Can people with epilepsy safely take Viagra or Cialis? Usually, yes: epilepsy is not one of the conditions their labels rule out. Two cautions apply. Seizures are listed as a rare event reported after these medicines went on sale, without proof that the tablet caused them. And some seizure medicines — carbamazepine, phenytoin and phenobarbitone — speed up the breakdown of tadalafil (Cialis), so it may work less well. Tell the doctor who prescribes an ED medicine about your epilepsy and every medicine you take for it.
Is epilepsy a reason not to take Viagra or Cialis?
No. The sildenafil label rules it out with nitrates or riociguat, severe heart disease, severe liver disease, low blood pressure, a recent stroke or heart attack, past vision loss from NAION and inherited retinal disease — not with epilepsy (EMA — Viagra). Neither Australian leaflet names epilepsy among its reasons not to take the medicine (Viagra CMI; Cialis CMI), though the Viagra leaflet asks you to mention any other medical condition before you start.
Can Viagra or Cialis cause a seizure?
Rarely, a seizure has been reported; whether the medicine caused it is not known. The European sildenafil label lists seizure, and a seizure returning in someone who has had them before, as rare — up to 1 man in 1,000 — and reported only after marketing (EMA — Viagra). The Australian product information lists "seizure, seizure recurrence and anxiety" among events "observed in temporal association with VIAGRA" (Viagra PI (Australia)). For tadalafil, seizures are a post-marketing report of unknown frequency in the Australian product information (Cialis PI (Australia)) and rare in the European label, never seen in its placebo-controlled trials (EMA — Cialis). The Cialis leaflet says "It is not possible to determine whether these events are related directly to CIALIS, to other diseases or medications, to other factors, or to a combination of factors" (Cialis CMI).
What does the research show?
Case reports and animal studies — no trials in men with epilepsy. Doctors in Israel described tonic-clonic seizures in patients taking sildenafil (Gilad et al., 2002). A review found case reports of seizures in men without epilepsy after sildenafil, tadalafil or vardenafil, and animal studies suggesting these medicines make seizures easier to set off; it noted that few studies have looked at treating erectile dysfunction in men with epilepsy (Matos et al., 2012). In rats, both sildenafil and tadalafil lowered the seizure threshold (Silva et al., 2023). None of this measures the risk for a man whose seizures are controlled.
Do epilepsy medicines interact with Viagra or Cialis?
Some weaken Cialis; neither ED medicine is expected to change epilepsy medicine levels. The Cialis leaflet names "some medicines used to treat seizures such as phenytoin, phenobarbitone and carbamazepine" among those that may interfere with it (Cialis CMI). They speed up the enzyme that breaks tadalafil down: rifampicin, which works the same way, cut tadalafil levels by 88%, and "It can be expected that concomitant administration of other CYP3A4 inducers such as phenobarbitone, phenytoin and carbamazepine would also decrease plasma concentrations of tadalafil" (Cialis PI). For sildenafil the picture is mixed: its label expects strong inducers such as rifampicin to lower its levels, but in an analysis of its trial data, men taking barbiturates showed no change (Viagra PI), and seizure medicines are not on the Viagra leaflet's interaction list (Viagra CMI). Some HIV medicines do the opposite — see can HIV patients take Viagra? In the other direction, sildenafil is "unlikely" to alter the clearance of medicines broken down by the same enzymes (EMA — Viagra), and tadalafil does not speed up or slow down these enzymes (EMA — Cialis).
Can epilepsy or its medicines cause erection problems?
Yes, often. "Nearly one-half of men and women with epilepsy have sexual dysfunction", in men mostly erectile dysfunction and premature ejaculation; it is more likely with uncontrolled or long-standing epilepsy, frequent seizures and "enzyme-inducing and multiple" seizure medicines, while limited data suggest oxcarbazepine, lamotrigine and levetiracetam cause little or none. Depression and anxiety add to it (Rathore et al., 2019). Gabapentin, used for epilepsy and nerve pain, has its own page: does gabapentin cause erectile dysfunction? Never stop or skip an epilepsy medicine to fix your erections — missing a dose is a seizure trigger (healthdirect — Epilepsy); a change of medicine is a decision for your neurologist.
What should you do if you have a seizure after taking one?
Get medical help. The Viagra leaflet says to call your doctor straight away or go to the nearest emergency department for "seizures, fits or convulsions" (Viagra CMI); the Cialis leaflet says to stop taking it and contact a doctor immediately (Cialis CMI). For anyone having a seizure, call triple zero (000) for an ambulance if it lasts more than 5 minutes or the person does not regain consciousness (healthdirect — Epilepsy).
The short answer
Epilepsy does not rule out Viagra or Cialis. Seizures are a rare reported event, enzyme-inducing seizure medicines such as carbamazepine can make tadalafil less effective, and your prescriber needs the full list of what you take. Parkinson's disease, another nerve condition, is covered in can Viagra be used with Parkinson's disease?; other situations are in our guide to Viagra and Cialis with special conditions.
