Meloxicam use can result in gastrointestinal toxicity and bleeding, headaches, rash, and very dark or black stool (a sign of intestinal bleeding). Like other NSAIDs , its use is associated with an increased risk of cardiovascular events such as heart attack and stroke .  It has fewer gastrointestinal side effects than diclofenac ,  piroxicam ,  naproxen ,  and perhaps all other NSAIDs which are not COX-2 selective.  Although meloxicam inhibits formation of thromboxane A, it does not appear to do so at levels that would interfere with platelet function.
Information for Pet Owners: Metacam ® (meloxicam) is a nonsteroidal anti-inflammatory drug (NSAID) and as with others in this group, side effects may occur in treated dogs. The most common adverse effects reported involve the gastrointestinal tract and usually occur within the first week of treatment. Typical symptoms include loss of appetite, vomiting, diarrhea, dark stools and depression. It is important in these situations to discontinue treatment and contact your veterinarian. In most cases, the side effects are transient and disappear after termination of treatment but in rare instances may be serious. Dogs undergoing prolonged treatment with Metacam ® should be monitored periodically. Consult your veterinarian.
Long-term administration of NSAIDs has resulted in renal papillary necrosis and other renal injury. Renal toxicity has also been seen in patients in whom renal prostaglandins have a compensatory role in the maintenance of renal perfusion. In these patients, administration of a NSAID may cause a dose-dependent reduction in prostaglandin formation and, secondarily, in renal blood flow, which may precipitate overt renal decompensation. Patients at greatest risk of this reaction are those with impaired renal function, heart failure , liver dysfunction , those taking diuretics and ACE inhibitors , and the elderly. Discontinuation of NSAID therapy is usually followed by recovery to the pretreatment state.