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Side Effects of Erection Medicines: Headaches to Emergencies
The short answer
The common side effects of sildenafil, tadalafil and vardenafil are headache (about 11 to 28 percent depending on drug and dose), flushing, stuffy nose and indigestion, plus back pain and muscle aches with tadalafil and a temporary color tinge to vision with sildenafil. They are dose-related and usually pass as the medicine wears off. The rare emergencies are an erection lasting more than 4 hours, sudden loss of vision or hearing, and a dangerous blood pressure drop when combined with nitrates; each needs immediate care.
Every good horse has a quirk. One tosses its head, one hates puddles, one will not stand still for the farrier. You learn the quirk, you ride anyway, and you also learn the one or two signs that mean get off right now. Erection medicines are the same: the common side effects are quirks, and the rare ones are the get-off-now signs.
Most men get nothing, or a mild headache, a warm face and a stuffy nose that fade with the medicine. A few get something that needs an emergency room. Here are the label numbers for both.
We all need a little help getting hung sometimes. Reading the label is part of the help.
Key facts
- Headache is the most common side effect of all three: 16 to 28 percent on sildenafil depending on dose, 11 to 15 percent on tadalafil, 15 percent on vardenafil, against 4 to 7 percent on placebo 123.
- Flushing, nasal congestion and indigestion are the next most common, and all rise with the dose 123.
- Tadalafil adds back pain (3 to 6 percent) and muscle aches (1 to 4 percent) that start 12 to 24 hours after a dose and usually resolve within 48 hours 2.
- Sildenafil adds a temporary color tinge to vision, light sensitivity or blurring in 1 to 11 percent of men, most often at 100 mg 1.
- The emergencies are an erection lasting more than 4 hours, sudden loss of vision or hearing, and a severe blood pressure drop with nitrates or poppers 123.
- Studies suggest about a 2-fold increase in the risk of NAION, a rare cause of sudden vision loss, within 5 half-lives of a dose 12.
What are the most common side effects of erection medicines?
Headache, flushing, a stuffy nose and indigestion, in roughly that order, and they track the dose. In sildenafil’s fixed-dose trials, headache affected 16 percent of men at 25 mg, 21 percent at 50 mg and 28 percent at 100 mg, versus 7 percent on placebo 1. Tadalafil’s as-needed trials reported headache in 11 to 15 percent and indigestion in 4 to 10 percent 2; vardenafil’s reported headache in 15 percent, flushing in 11 percent and rhinitis in 9 percent 3. The table has the rest.
| Side effect | Sildenafil, 25 to 100 mg 1 | Tadalafil, as needed 2 | Vardenafil 3 |
|---|---|---|---|
| Headache | 16 to 28% (placebo 7%) | 11 to 15% (5%) | 15% (4%) |
| Flushing | 10 to 19% (2%) | 2 to 3% (1%) | 11% (1%) |
| Stuffy or runny nose | 4 to 9% (2%) | 2 to 3% (1%) | 9% (3%) |
| Indigestion | 3 to 17% (2%) | 4 to 10% (1%) | 4% (1%) |
| Back pain | 3 to 4% (2%) | 3 to 6% (3%) | 2% (2%) |
| Muscle aches | 2 to 4% (1%) | 1 to 4% (1%) | Not listed |
| Vision changes | 1 to 11% (1%) | Not listed | Not listed |
| Dizziness | 3 to 4% (2%) | Not listed | 2% (1%) |
These are the quirks, the price of dilating blood vessels in places other than the one you had in mind. MedlinePlus lists the same cluster for each drug 456.
Why does tadalafil cause back pain and sildenafil change vision?
Because each molecule has its own signature. Tadalafil’s label documents back pain and muscle aches that typically begin 12 to 24 hours after a dose and resolve within 48 hours; with a 17.5-hour half-life, its side effects can linger as the drug does 2. See the tadalafil page for how the daily low dose changes the picture.
Sildenafil’s vision effect is described on the label as mild to moderate and transient, predominantly a color tinge, but also increased sensitivity to light or blurred vision 1. It was reported by 1 percent of men at 25 mg, 2 percent at 50 mg and 11 percent at 100 mg 1. It is not the sudden vision loss discussed below, and it passes as the drug clears. Vardenafil carries a separate caution for men with a congenital long QT syndrome or on class IA or III antiarrhythmics, who should avoid it 3.
What are the rare but serious side effects?
Four, and every label names all four. First, priapism: an erection lasting more than 4 hours, painful or not, requires immediate medical attention 123. Mayo Clinic explains why: blood trapped in the penis is deprived of oxygen, which can damage or destroy tissue, and untreated priapism can cause erectile dysfunction 8.
