Sildenafil 20 mg vs 100 mg Tablets: Dose and Price Explained
Sildenafil 20 mg is the FDA-approved pulmonary hypertension dose sold as Revatio, while sildenafil 100 mg is the highest erectile-dysfunction dose in Viagra-equivalent generics. Knowing the difference can prevent under- or overdosing and save you hundreds of dollars per year.
Sildenafil 20 mg tablets are designed to be taken three times a day for pulmonary arterial hypertension (PAH), whereas a single sildenafil 50-100 mg tablet is taken as needed for erectile dysfunction (ED). The lower dose keeps lung blood-pressure down around the clock, and the higher dose gives a four-to-six-hour window for firmer erections. Because they serve different purposes, they are priced and covered by insurance differently, so swapping one for the other without medical advice is risky.
- Sildenafil is FDA-approved at 20 mg taken three times daily for PAH and at 25, 50, or 100 mg taken once before sex for ED.
- The 20 mg tablets cost pharmacies an average of $0.31 each, while 100 mg tablets average $0.58 each according to the federal NADAC file (cms.gov).
- Generic sildenafil for ED is available from Rx.com prescribers at 50 mg or 100 mg from $36 per month, with the online visit and shipping included.
- Splitting 100 mg ED tablets to approximate a 20 mg PAH dose is unsafe because the drug level would rise and fall instead of staying steady.
- Most headaches, flushing, or blurry vision occur within two hours of a 100 mg dose and usually resolve in four hours (Yoo et al., 2017).
What sildenafil 20 mg and 100 mg are
Both tablet strengths contain sildenafil citrate, a phosphodiesterase-5 (PDE-5) inhibitor that relaxes blood-vessel walls so blood flows more easily. Sildenafil 20 mg tablets are branded Revatio and carry an FDA indication for pulmonary arterial hypertension. The goal is to reduce strain on the right side of the heart all day, so the label specifies 20 mg by mouth every 8 hours for adults.
Sildenafil 100 mg tablets correspond to the highest approved erectile-dysfunction dose. The patient swallows one tablet 30-60 minutes before sexual activity, and should not repeat a dose within 24 hours. ED strengths also come as 25 mg and 50 mg tablets so prescribers can titrate based on effect and side effects.
How each dose works in the body
The PAH schedule maintains a low, steady concentration, while ED dosing creates a higher short-term spike. That spike is what boosts nitric-oxide signaling in penile tissue during arousal.
Most prescribers therefore advise taking sildenafil on an empty stomach or after a light meal for the most reliable onset.
Dose comparison and how to take
| Use | Label strength(s) | Typical schedule | Total daily amount |
|---|---|---|---|
| Pulmonary arterial hypertension (Revatio) | 20 mg tablets | 20 mg every 8 h (breakfast, mid-afternoon, bedtime) | 60 mg |
| Erectile dysfunction (Viagra-equivalent generics) | 25 mg, 50 mg, 100 mg tablets | Single dose 30-60 min before sex, max once daily | 25-100 mg |
Do not interchange schedules: Taking three 20 mg tablets at once to treat ED gives only about 60 % of the peak drug level seen with a single 100 mg tablet and may not work as well. Conversely, splitting a 100 mg tablet into five daily “PAH” doses creates big peaks and troughs that could worsen shortness of breath overnight.
For detailed administration tips, see our sildenafil-taking guide.
Price comparison and ways to save
The cash price of sildenafil can vary tenfold from pharmacy to pharmacy. Below are the 2026 average acquisition costs and typical retail ranges in U.S. pharmacies.
| Tablet strength | NADAC average cost to pharmacy (per tablet) | Typical retail range (no coupon) | Rx.com patient option |
|---|---|---|---|
| 20 mg | $0.31 | $1-$4 | Not supplied for ED; PAH patients compare prices locally with a free discount card |
| 50 mg | $0.44 | $2-$7 | generic sildenafil from Rx.com from $36/mo (online visit & shipping included) |
| 100 mg | $0.58 | $3-$10 | generic sildenafil from Rx.com from $36/mo (online visit & shipping included) |
Insurance coverage: Many plans cover Revatio for PAH but exclude sildenafil for ED. If your ED prescription is not covered, a free Rx.com discount card applied at a local pharmacy often beats the copay. You can also ask your prescriber about paying cash vs insurance.
