Sildenafil
PrescriptionWhat is Sildenafil?
Sildenafil is a prescription medication that treats erectile dysfunction, which is when a man has trouble getting or keeping an erection. It also treats pulmonary arterial hypertension, a rare condition where blood pressure in the lungs is too high. You may know this medicine by its brand name, Viagra, for ED treatment or Revatio for lung conditions.
This medication belongs to a group of drugs called PDE5 inhibitors. It works by relaxing blood vessels and improving blood flow to specific areas of the body. Sildenafil does not create an erection on its own. It only helps when you are already sexually stimulated.
Doctors have prescribed sildenafil since 1998 for millions of men worldwide. It comes in tablet form and typically starts working within 30 to 60 minutes. The effects can last for about 4 to 5 hours after taking it.
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Common uses
- Erectile dysfunction in adult men
- Pulmonary arterial hypertension to improve exercise capacity
- Off-label use for Raynaud phenomenon to improve blood flow
- Off-label use for altitude sickness prevention in some cases
How it works
Sildenafil blocks an enzyme called phosphodiesterase type 5, or PDE5 for short. This enzyme breaks down a substance called cGMP, which relaxes smooth muscle in blood vessels. When sildenafil blocks PDE5, cGMP levels stay higher for longer. This allows blood vessels to stay relaxed and open wider.
For erectile dysfunction, this improved blood flow helps the penis become erect during sexual activity. For pulmonary arterial hypertension, it relaxes blood vessels in the lungs. This lowers blood pressure in the lungs and makes it easier for the heart to pump blood. The medication only works in areas where the body naturally releases nitric oxide during arousal or other triggers.
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Dosage information
For erectile dysfunction, the typical starting dose is 50 mg taken about 1 hour before sexual activity. Your doctor may adjust this to 25 mg or 100 mg based on how well it works and any side effects. The maximum recommended dosing frequency is once per day. For pulmonary arterial hypertension, the usual dose is 20 mg taken three times daily, about 4 to 6 hours apart. Your doctor will determine the right dose and schedule for your specific condition.
Side effects
- Headache
- Flushing or warmth in the face, neck, or chest
- Upset stomach or indigestion
- Stuffy or runny nose
- Dizziness or lightheadedness
- Back pain or muscle aches
- Changes in color vision, such as blue tint
- Sensitivity to light
Serious side effects require immediate medical attention. These include an erection lasting longer than 4 hours, sudden vision loss, sudden hearing loss or ringing in the ears, chest pain, irregular heartbeat, shortness of breath, or swelling in the hands or feet. Stop taking sildenafil and seek emergency care if you experience these symptoms.
Drug interactions
- Nitrates such as nitroglycerin can cause dangerous blood pressure drops when combined with sildenafil
- Alpha-blockers for prostate or blood pressure may increase risk of low blood pressure
- Other blood pressure medications may have additive effects
- Riociguat and other pulmonary hypertension drugs should not be combined with sildenafil
- Certain antibiotics and antifungals can increase sildenafil levels in the blood
- HIV protease inhibitors may require dose adjustments
- Grapefruit juice can increase sildenafil levels and side effects
- Alcohol may increase risk of dizziness and low blood pressure
- Other ED medications should not be used at the same time
Blood test monitoring
Before starting sildenafil, your doctor may check your heart health and blood pressure to make sure the medication is safe for you. Regular monitoring of cardiovascular health is important, especially if you have heart disease or risk factors. Testosterone levels may also be checked, as low testosterone can contribute to erectile dysfunction. If you have diabetes or other conditions affecting blood vessels, your doctor may recommend regular blood tests to monitor kidney function, liver enzymes, and cholesterol levels. Men taking sildenafil should also have routine eye exams, particularly if they have diabetes or high blood pressure, to catch any vision problems early.
Related blood tests
Taking Sildenafil? Monitor your levels.
- Track how your body responds
- Catch side effects early with blood work
- Share results with your doctor
Frequently asked questions
Sildenafil typically starts working within 30 to 60 minutes after you take it. For best results, take it on an empty stomach, as food can slow absorption. The medication works only when you are sexually stimulated, not automatically. Effects can last for about 4 to 5 hours.
No, sildenafil is a prescription medication in the United States. You need a valid prescription from a licensed healthcare provider to purchase it. Rite Aid pharmacy services are returning soon and will require a prescription for this medication. Avoid buying sildenafil online without a prescription, as these products may be fake or unsafe.
Sildenafil is the active ingredient in Viagra. Viagra is the brand name version made by Pfizer. Generic sildenafil contains the same active ingredient and works the same way. The main difference is cost, as generic versions are usually much less expensive than brand name Viagra.
Yes, checking testosterone levels can be helpful before starting ED treatment. Low testosterone is a common cause of erectile dysfunction. If your testosterone is low, treating that may improve ED symptoms. Rite Aid offers blood testing that measures testosterone along with over 200 other biomarkers to help you understand your overall health.
For erectile dysfunction, sildenafil is usually taken as needed, not daily. The maximum frequency is once per 24-hour period. For pulmonary arterial hypertension, doctors prescribe a lower dose taken three times daily. Never change your dosing schedule without talking to your doctor first.
Headaches are one of the most common side effects of sildenafil. Drinking plenty of water and taking an over-the-counter pain reliever like acetaminophen may help. If headaches are severe or persistent, talk to your doctor. They may adjust your dose or suggest a different medication.
Sildenafil can be safe for men with controlled high blood pressure. However, it can lower blood pressure, especially when combined with blood pressure medications. Never take sildenafil if you use nitrates for chest pain, as this combination can cause dangerous blood pressure drops. Always discuss your full medical history with your doctor before starting this medication.
Blood tests help identify underlying causes of erectile dysfunction and ensure the medication is safe for you. Testosterone, blood sugar, cholesterol, and kidney function can all affect ED and cardiovascular health. Regular monitoring helps catch potential problems early. Rite Aid offers convenient blood testing with results for over 200 biomarkers twice per year.
Most side effects of sildenafil are temporary and go away within a few hours. Rarely, serious side effects can occur, such as permanent vision loss or hearing damage. An erection lasting longer than 4 hours, called priapism, requires immediate medical attention to prevent permanent damage. These serious side effects are uncommon but require prompt treatment.
Sildenafil can work for men with diabetes, though diabetes-related ED may be more difficult to treat. High blood sugar damages blood vessels and nerves over time. Keeping blood sugar well controlled improves ED treatment success. Your doctor may want to check your A1C and other diabetes markers regularly to ensure your condition is managed properly.