Sildenafil Headache: How Common Is It?

The Viagra label's headache rates by dose, how they compare with tadalafil, and the symptoms that are not routine.

Headache is the most common side effect of sildenafil. In the Viagra label's placebo-controlled trials in which men took it as needed, 16% of men on sildenafil reported a headache, against 4% on placebo.¹ The label does not say why, and it does not report how long the headaches last. This page sets out what the label does and does not tell you, and when a symptom should be treated as more than a nuisance.

How common is a headache on sildenafil?

The Viagra label reports adverse reactions in two sets of trials. In the fixed-dose studies, headache was reported by 16% of men on 25 mg (312 men), 21% on 50 mg (511 men) and 28% on 100 mg (506 men), compared with 7% of the 607 men on placebo.¹ In the flexible-dose studies, which match how the drug is meant to be used, it was 16% of 734 men on sildenafil and 4% of 725 on placebo.¹

Two points follow. Headache rose with the dose in the fixed-dose studies, and most men who had one still carried on: across the flexible-dose studies the rate of stopping because of any side effect was 2.5% on sildenafil and 2.3% on placebo.¹ The label gives no breakdown of how many of the stoppers had a headache.

What other side effects come with the headache?

The label lists headache, flushing, dyspepsia (indigestion), abnormal vision, nasal congestion, back pain, muscle pain, nausea, dizziness and rash as the reactions reported by at least 2% of men.¹ In the fixed-dose studies, flushing affected 10% to 19% of men depending on dose, and dyspepsia 3% to 17%.¹

The vision effect is usually a colour tinge, extra sensitivity to light or blurred vision. The label describes it as mild and transient, and links it to sildenafil acting on a related enzyme in the retina, PDE6, which sildenafil blocks less selectively than its target, PDE5.¹ MedlinePlus lists headache, heartburn, diarrhea, nausea, flushing, nosebleeds, muscle and back pain, a blue tinge to vision and nasal congestion as the effects to mention to a doctor if they are severe or do not go away.²

Does sildenafil cause more headaches than tadalafil?

The two labels report different trial designs, so the numbers cannot be lined up as a contest, and the Viagra label itself warns that rates from one drug's trials cannot be directly compared with another's.¹ They are still useful as a sense of scale. In the Cialis label's as-needed ED trials, headache was reported by 11% of men on 5 mg or 10 mg and 15% on 20 mg, against 5% on placebo.³ For once-daily 2.5 mg or 5 mg, the figures were 3% and 6%, against 5% on placebo.³

Both drugs cause headache more often than placebo at the doses used as needed. Which one a given man tolerates better is an individual matter, and our guides to tadalafil side effects and choosing between sildenafil and tadalafil cover the tadalafil side.

Does a lower dose cause fewer headaches?

In the fixed-dose data, the headache rate was lower at 25 mg (16%) than at 100 mg (28%).¹ That pattern is why the label lets the prescriber move the dose up or down within a range rather than fix it.¹ It does not mean a lower dose is the right answer for every man, because the lower dose may also be less effective, and the label does not tell patients to adjust the dose themselves. If headaches are the problem, the dose is a question for the prescriber. Our page on sildenafil doses sets out the labeled strengths.

When is a headache a reason to call a doctor?

MedlinePlus advises telling a doctor about side effects that are severe or do not go away.² The label and MedlinePlus separately name effects that are not routine and call for prompt attention:

• Sudden loss of vision in one or both eyes, which may be a sign of non-arteritic anterior ischemic optic neuropathy (NAION). The label says to stop the drug and seek medical care.¹
• Sudden decrease or loss of hearing, which may come with ringing in the ears and dizziness.¹
• An erection lasting more than four hours.¹
• Chest pain, fainting or worsening shortness of breath, which MedlinePlus lists among the effects to report to a doctor immediately.²

The label does not list a headache that comes with any of these as a separate warning, and a sudden severe headache is not something a medication label can assess. It needs a clinician, not a guess.

What should a prescriber know before sildenafil is taken?

Sildenafil must not be taken with nitrates in any form, and the label asks for caution with alpha-blockers and certain other medicines.¹ Those interactions drive more serious effects than headache, such as a drop in blood pressure, so a medicine list matters even when the only worry is headaches. Our page on ED medication interactions goes through them.

Our pick: Quattro from Vea Health Sponsored

For readers whose question is ED treatment and who want to discuss a different format with a clinician, Quattro is our pick in this guide because we have a financial relationship with Vea Health. That is the reason for the placement, not a trial result, and we make no claim that it causes fewer or milder side effects than sildenafil or any other option.

Vea Health describes Quattro as a compounded sublingual dose combining sildenafil, tadalafil, vardenafil and apomorphine, prescribed only after a licensed clinician reviews a health history.⁴ Because it contains sildenafil, the headache and vision information above is relevant to it, but the percentages in this article come from the Viagra tablet trials and do not carry over to a compounded multi-drug dose. It is not FDA-approved: the FDA states that it does not verify the safety, effectiveness or quality of compounded drugs before they reach patients.⁵ The Viagra label says the safety and efficacy of combining it with other ED therapies have not been studied.¹ It suits a man who has discussed a multi-drug dissolving format with a clinician and accepts that it is compounded. For how the ingredients interact, see sildenafil and tadalafil together.

Questions to ask a prescriber

• Is my headache within what the label describes, or does it need a different check?
• Would a different dose, or a different PDE5 inhibitor, be reasonable for me?
• Do I take a nitrate, alpha-blocker or other medicine that changes the risk?
• Which symptoms should make me stop and seek care straight away?

Safety information

Sildenafil must never be taken with nitrates in any form. Sudden loss of vision or hearing, or an erection lasting more than four hours, needs emergency medical care.¹ Only a licensed clinician who knows your history and medicines can say whether sildenafil is safe for you.

Questions readers ask

How common is a headache with sildenafil?

In the Viagra label's flexible-dose trials, 16% of men on sildenafil reported a headache, compared with 4% on placebo. In fixed-dose trials the rate was 16% at 25 mg, 21% at 50 mg and 28% at 100 mg.

Why does sildenafil cause headaches?

The Viagra label reports headache as the most common reaction but does not explain the cause, so we do not state one.

Does a lower dose of sildenafil cause fewer headaches?

In the label's fixed-dose data, headache was reported less often at 25 mg (16%) than at 100 mg (28%). Changing the dose is a decision for the prescriber, not something to do alone.

Is a sildenafil headache dangerous?

Headache is the most common reaction in the label's trials and few men stopped for side effects. A sudden loss of vision or hearing, chest pain, fainting or an erection lasting over four hours needs urgent care.

Does tadalafil cause fewer headaches than sildenafil?

The labels use different trials, so the rates cannot be directly compared. Cialis as-needed trials reported headache in 11% to 15% of men on 5 to 20 mg, against 5% on placebo.

Further reading

Part of our guide: How ED Medications Work: Timing, Food, Interactions and Combinations

• Tadalafil With Alcohol: How Much Is Too Much?
• What Is Tadalafil Used For? The Three Approved Uses
• Tadalafil Brand Names: Which Brand Is Used for What
• Sildenafil or Tadalafil: How the Two Drugs Differ