Tadalafil and sildenafil for erectile dysfunction
Tadalafil (Cialis) and sildenafil (Viagra) are FDA-approved tablets for erectile dysfunction, and tadalafil is also approved for prostate enlargement symptoms. They work well for many men, but they are dangerous with nitrate medicines and need a medication and heart review first.
Information current as of November 10, 2026. Educational only. Confirm everything here with your own clinician before starting, stopping or changing any medication.
At a glance
Drug class
Phosphodiesterase type 5 (PDE5) inhibitors. They widen blood vessels in the penis when there is sexual stimulation.
How it is taken
A tablet by mouth. Tadalafil can be taken as needed or once daily at a low dose. Sildenafil is taken as needed, about an hour before sex.
Approval status
Tadalafil: FDA-approved for erectile dysfunction (ED), benign prostatic hyperplasia (BPH) symptoms, or both. Sildenafil: FDA-approved for ED.
Who it is for
Men with ED, and men with BPH symptoms who may also have ED. Not for anyone who takes nitrates.
Main cautions
Never with nitrates or riociguat. Sudden vision or hearing loss and an erection longer than 4 hours need urgent care. Blood pressure can drop with alpha-blockers.
What they are
How tadalafil and sildenafil work
An erection needs blood to flow into the penis and stay there. The signal for that is a chemical called cyclic GMP. An enzyme called PDE5 breaks it down. Tadalafil and sildenafil block PDE5, so the signal lasts longer. They do not cause an erection by themselves and they do not raise testosterone or desire.
The two drugs differ in how long they act. Per the label, tadalafil taken as needed improved erectile function compared with placebo for up to 36 hours after dosing. Sildenafil is taken about an hour before sex, though the label allows 30 minutes to 4 hours.
Tadalafil is also approved for BPH, where the prostate presses on the urethra and causes weak stream and frequent urination. Men who are treating BPH with finasteride are one group in whom the combination is discussed in the label.
How it is taken
As needed versus once daily, per the label
Tadalafil
- As needed for ED: the recommended starting dose is 10 mg before anticipated sexual activity. It can be raised to 20 mg or lowered to 5 mg. The maximum frequency is once per day in most patients.
- Once daily for ED: the starting dose is 2.5 mg at about the same time every day, without regard to sexual activity. It can be raised to 5 mg.
- Once daily for BPH: 5 mg daily. With finasteride started together, 5 mg daily for up to 26 weeks.
- Once daily for ED and BPH: 5 mg daily.
- It can be taken with or without food.
Sildenafil
The usual dose is 50 mg taken as needed about an hour before sex. It can be raised to 100 mg or lowered to 25 mg. The label suggests starting at 25 mg in men over 65, with liver impairment, with severe kidney impairment, or when taking certain interacting drugs.
Daily low-dose tadalafil means the drug is always in your blood, so a man does not plan around a pill. It also means the interaction and blood-pressure rules apply every day. The label says to consider that continuous level when thinking about nitrates, alpha-blockers, blood pressure drugs, strong CYP3A4 inhibitors and alcohol.
Safety
Warnings you should know before the first tablet
Never combine with nitrates
Both labels contraindicate use with any form of organic nitrate, whether regular or occasional, because the combination can drop blood pressure to dangerous levels. This includes nitroglycerin tablets or spray, isosorbide, and recreational amyl nitrite. The label also contraindicates tadalafil with riociguat. If a man who has taken tadalafil needs a nitrate in a life-threatening emergency, the label says at least 48 hours should have passed. For sildenafil, the label says it is unknown when nitrates can be given safely. Tell any emergency team what you took and when.
Sudden vision loss
Stop the drug and get care if vision is lost suddenly in one or both eyes. It can be a sign of non-arteritic anterior ischemic optic neuropathy (NAION). The label says an observational study estimated about a 2-fold increased risk, and that a causal link is not established.
Sudden hearing loss
Sudden decrease or loss of hearing, sometimes with ringing or dizziness, has been reported. Stop the drug and seek prompt medical care.
Priapism
An erection lasting more than 4 hours needs emergency treatment. Untreated, priapism can permanently damage erectile tissue. Sickle cell disease, multiple myeloma, leukemia and Peyronie’s disease raise the risk.
Common side effects are headache, indigestion, flushing, nasal congestion, and back pain or muscle aches. With tadalafil, back pain or muscle aches generally start 12 to 24 hours after dosing and typically resolve within 48 hours, per the label. Tadalafil is not recommended for men who had a heart attack in the last 90 days, among other groups the label lists. In three studies in adult men, tadalafil reduced sperm concentration in two of them, which matters if you are trying to conceive.
Interactions
Alpha-blockers, CYP3A4 inhibitors and alcohol
- Alpha-blockers (tamsulosin, doxazosin and similar). Both drug types lower blood pressure. For ED, a man should be stable on the alpha-blocker first, and the PDE5 inhibitor starts at the lowest dose. For BPH, the tadalafil label does not recommend combining it with an alpha-blocker, and says to stop the alpha-blocker at least a day before starting daily tadalafil. Sildenafil starts at 25 mg with an alpha-blocker.
