What Is Sildenafil? How It Works & What to Expect

Sildenafil is one of the most well-known medications for erectile dysfunction. It's the active ingredient behind the brand name Viagra®, and it's been helping men get and keep stronger erections for decades.

In this guide, we'll break down exactly what sildenafil is, how it works, the benefits it can bring, and how BlueChew makes it available in a fast-acting sublingual tablet called SIL.

• Sildenafil is a PDE5 inhibitor that increases blood flow to the penis, supporting stronger, longer-lasting erections.
• It's the same active ingredient found in brand-name Viagra, with a safety and effectiveness track record spanning almost 30 years. In clinical trials, 67–89% of men taking PDE5 inhibitors had improved erections.
• BlueChew offers sildenafil as SIL, a 45 mg compounded sublingual tablet that may start working in as little as 15 minutes, with no water or swallowing required.
• Take SIL 15–30 minutes before sexual activity. Its effects last about 4–6 hours.
• Ready to see if SIL is right for you? Take the quiz.

Sildenafil is a prescription medication first made popular as the original erection-enhancing treatment, better known under the brand name Viagra. It belongs to a class of drugs called phosphodiesterase-5 (PDE5) inhibitors, and it works by increasing blood flow to the penis to support a firm, lasting erection.

BlueChew offers sildenafil as SIL, a convenient 45 mg compounded sublingual tablet prescribed for as-needed use. Because SIL is a compounded medication, it's custom-made in the dosage and form best suited to our patients' needs, rather than a one-size-fits-all pill.

Why a Sublingual Tablet Instead of a Pill?

Sublingual tablets have a few distinct advantages over traditional pills:

• Convenience: Take it anywhere and let it dissolve under your tongue. No water and no swallowing.
• Speed: Research has shown sublingual medications like SIL may kick in faster than standard pills, with sublingual sildenafil potentially taking effect in as little as 15 minutes.
• Discretion: A small, easy-to-carry tablet that doesn't look like a prescription bottle.

SIL, containing the active ingredient sildenafil, is a type of medication known as a phosphodiesterase-5 inhibitor, or PDE5i for short.

It works by blocking an enzyme called phosphodiesterase-5 (PDE5). During arousal, nitric oxide (NO) is released in the penis, which raises levels of a molecule called cyclic guanosine monophosphate (cGMP). cGMP relaxes the smooth muscle in blood vessels so they can widen. PDE5 normally breaks cGMP down.

By stopping PDE5 from breaking down cGMP, sildenafil keeps those blood vessels relaxed longer, allowing more blood to flow to the penis.

As blood flow increases, the tissue becomes engorged, making it easier to achieve and maintain a hard, long-lasting erection during sexual stimulation.

Thanks to its blood-flow-enhancing properties, sildenafil can help you achieve and maintain harder erections, with patients reporting significant improvements in erection quality and erectile function. The rate of improvement has also been found to be higher in younger patients, so gains may be faster and more pronounced if you're under 60.

Beyond erection quality, sildenafil has been linked to increased intercourse success rates, sexual satisfaction, orgasms, and even improved quality of life, benefits reported by both patients and their partners. These improvements can also boost confidence and self-esteem in and out of the bedroom, and have been linked to stronger sexual and social relationships.

Sildenafil was first FDA-approved for erectile dysfunction in 1998. Under a different brand name, it's also FDA-approved to treat pulmonary arterial hypertension, a type of high blood pressure in the lungs.

Researchers are studying other possible benefits, but this research is early, and SIL is not approved or prescribed for any of these uses:

• Improved exercise capacity in some people with heart conditions
• Modestly lower blood pressure
• A possible link to lower risk of heart attack in men with type 2 diabetes, based on observational data

Interested in learning more? Read our full post on the potential health benefits of sildenafil.

SIL is prescribed for as-needed use, so it's best taken before an evening out or date night when the opportunity for intimacy might arise. Your BlueChew provider will give you specific instructions, but generally, SIL is taken 15–30 minutes before sexual activity. Don't take it more often than your provider recommends.

Once taken, SIL can help you get erections for about 4 to 6 hours. Take it 15–30 minutes before an expected intimate moment. It only causes an erection with sexual stimulation.

