Can you take Viagra with blood thinners or warfarin? Usually yes — no interaction with warfarin was found. In the studies behind the label, sildenafil had no significant interaction with warfarin and did not add to aspirin's effect on bleeding time; tadalafil (Cialis) did not change warfarin's effect on clotting either. What needs care is a bleeding problem itself, so the doctor who prescribes Viagra must know you take a blood thinner.
Does Viagra interact with warfarin?
No significant interaction was found. The European product information states that "no significant interactions were shown when sildenafil (50 mg) was co-administered with tolbutamide (250 mg) or warfarin (40 mg)" (EMA, Viagra). For tadalafil, the Cialis product information says it had no clinically significant effect on warfarin levels "nor did tadalafil affect changes in prothrombin time induced by warfarin" (EMA, Cialis).
What about aspirin and other antiplatelet medicines?
Sildenafil 50 mg did not add to the increase in bleeding time caused by aspirin, and tadalafil 10 and 20 mg did not either (EMA labels). The full answer is in can aspirin be taken with Viagra?
What about the newer blood thinners, such as Xarelto?
Neither label names rivaroxaban (Xarelto), apixaban or dabigatran. "Not named" is not the same as "tested", so these need the same care as any combination: tell the prescriber. The Xarelto question has its own page — can Xarelto be taken with Viagra or Cialis?
When is more care needed?
When there is a bleeding disorder or an active stomach ulcer. The sildenafil label notes there is no safety information for these patients, so it should be given to them "only after careful benefit-risk assessment" (EMA, Viagra). Men on blood thinners usually take them because of a heart or blood-vessel condition — and that condition, more than the blood thinner, is what the doctor weighs before prescribing an ED medicine.
What must never be combined with Viagra?
Nitrates — medicines for angina, including sprays or tablets for chest pain — because together they can cause a sudden, dangerous drop in blood pressure (healthdirect). Many men on blood thinners also have a nitrate spray for chest pain; if you do, Viagra is not for you. More in can nitrates be taken with Viagra?
What side effects should you watch for?
Unusual bleeding or bruising is a reason to call your doctor whatever you take. The common side effects of ED medicines are headache, facial flushing, a blocked nose and indigestion; an erection lasting more than 4 hours needs the nearest hospital emergency department (healthdirect).
The short answer
Viagra and Cialis showed no interaction with warfarin or aspirin in their labels' studies; the newer blood thinners are simply not named. A bleeding disorder, an ulcer or a nitrate for chest pain changes the answer, so tell the prescriber everything you take. Every combination is covered in our guide to taking Viagra or Cialis with other medicines.
