What interacts with Cialis? Nitrates, "poppers" and riociguat must never be taken with it: together with tadalafil, the medicine in Cialis, they can make blood pressure fall dangerously. Beyond those, the Australian Cialis leaflet names a short list — some antibiotics, antifungals, HIV and seizure medicines, blood-pressure and prostate medicines, finasteride, warfarin, other erectile dysfunction medicines, grapefruit juice and large amounts of alcohol. Most call for care or a different dose rather than ruling Cialis out.
What must never be taken with Cialis?
Three things: nitrates — angina medicines such as glyceryl trinitrate, isosorbide mononitrate and sodium nitroprusside; recreational "poppers" or "amyl" (amyl and butyl nitrite); and riociguat, a medicine for high blood pressure in the lungs (Cialis CMI). The Australian product information adds nicorandil and rules out nitrates in any form, "either regularly or intermittently". The interaction outlasts a day, so in a life-threatening emergency doctors wait at least 48 hours after the last dose — 4 to 5 days in older men — before considering a nitrate (Cialis PI (Australia)): a rule for emergencies, not a schedule for alternating the two. If you are treated for a suspected heart problem, tell the ambulance staff you take Cialis (Cialis CMI). More: nitroglycerin and Viagra and is Cialis safe for heart patients?
Which medicines does the Cialis label list?
Class by class. Raising tadalafil may make side effects more likely; lowering it may make Cialis work less well (EMA — Cialis).
| Medicine | Examples named | What the labels say | In detail |
|---|---|---|---|
| Nitrates, poppers | glyceryl trinitrate, isosorbide mononitrate, nicorandil; amyl and butyl nitrite | Never together | Nitroglycerin |
| Riociguat | riociguat | Never together: may cause low blood pressure with symptoms | — |
| Antibiotics | erythromycin, clarithromycin; rifampicin | The first two are expected to raise tadalafil; rifampicin cut exposure by 88% | Antibiotics |
| Antifungals | ketoconazole, itraconazole | Ketoconazole 400 mg a day raised exposure by 312% | Same page |
| HIV medicines | ritonavir, saquinavir | Ritonavir 200 mg twice a day raised exposure by 124% | Same page |
| Seizure medicines | phenytoin, phenobarbitone, carbamazepine | Expected to lower tadalafil | — |
| Blood-pressure medicines | metoprolol, irbesartan, enalapril; amlodipine | No significant added fall in average blood pressure, though some men had larger drops | Ramipril, beta-blockers, amlodipine |
| Alpha-blockers | prazosin, doxazosin; tamsulosin, alfuzosin | Doxazosin: further falls, with fainting — "not recommended"; any alpha-blocker: lowest starting dose | Alfuzosin |
| Finasteride | finasteride | No new side effects in a trial, but no formal study: caution | — |
| Warfarin | warfarin | Clotting time unchanged; INR to be watched when tadalafil is started or stopped | Warfarin, Xarelto |
| Other ED medicines | sildenafil, for ED or for high blood pressure in the lungs | Not studied together; not to be combined | Viagra and Cialis |
| Grapefruit juice | — | Expected to raise tadalafil | Grapefruit |
| Alcohol, large amounts | — | At about 180 mL of 40% spirits for an 80 kg man, some men were dizzy on standing | Alcohol |
Sources: Cialis CMI; Cialis PI (Australia), sections 4.3–4.5; EMA — Cialis, sections 4.4–4.5.
Can you take Cialis with blood-pressure or prostate medicines?
Usually, with care. Tadalafil "may augment the blood pressure lowering effects of antihypertensive agents": in 17 men on sartans, systolic pressure fell by 30 mmHg or more in 9 on tadalafil and 5 on placebo, none with symptoms. When daily Cialis is started, the doctor may adjust the blood-pressure dose. Alpha-blockers, used for high blood pressure or an enlarged prostate — which Cialis also treats — need the most care: be stable on the alpha-blocker first and start tadalafil at the lowest dose, because together they can cause a significant drop in blood pressure. Cialis is ruled out if blood pressure is below 90/50 mmHg, or high and uncontrolled (Cialis PI (Australia)).
Which common medicines are not on the list?
Many everyday ones. In the label studies tadalafil did not add to aspirin's effect on bleeding time and changed the levels of lovastatin, a statin, only a little (Cialis PI (Australia)); no studies were done with diabetes medicines (EMA — Cialis). Ibuprofen, alprazolam (Xanax) and testosterone are not named. "Not listed" is not "tested and safe", so the prescriber should still know: aspirin, statins, ibuprofen with Cialis, Xanax with Cialis, testosterone with Cialis and metformin.
Can you take supplements with Cialis?
Tell the prescriber about every one: the Cialis leaflet asks about vitamins and supplements too (Cialis CMI). The labels name no particular vitamin and do not mention St John's wort or other herbal supplements; for herbal remedies, healthdirect's advice is to let your doctor know, "as they might interact with medicines your doctor prescribes" (healthdirect — Antidepressants). See also L-arginine with Cialis and coffee and caffeine. Some "natural" sex supplements are not what they claim: in June 2026 the TGA found undeclared tadalafil in 8 of 11 sexual enhancement products "that claimed to be dietary supplements or natural formulas", none of them on the Australian register (TGA safety advisory). Taken with Cialis, a product like that is a second dose of the same medicine.
The short answer
Never take Cialis with nitrates, poppers or riociguat. For the rest of the list, the doctor who prescribes tadalafil may change the dose or the plan, so give them your full list, supplements included. The same list for sildenafil is in can Viagra be taken with other medicines?, and both medicines side by side in our guide to taking Viagra or Cialis with other medicines.
