CALMVET (meloxicam) is a member of the class of drugs known as NSAIDs (non-steroidal anti-inflammatory drugs).
CALMVET is generally given to control arthritis pain in dogs although it can be given for many other painful conditions such as injuries, cancer, surgery, dental infections, and more. In dogs, it is typically given as a once a day.
A new plane of safety for pets was made possible by new biochemical knowledge. Inflammatory biochemicals responsible for the pain and inflammation we want to allieviate are produced by an enzyme called cyclo-oxygenase 2 or simply COX-2. The goal is to inhibit this enzyme without inhibiting its counterpart cyclo-oxygenase 1. Cyclo-oxygenase 1, abbreviated COX-1, is what is called a constituitive enzyme. This means it is involved in producing regulatory biochemicals called prostaglandins that are important in maintaining the normal health and function of our bodies. We want to leave this enzyme alone. Cyclo-oxygenase 2, abbreviated COX-2, produces inflammation but also is important in regulating kidney blood flow and in some reproductive and central nervous system function. We want to inhibit COX-2 in such a way that we do not disrupt its healthful functions.
In the past, NSAIDs could not distinguish the COX enzymes and inhibited them both. With the development of COX preferential and COX selective NSAIDs, we can inhibit COX-2 and leave COX-1 alone. The introduction of COX-2 preferential NSAIDs has reduced stomach and intestinal side effects by 50% in humans and has made FDA approval of certain NSAIDs possible for pets. Meloxicam was already available for human use but human doses were way too high to be safe for most small animals.
Stomach upset: vomiting, diarrhea, and/or appetite loss are the important side effects to watch for, especially in the three weeks or so after beginning long-term meloxicam. These symptoms can have multiple meanings so it is important to sort them out.
Some pets are simply sensitive to NSAIDs despite the COX-preferential nature of meloxicam. These pets simply need nausea relief in the short term and a different pain management regimen after recovery.
Some dogs have an unrecognized liver problem. Meloxicam is removed from the body by the liver, which means that a liver on meloxicam has extra work. This is not a problem for a normal liver but a diseased liver could be tipped into failure from the extra load. This is why screening tests are so important prior to long-term use.
Another problem manifesting with upset stomach is an idiosyncratic hepatopathy (a liver condition that is not dose-dependent or predictable in any way). While this only occurs in 1 in 5,000 dogs, it is a more serious problem that likely would require hospitalization.
If a pet on meloxicam develops an upset stomach, discontinue the medication and report the problem to your veterinarian. It is prudent to check liver enzymes and kidney function (a blood test) to rule out the two liver side effect issues and kidney issues that could be seen with an upset stomach.
Other side effects typically require other pre-existing conditions that could be made worse by giving an NSAID (even a COX-preferential one). See the Concerns and Cautions section.
It is important to realize that COX-selectivity is not the sole factor in NSAID safety.
Interactions with other Drugs
Drugs of the NSAID class should not be used concurrently as the potential for the aforementioned side effects increases. For similar reasons, NSAIDS should not be used in conjunction with corticosteroid hormones such as prednisone, dexamethasone, etc. A 5 to 7 day rest period is recommended when changing from one NSAID to another. Aspirin poses an exception due to its strong platelet inactivating abilities so 10 to 14 days is recommended when switching to another veterinary NSAID from aspirin. Allow at least one week between prednisone and meloxicam.
ACE inhibitors such as enalapril, or benazepril may not be as effective when taken with meloxicam. (ACE inhibitors are used to treat hypertension or heart failure.) This is because ACE inhibitors depend on the dilation of blood vessels in the kidneys and such dilation can be interfered with by NSAIDs.)
NSAIDs also are associated with a particular idiosyncratic reaction in the liver. This reaction seems to be a canine issue only and resolves with discontinuation of the NSAID but can be life-threatening if ignored. There is no way to predict which dogs will have this reaction.
Concerns and Cautions
CALMVET works as well when given on an empty stomach as when given on a full stomach. If a patient has had some upset stomach issues with meloxicam these can often be minimized by administering the drug on a full stomach.
Maximum effect is seen approximately 8 hours after administration. When beginning a trial course of meloxicam, a response may take 3 or 4 days to show. If no response has been seen in 10 days, meloxicam has failed and a different pain medication should be tried. If one NSAID fails, another may well work.
CALMVET should not be used in pregnancy or in lactation.
As with all veterinary NSAIDs periodic monitoring tests are important to check liver enzymes and kidney function, and to generally screen the patient's health. Typically an every 6 months schedule is recommended for dogs. There is no general consensus on what is appropriate for cats but because of feline sensitivity towards NSAIDs, feline monitoring is especially important. If you are using this product in the cat, be sure you understand what monitoring schedule your veterinarian is recommending for your specific pet.
Patients being considered for long term meloxicam use should be evaluated with a complete physical examination and initial screening blood test to identify any factors, such as liver or kidney disease, that might preclude the use of this or any other NSAID.
Meloxicam should be avoided, if possible, in patients with impaired function of the liver, kidney or heart. It should also be avoided in dehydrated patients and patients with known GI ulcers.
If a patient has borderline kidney function, NSAIDs should be used with great caution or not at all as they reduce blood flow through the kidneys. It is also important that NSAIDS not be given to dehydrated patients because of this potential side effect.