<p>As in the case of other NSAIDs, salicylate displaces tenoxicam from protein-binding sites and increases clearance and volume of distribution of tenoxicam. Concurrent treatment with salicylate or other NSAIDs should be avoided because of increased risk of gastrointestinal undesirable reactions. The co-administration of some NSAIDs and methotrexate has been associated with reduced renal tubular secretion of methotrexate, higher plasma concentrations of methotrexate, and severe methotrexate toxicity. Therefore, caution should be exercised when Tenoxicam is administered concurrently with methotrexate. No clinically relevant interaction was found in the small number of patients receiving concomitant treatment with gold, penicillamine or probenecid. As Tenoxicam may decrease the renal clearance of lithium, their concomitant administration may lead to increased plasma levels and toxicity of lithium. The plasma levels of lithium should be closely monitored. As with NSAIDs in general, Tenoxicam should not be administered concurrently with K-sparing diuretics. There is a known interaction between these two classes of compounds, which may cause hyperkalemia and renal failure. No clinically significant interaction between Tenoxicam and furosemide was noted, but Tenoxicam attenuates the blood pressure-lowering effect of hydrochlorothiazide. As known from other NSAIDs, Tenoxicam might attenuate the antihypertensive effects of alpha-adrenergic blockers and ACE-inhibitors. No interactions have been reported between NSAIDs and centrally-acting alpha agonists or calcium channel blockers. There was no clinically relevant interaction when Tenoxicam was administered together with atenolol. During clinical trials no interaction was reported for patients treated concomitantly with digitalis products. Thus concurrent dosing of Tenoxicam and digoxin appears to be without major risk. No interaction has been found with concomitantly administered antacids, cimetidine, warfarin and phenprocoumon at the recommended dosages. The clinical effect of oral antidiabetic drugs (glibornuride, glibenclamide, tolbutamide) was likewise not modified by Tenoxicam. Nevertheless, careful monitoring is recommended when patients concomitantly receive anticoagulants or oral antidiabetic drugs. No clinically relevant interaction has been found between Tenoxicam and low molecular weight heparin.</p>