Adverse interactions between warfarin and nonsteroidal antiinflammatory drugs: mechanisms, clinical significance, and avoidance. Multiple drug regimens carry the risk of adverse interactions. Drugs that inhibit this enzyme, including erythromycin, cimetidine, ketoconazole and itraconazole, may increase plasma sildenafil concentrations. aspirin oral brand names and other generic formulations include:. If combination therapy is necessary, have the patient take an oral contraceptive pill with a higher estrogen content (>35 μg of ethinyl estradiol) or recommend alternative method of contraception.Avoid if possible. Conner SL. Thrombosis prevention trial: randomised trial of low-intensity oral anticoagulation with warfarin and low-dose aspirin in the primary prevention of ischaemic heart disease in men at increased risk. If combination therapy is necessary, recommend use of alternative contraceptive method during cycle.Have the patient take an oral contraceptive pill with a higher estrogen content or recommend alternative method of contraception.Prolongation of QT interval along with arrhythmias secondary to inhibited cisapride metabolismAvoid. Drugs with a narrow therapeutic range or low therapeutic index are more likely to be the objects for serious drug interactions. Bell WR. In addition, the INR should be monitored closely.Coadministration of acetylsalicylic acid (aspirin) and warfarin increases the risk of bleeding. Hirschfeld RM. The Medical Research Council's General Practice Research Framework. Singer DE. Dupuis RE. Reports of serotonin syndrome in association with tramadol and SSRI coadministration appear in the literature.At least one case report has described incoherence attributable to the combination of an SSRI and St. John's wort (extract of the Hypericum perforatum plant).A recent report documented six cases of serotonin syndrome in patients taking fluoxetine and sumatriptan (Imitrex).Another report found that the balance of documented clinical experience pertaining to the concomitant use of sumatriptan and SSRIs suggested that most patients tolerate the combination without adverse effect.Yet another report on 14 patients discovered no significant interaction between SSRIs and sumatriptan.At least one source recommends that different triptans (e.g., naratriptan [Amerge], rizatriptan [Maxalt] and zolmitriptan [Zomig]) should not be used within 24 hours of each other because of concern about the additive vasoconstrictive effects.A conservative approach would be to avoid SSRI-triptan combinations.No single method is available to enable physicians to easily avoid drug interactions in clinical practice. Gunstensen J, Sildenafil therapy should be initiated in the lowest dosage (25 mg) in patients who are also taking a cytochrome P450 3A4 inhibitor.The benefits of lowering cholesterol levels for the primary and secondary prevention of coronary artery disease have been well established. Sildenafil is primarily metabolized in the liver by cytochrome P450 3A4. Neborsky RJ. et al. Consider whether metoclopromide (Reglan) therapy is appropriate for the patient.Avoid. Consult your healthcare professional (e.g., doctor or pharmacist) for more in formation.These medications may interact and cause very harmful effects. Hirsch J. Consider whether metoclopromide (Reglan) therapy is appropriate for the patient.Avoid. Co-administration of fluoxetine and sumatriptan: the Canadian experience. Natural Medicines. Physicians' desk reference. Grapefruit. He is also an instructor in family medicine at Jefferson Medical College of Thomas Jefferson University, Philadelphia. Faul JC, Object drugs in common use include warfarin, fluoroquinolones, antiepileptic drugs, oral contraceptives, cisapride and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors. Alternative antimicrobial therapy is recommended for these patients.Some investigators advise that the hypothrombinemic response to warfarin can increase when acetaminophen is taken in a dosage of more than 2 g per day for longer than one week.One case-control study identified acetaminophen as a cause of 30 percent of INR values greater than 6.0 in patients taking warfarin.Because acetaminophen is the most frequently ingested medication in the United States, physicians should counsel warfarin-treated patients about the potential risks of a warfarin-acetaminophen interaction. Acetaminophen and warfarin: undesirable synergy [Editorial]. These problems are most likely to occur with formulations containing a low dosage of estrogen (less than 35 μg of ethinyl estradiol).The interaction between oral contraceptives and other antibiotics is controversial in that no definitive studies have demonstrated contraceptive failure from such combinations.