[1][3] The drug is contraindicated for patients who are seniors who have been given anesthesia or surgery; are at risk of increased bleeding or kidney failure; have an active inflammatory disease involving the stomach or intestine (like ulcerative colitis); have an active stomach or intestinal ulcer; have had an acute asthmatic attack, hives, rhinitis (inflammation of the inner lining of the nasal passage), or other allergic reactions caused by aspirin or other nonsteroidal anti-inflammatory drugs (for example diclofenac, ibuprofen, indomethacin, naproxen).

[4][5] Common side effects that have been observed with tenoxicam include peptic ulceration, dyspepsia, nausea, constipation, abdominal pain, diarrhea, rash, headache, edema, renal failure, and vertigo.

[6][5][7] In rare cases, tenoxicam and other NSAIDs can contribute to thrombotic events, Stevens-Johnson Syndrome, and toxic epidermal necrolysis.

Drug types the tenoxicam may interact with include: other analgesic NSAIDs, salicylates such as aspirin, antacids, anticoagulants, cardiac glycosides, ciclosporin, quinolone antibiotics, lithium therapy, diuretics and anti-hypertensives, methotrexate, oral anti-diabetics, colestyramine, dextromethorphan, mifepristone, corticosteroids, anti-platelet agents and selective serotonin reuptake inhibitors (SSRIs), tacrolimus, zidovudine, and gold/penicillamine.

[dubious – discuss] Involved in the mechanism of action is inhibition of cyclooxygenase (COX-1 and COX-2) which leads to the potential adverse effect of increased bleeding.