Second, sudden loss of vision in one or both eyes, which can be a sign of nonarteritic anterior ischemic optic neuropathy, or NAION 123. The baseline is rare, 2.5 to 11.8 cases per 100,000 men aged 50 and older each year, and observational studies suggest roughly a 2-fold increase within 5 half-lives of a dose 12. Men with a “crowded” optic disc, an anatomical variant an eye doctor can see, are at higher risk 12.
Third, sudden decrease or loss of hearing, sometimes with ringing in the ears or dizziness; the labels say stop the medicine and seek prompt medical attention 1234. Fourth, a severe blood pressure drop with nitrates in any form, including nitroglycerin, isosorbide and poppers, which is why nitrates are an absolute contraindication 123. Our nitrates article covers that one in depth.
What should you do about a headache, flushing or congestion?
Start with the dose and the timing. The side effects above rise with dose, so a man with a pounding headache at 100 mg of sildenafil often does fine at 50 mg 1. For sildenafil and vardenafil, a lighter meal helps, and for all three, less alcohol: heavy drinking with tadalafil in particular adds headache, dizziness and a drop in standing blood pressure 25.
Do not double up if the first pill seems slow; the labels set a maximum of one dose per day and say combining two erection medicines has not been studied and is not recommended 12. If side effects persist, switching molecules is common and reasonable. Mayo Clinic lists the same common effects for the whole class and the same two serious ones, hearing or vision loss and an erection that will not go away 7.
Which side effects mean stop and get help now?
An erection past 4 hours, sudden vision loss, sudden hearing loss, chest pain, or fainting. That is the labels’ emergency list, and MedlinePlus repeats it for all three drugs 123456. Do not wait for a prolonged erection to resolve on its own; the tissue damage clock is running 8.
Dizziness on standing, especially after alcohol or in men taking blood pressure medicine or alpha blockers, is the lesser cousin: sit down, do not drive, and call your clinician if it recurs 123. Our article on erection medication and blood pressure medicine covers the fixes.
When to talk to a clinician
Call 911 or go to an emergency room for an erection lasting more than 4 hours, sudden loss of vision or hearing, chest pain during or after sex, or fainting 123. Never take these medicines with any nitrate, poppers or riociguat, and never stack two erection medicines 123.
Call sooner about a headache or back pain that makes you dread the next dose, new vision or hearing changes that are not sudden, or any side effect that lasts past the day after a dose 12. Tell your clinician every medicine you take, including alpha blockers, blood pressure medicines, antifungals and HIV medicines, since those change the safe dose 123.
Learn the quirks, respect the get-off-now signs, and let the consult that comes with every plan match you with the horse whose quirks you can live with.
Hard questions, straight answers
What is the most common side effect of sildenafil?
Headache. In the fixed-dose trials it affected 16 percent of men at 25 mg, 21 percent at 50 mg and 28 percent at 100 mg, compared with 7 percent on placebo. Flushing, indigestion and nasal congestion follow, and all of them rise with the dose, which is why a clinician often starts lower.
Why does tadalafil cause back pain?
The label does not explain the mechanism, but it documents the pattern: back pain in about 3 to 6 percent of men and muscle aches in 1 to 4 percent, typically starting 12 to 24 hours after a dose and resolving within 48 hours. Because tadalafil stays in the body far longer than sildenafil, its side effects can linger longer too.
Do erection pills cause vision problems?
Sildenafil can cause a temporary color tinge, light sensitivity or blurred vision, reported by 1 to 11 percent of men and most common at 100 mg. That is different from the rare emergency: sudden loss of vision in one or both eyes, which may signal NAION, an optic nerve problem. Studies suggest roughly a 2-fold increase in that already rare event shortly after a dose.
How long is too long for an erection after taking sildenafil or tadalafil?
Four hours. Every label says an erection lasting more than 4 hours, painful or not, needs immediate medical attention. Prolonged erections trap oxygen-poor blood in the penis, which can permanently damage tissue and cause erectile dysfunction if untreated.
Can I take something for the headache from erection pills?
Talk to your clinician about the simplest fixes first: a lower dose, taking sildenafil or vardenafil with a lighter meal, and going easy on alcohol, since alcohol and these medicines both lower blood pressure and add to headache. Ask before adding any other medicine; the answer depends on what else you take.
Sources
- FDA: sildenafil tablets, full prescribing information (brand-name original) ↗
- DailyMed: tadalafil tablets prescribing information ↗
- DailyMed: vardenafil hydrochloride tablets prescribing information ↗
- MedlinePlus: Sildenafil ↗
- MedlinePlus: Tadalafil ↗
- MedlinePlus: Vardenafil ↗
- Mayo Clinic: Erectile dysfunction, oral medications ↗
- Mayo Clinic: Priapism, symptoms and causes ↗
Information checked 2026-09-13 by LPMD Medical Group clinicians. This article is general education, not a diagnosis or a treatment plan for you. Your clinician and pharmacist provide the instructions for your actual prescription.