Increased risk of bleeding due to potential additive effect w/ oral anticoagulants, glycoprotein IIb/IIIa inhibitors, heparin, thrombolytics, NSAIDs including COX-2 inhibitors, SSRIs. Increased occult GI blood loss w/ concomitant administration of clopidogrel & naproxen. Reduced effect of ASA w/ metamizole. Potential delayed & reduced absorption of clopidogrel w/ opioid agonists. Clopidogrel: Increased levels of the active metabolite w/ strong CYP2C19 inducers (eg, rifampicin). Reduced levels of the active metabolite w/ strong or moderate CYP2C19 inhibitors (eg, omeprazole, esomeprazole, fluvoxamine, fluoxetine, moclobemide, voriconazole, fluconazole, ticlopidine, carbamazepine, efavirenz). Decreased exposure of the active metabolite w/ PPIs eg, omeprazole, esomeprazole. Reduced platelet inhibition in HIV patients treated w/ ritonavir- or cobicistat-boosted anti-retroviral therapy. Increased exposure of CYP2C8 substrates eg, repaglinide & paclitaxel. ASA: May inhibit the effect of uricosurics (eg, benzbromarone, probenecid, sulfinpyrazone). Can inhibit renal clearance of MTX. Increased risk of renal failure w/ tenofovir disoproxil fumarate. Increased serum levels of total & free valproic acid. Risk of Reye's syndrome w/ varicella vaccine. Do not give salicylates for an interval of 6 wk after receiving varicella vaccine. Increased risk of metabolic acidosis w/ acetazolamide. Increased risk of GI ulceration, perforation & haemorrhage w/ nicorandil. Increased risk of GI injury w/ alcohol.