A few tips for best results:

• Take SIL on a relatively empty stomach. High-fat meals may slow absorption.
• Skip the cocktail. Alcohol can reduce the medication's effectiveness.
• Avoid grapefruit juice, which may alter how sildenafil works in your body.

Because SIL requires some planning and has a shorter duration than some other options, it may not be the right fit for everyone. If you want a longer window, TAD lasts up to 36 hours. Our side-by-side comparison of BlueChew's medications can help you decide, or you can talk it through with a BlueChew provider.

SIL is typically well tolerated, but like all prescription medications, it carries a risk of side effects. Sildenafil has a solid safety and effectiveness track record spanning almost 30 years, but it's still worth knowing what to look out for.

Common side effects:

• Skin flushing
• Headache
• Indigestion
• Mild nasal congestion
• Muscle pain

Less common but more serious: a prolonged erection lasting more than 4 hours, low blood pressure, sudden vision loss, irregular heartbeat, or sudden decrease in hearing. If you experience any of these, contact your doctor or a member of the BlueChew medical team right away. Although rare, allergic reactions are also possible; seek emergency care immediately if symptoms are severe.

Who shouldn't take SIL: Don't take SIL if you use nitrates for chest pain or guanylate cyclase stimulators, because the combination can cause a dangerous drop in blood pressure. Share all your current medications and health conditions in your intake so your provider can confirm SIL is safe for you. For the full list, see our safety information page.

Interested in getting your hands on an erectile dysfunction prescription? BlueChew has got you covered.

Select a plan, complete an online intake, and you’re done. A medical provider will review your information and, if appropriate, prescribe your plan, which will be shipped directly to your door.

No doctor appointments or patient support charges make it a stress-free experience.

Plus, there’s no commitment—you can easily cancel or switch plans anytime.
Click here to explore all plan options for treatments at BlueChew.

Is sildenafil the same as Viagra? 

Both SIL and Viagra contain the active ingredient sildenafil. SIL is a compounded medication in sublingual form. Compounded medications are custom-made by state-licensed pharmacies and are not FDA-approved, but they contain the same active ingredient as their brand-name counterparts.

Why use a sublingual tablet instead of a pill? 

Sublingual SIL is convenient: no water needed, and it's easy to take anywhere. Research suggests sublingual sildenafil may also start working faster than a swallowed pill.

How long before sex should I take SIL? 

Take SIL 15–30 minutes before sexual activity, or as your provider directs.

What are the sexual health benefits of sildenafil? 

SIL enhances blood flow to the penis for harder, longer-lasting erections, and has been linked to improved sexual satisfaction and confidence for both users and partners. SIL does not protect against sexually transmitted infections, so continue practicing safe sex.

What are the other potential health benefits of sildenafil? 

Sildenafil is FDA-approved under a different brand name to treat pulmonary arterial hypertension. Early research is also exploring possible effects on exercise capacity, blood pressure, and heart health, but SIL is not approved or prescribed for these uses. See our full health benefits post for more.

How long does SIL last? 

SIL's effects typically last 4 to 6 hours. For best results, take it 15–30 minutes before intimacy and avoid high-fat meals, alcohol, and grapefruit juice.

Does SIL make you last longer in bed? 

SIL helps you get and keep an erection when you're aroused. It isn't designed to delay ejaculation, but firmer, more reliable erections can take some of the pressure off.

How do I get a prescription for SIL through BlueChew? 

Select your plan, create an account, and complete a medical intake form. A licensed provider usually reviews your history within 24 hours and prescribes SIL if appropriate.

What are the potential side effects of sildenafil? 

Common side effects include headache, flushing, indigestion, nasal congestion, and muscle pain. Less common but serious side effects include blurred or sudden vision loss, a prolonged erection, sudden hearing loss, low blood pressure, chest pain, and irregular heartbeat. Contact your doctor immediately if you experience any of these.

Don't take SIL with nitrates or guanylate cyclase stimulators. People with certain conditions, like sickle cell anemia or pulmonary veno-occlusive disease, should discuss suitability with a provider, and you should disclose all current medications to avoid interactions.