Can you take Viagra with an antibiotic? Usually yes — it depends on which antibiotic. Most common antibiotics, amoxicillin among them, are not named on the Viagra or Cialis labels, and azithromycin had no effect on sildenafil in a study. The ones that matter are erythromycin and clarithromycin, which raise the level of sildenafil and tadalafil in the blood, and rifampicin, which lowers it; with any of these, the doctor who prescribes your erectile dysfunction medicine may need to change the dose.
Which antibiotics interact with Viagra?
Erythromycin and rifampicin are the two the Australian Viagra leaflet names, under "some antibiotics" (Viagra CMI). The Cialis leaflet names rifampicin, erythromycin and clarithromycin (Cialis CMI). The antibiotics' own leaflets agree: the Australian leaflet for clarithromycin lists "sildenafil, tadalafil, vardenafil (used to treat erectile dysfunction in adult males)" among the medicines it may affect (Klacid CMI), and the one for erythromycin lists sildenafil (E-Mycin CMI). Both are macrolide antibiotics; clarithromycin is used for chest, throat, ear and skin infections, among others (Klacid CMI). In short, certain antibiotics can increase the levels of Viagra in your blood, and one can lower them.
What happens if you take Viagra with erythromycin or clarithromycin?
More sildenafil stays in your blood. In a study, erythromycin taken twice a day for 5 days raised the exposure to a single 100 mg dose of sildenafil by 182%. In men already taking medicines of this kind, which slow the enzyme that breaks sildenafil down (CYP3A4), no increase in side effects was seen — but the label still says a starting dose of 25 mg should be considered (EMA — Viagra). The tadalafil label says erythromycin and clarithromycin "should be co-administered with caution" because they would be expected to raise tadalafil levels, so its side effects "might be increased" (EMA — Cialis). The side effects to expect are the usual ones — headache, flushing, a blocked nose, indigestion (healthdirect — ED medicines); an erection lasting more than 4 hours needs the nearest hospital emergency department (healthdirect — Sildenafil).
Can you take Viagra with amoxicillin, penicillin or doxycycline?
None of them is named. Amoxicillin and the other penicillins, doxycycline and ciprofloxacin do not appear in the interaction sections of the Viagra or Cialis leaflets or of the European product information for either medicine. Amoxicillin, the most-asked pairing, has its own page: can amoxicillin and Viagra be taken together? "Not named" means no interaction is known, not that the pair was studied, so tell the doctor who prescribes the antibiotic that you take Viagra — the Viagra leaflet asks you to tell any other doctor, dentist or pharmacist treating you (Viagra CMI).
Is azithromycin safe with Viagra or Cialis?
No interaction was found with sildenafil. Azithromycin is a macrolide, like erythromycin and clarithromycin (Klacid CMI), but in healthy men azithromycin 500 mg a day for 3 days had no effect on sildenafil's blood levels or half-life (EMA — Viagra). Azithromycin is not on the Cialis leaflet's list either (Cialis CMI).
Can rifampicin stop Viagra or Cialis working?
It can make them weaker. Rifampicin, an antibiotic used for some infections, speeds up the breakdown of both medicines: it cut tadalafil exposure by 88%, which "can be anticipated to decrease the efficacy of tadalafil", by an amount that is not known (EMA — Cialis). The sildenafil label expects strong inducers of the same enzyme, such as rifampicin, to lower sildenafil levels too (EMA — Viagra). If your ED tablet seems to stop working on a course of rifampicin, tell your doctor rather than taking more — one sildenafil tablet in 24 hours is the limit (healthdirect — Sildenafil).
Are antifungals and HIV medicines the same problem?
Yes, and a bigger one. Ketoconazole and itraconazole are antifungals, not antibiotics, and they slow the same enzyme more strongly; ketoconazole raised tadalafil exposure up to fourfold (EMA — Cialis). The HIV medicine ritonavir raised sildenafil exposure elevenfold, so the two are not advised together, and sildenafil should never exceed 25 mg in 48 hours alongside it (EMA — Viagra). The full Cialis list is in Cialis interactions with other medicines and supplements, and the Viagra one in what medicines should not be taken with Viagra?
Do you need to space the doses apart?
No label says so. What the labels ask for is a lower starting dose of sildenafil with erythromycin and similar medicines, and caution with tadalafil — decisions for the prescriber, who can only make them if they know about both medicines. The Viagra leaflet asks you to tell your doctor and pharmacist before starting any new medicine (Viagra CMI).
The short answer
Most antibiotics, including amoxicillin and azithromycin, are not a known problem with Viagra or Cialis. Erythromycin and clarithromycin raise the level of both, and rifampicin lowers it, so with those the dose may need changing. Nitrates for chest pain are never allowed with either (why nitrates and Viagra never mix). Every other combination is covered in our guide to taking Viagra or Cialis with other medicines.
