intercourse. When stimulation first happens, Viagra helps increase blood flow to the penis and then works to help maintain an erection.

According to the Boston University School of Sexual Medicine, erectile dysfunction affects up to 52% of men between the ages of 40-70, many of whom turn to erectile dysfunction medications to help with their symptoms. Viagra is a type of erectile dysfunction drug called a phosphodiesterase 5 inhibitor. PDE5 inhibitors keep a particular enzyme called phosphodiesterase type-5 (PDE5) from acting too quickly. If PDE5 acts slower, then a substance that’s responsible for relaxing muscles and widening blood vessels can do its job.

Viagra will not be as effective for people with certain conditions. You may not get the full benefits of Viagra if you are sick, fatigued, or intoxicated. Alcohol can worsen the side effects of viagra and potentially make erectile dysfunction worse.

You should take Viagra on an empty stomach about one hour before sex. It starts working within 30 to 60 minutes, but an erection requires sexual stimulation.

“Some patients experience the effects of Viagra within 20 to 30 minutes after taking the medication,” says Amber Williams, Pharm.D., a compounding pharmacist at Family Pharmacy in Sarasota. “However, if the dose is taken with a high-fat meal, the peak response may be delayed for up to 60 minutes. In most patients, the effects of Viagra will last for up to two hours. A duration of two hours or less indicates that an appropriate dose was taken. If the duration is greater than four hours, medical attention should be sought out immediately to avoid damaging effects on the tissues.”

How long does Viagra last?

The amount of time that Viagra will last depends on many factors. Dosage, age, and overall health are just some of the factors that can impact how well Viagra works and lasts for someone. A smaller dosage of Viagra (recommended for older adults) means that the drug won’t last as long.

The average dose of Viagra is 25-100 mg, taken 30 to 60 minutes, or up to four hours before sexual activity. For adults over the age of 65, the recommended dose is 25 mg. Many older adults have slower metabolisms, which means that a lower dose may last longer for them in comparison to a younger person taking a small dose.

Take Viagra before sexual activity, as it takes time for Viagra to absorb into the bloodstream. It’s unlikely that Viagra will help you last longer during sexual intercourse. However, some men—depending on their metabolism—may experience multiple erections while Viagra is in their system. Once it starts working, Viagra typically lasts for up to four or five hours. If you do experience an erection that lasts longer than this (priapism) or is painful, it may be time to seek medical advice.

Viagra won’t necessarily help you recover faster after orgasm. Recovery time (called the refractory period) varies for each individual. Consuming alcohol while taking Viagra can make the medication less effective by decreasing blood flow to the penis.

For people with certain medical conditions, Viagra might not last as long. Feelings of anxiety, depression, or nervousness often cause Viagra not to last as long or be as effective. Having a heart problem, heart disease, diabetes, or other nervous system problems can also cause Viagra not to last as long.

Certain medications may interact negatively with Viagra and interfere with its effectiveness. Drugs that lower blood pressure can interact with Viagra to cause dangerously low blood pressure. Don’t take Viagra with any medication that contains nitrates, which includes street drugs called “poppers” like amyl nitrate and butyl nitrate. Antifungal and antiviral medications may increase the amount of Viagra in the bloodstream, which can lead to toxicity. Talking with your healthcare provider is the best way to determine if Viagra will cause any drug interactions.

Viagra Precaution