- Strong CYP3A4 inhibitors such as ketoconazole, itraconazole and ritonavir slow tadalafil breakdown. The label caps as-needed tadalafil at 10 mg no more than every 72 hours, and daily tadalafil at 2.5 mg. With ritonavir, sildenafil is limited to 25 mg in 48 hours.
- Blood pressure medicines. Effects add together. Your physician may check your blood pressure after starting.
- Alcohol. Five or more units with tadalafil can add to blood pressure lowering and cause dizziness.
Cardiovascular safety
What we know about the heart
Sexual activity itself puts demand on the heart, so the label says ED treatment should not be used in men for whom sex is inadvisable because of their cardiovascular status. Tadalafil has mild blood-vessel-widening effects: in healthy volunteers, 20 mg lowered supine blood pressure by an average of 1.6/0.8 mm Hg compared with placebo.
An integrated analysis of 35 controlled trials (2,118 men on placebo, 5,228 on tadalafil) found cardiovascular adverse events were low and similar between the groups. The heart attack rate across all trials was 0.33 per 100 patient-years on tadalafil and 0.41 on placebo (Jackson, see sources). These were trials of selected men, and they cannot show what happens in every man with heart disease. Serious cardiovascular events have also been reported after marketing in people who had risk factors.
With testosterone therapy
How tadalafil fits with low testosterone
ED has many causes besides testosterone: blood vessels, diabetes, nerves, medicines, stress and sleep. Low testosterone lowers desire and can contribute, but fixing the number does not always fix the erection.
A randomized trial put this to the test. Researchers took 140 men aged 40 to 70 with ED and low testosterone, optimized sildenafil first, then added testosterone gel or placebo for 14 weeks. Sildenafil alone raised erectile function scores by 7.7 points on average. Adding testosterone did not improve scores beyond placebo (difference 2.2, 95 percent CI -0.8 to 5.1) (Spitzer 2012). It did not test testosterone without sildenafil.
That is why the two are often used together, each for its own job. Read about the testosterone side on the testosterone page, and about low testosterone in general in this overview. The American Urological Association ED guideline says patients should be told about every treatment that is not contraindicated and that care should rest on shared decision-making.
Summit’s role
What Summit does with tadalafil
Summit Men includes tadalafil, along with testosterone, a GLP-1 through 10 mg in 2 mg steps, oral finasteride or minoxidil, and labs. Dr. Miranda prescribes it after a physician evaluation, and Summit is telehealth only. That evaluation includes your medicine list, with a specific question about nitrates, and your blood pressure and heart history.
Testosterone is a Schedule III controlled substance and follows state telehealth rules, with symptoms plus two morning total testosterone readings below 300. Nothing here promises that any treatment will be prescribed. Sildenafil is covered here for comparison. See pricing for what is included.
Common questions
Questions people ask
Is tadalafil FDA-approved?
Yes. Cialis (tadalafil) is FDA-approved for erectile dysfunction, for the signs and symptoms of benign prostatic hyperplasia, and for both together. Sildenafil (Viagra) is FDA-approved for erectile dysfunction.
Is daily tadalafil different from taking it as needed?
Yes. Daily dosing is 2.5 mg to 5 mg every day and does not depend on timing of sex. As-needed dosing starts at 10 mg before sexual activity. Both are on the label.
Can I take tadalafil with nitroglycerin?
No. Any form of nitrate, regular or occasional, is contraindicated with tadalafil and sildenafil because blood pressure can fall dangerously. Tell your physician about every medicine you take.
What should I do if I lose vision or hearing suddenly?
Stop the drug and seek medical care right away. Sudden vision loss can be a sign of NAION, and sudden hearing loss has been reported. The label does not establish that the drug caused either.
Can I take tadalafil if I am on testosterone therapy?
Yes, they are commonly used together. A trial of men with ED and low testosterone found that adding testosterone to sildenafil did not improve erectile function beyond placebo. Your physician decides what fits you.
Sources
Where this comes from
All retrieved November 10, 2026.
- Cialis (tadalafil) prescribing information. Eli Lilly. DailyMed. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895
- Viagra (sildenafil citrate) prescribing information. Pfizer. DailyMed. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=0b0be196-0c62-461c-94f4-9a35339b4501
- Jackson G et al. Update on clinical trials of tadalafil demonstrates no increased risk of cardiovascular adverse events. J Sex Med 2004. https://pubmed.ncbi.nlm.nih.gov/16422970/
- Spitzer M et al. Effect of testosterone replacement on response to sildenafil citrate in men with erectile dysfunction: a parallel, randomized trial. Ann Intern Med 2012. https://pubmed.ncbi.nlm.nih.gov/23165659/
- Burnett AL et al. Erectile Dysfunction: AUA Guideline. J Urol 2018. https://pubmed.ncbi.nlm.nih.gov/29746858/
- Bhasin S et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2018. https://pubmed.ncbi.nlm.nih.gov/29562364/
Confirm with your provider. This page is general education, not medical advice, and it does not diagnose or treat anything. Every medication carries risks and is not right for everyone. Medication is prescribed only after a physician evaluation determines it is appropriate for you. Individual results vary and no outcome is guaranteed. Information current as of November 10, 2026.
Next step
Tell the physician about every medicine you take
Dr. Miranda reviews your medicines, blood pressure and history first, including any nitrate or alpha-blocker.