Side effects by dose
Most adverse effects are dose-related.
| Side effect | 20 mg three times daily | Single 100 mg dose |
|---|---|---|
| Headache | 10 % | 16 % |
| Facial flushing | 8 % | 15 % |
| Nasal congestion | 4 % | 10 % |
| Visual color tinge | <1 % | 3 % |
| Indigestion | 5 % | 9 % |
Safety with other drugs: Any sildenafil dose can cause a dangerous drop in blood pressure if combined with nitrates such as nitroglycerin or with the pulmonary hypertension drug riociguat. Always tell your provider about heart medications.
Should you adjust your dose?
Trying to decide between 50 mg and 100 mg for ED?
Check the column that fits your situation:
✅ Stay at current dose
- You achieve an erection firm enough for sex most of the time
- Side effects are mild or absent
- Erection lasts 2-3 hours but not more than four
- No interaction warnings with your other medicines
🏥 Talk to your doctor
- Erections remain too soft after three separate attempts
- Severe headache, dizziness, or light-sensitivity every time you dose
- Any chest pain or shortness of breath after taking sildenafil
- You take alpha blockers or other blood-pressure pills
- Vision changes lasting longer than four hours
🚨 When to Contact Your Healthcare Provider
Contact your doctor immediately if you experience any of the following:
- Erection lasting more than 4 hours (priapism) - untreated priapism can cause permanent damage.
- Sudden loss of vision in one or both eyes - may signal non-arteritic anterior ischemic optic neuropathy.
- Sudden hearing decrease or ringing - rare but reported with PDE-5 inhibitors.
- Chest pain or pressure - could indicate serious heart problems when blood pressure drops.
- Severe dizziness or fainting - especially if combined with alcohol or other vasodilators.
- Allergic reaction - swelling of the face, lips, or throat or difficulty breathing.
- Shortness of breath that worsens - in PAH patients, may mean the dose is inadequate.
- Dark or bloody stool - possible sign of internal bleeding.
Scientific References
- Yoo H, Cho SM, Choi YW, et al. Comparison of pharmacokinetic characteristics of sildenafil citrate chewable tablets and film-coated tablets in healthy male subjects. Transl Clin Pharmacol. 2017.
- Murtadha M, Raslan MA, Fahmy SF, et al. Changes in the Pharmacokinetics and Pharmacodynamics of Sildenafil in Cigarette and Cannabis Smokers. Pharmaceutics. 2021.
- CMS Medicaid Data. data.medicaid.gov.
Frequently Asked Questions
Can I cut a 100 mg tablet into five 20 mg pieces for PAH?
No. Even if you could cut it evenly, the drug would leave your system in about six hours, leaving you unprotected overnight. Revatio’s label clearly requires 20 mg every eight hours for stable lung pressures.
Is 20 mg enough for erectile dysfunction?
Usually not. Clinical studies found that 25-50 mg works for most men, and up-titration to 100 mg is recommended only if 50 mg is insufficient and well tolerated.
Why is sildenafil cheaper online than at my local drugstore?
Telehealth programs like Rx.com contract with mail-order pharmacies and buy large generic lots, lowering the per-tablet cost. Local cash prices reflect smaller volume and retail mark-ups.
Does the 100 mg dose last longer than 50 mg?
No. Both doses share the same half-life of about four hours. The higher dose can provide stronger firmness but does not extend the duration of action.
What if I take nitrates and need help with ED?
Sildenafil is absolutely contraindicated with nitrates because the blood-pressure drop can be life-threatening. Ask your cardiologist about non-nitrate ED options such as vacuum devices or, in some cases, Quad Rx which does not interact with nitrates.
Can smoking affect how 20 mg or 100 mg works?
Yes. A small study found that cigarette smokers had 61 % higher drug exposure after a 50 mg dose, likely due to CYP3A4 inhibition (Murtadha et al., 2021). That could increase side-effect risk, so tell your doctor if you smoke.
Is it legal to buy 100 mg tablets and split them for a cheaper 50 mg dose?
Yes, if your prescription allows 100 mg and you use a proper tablet splitter. However, not all 100 mg generics are scored, and uneven halves can cause inconsistent results. Many men find it simpler to order the exact 50 mg strength.
Does generic sildenafil work as well as Viagra?
Users generally achieve the same effect at a fraction of the cost.
