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Methocarbamol for Veterinary Use
by Barbara Forney, VMD
Methocarbamol is a centrally acting muscle-relaxant that is chemically related to guaifenesin. Methocarbamol diminishes skeletal muscle hyperactivity without altering normal muscle tone. The mechanism of action is via the internucial neurons of the spinal chord. Methocarbamol interrupts the transmission of abnormal impulses from disturbed muscle but does not affect the contractile mechanism of skeletal muscle. Methocarbamol is used to treat muscle spasms associated with back problems and exercise-related muscle problems such as exertional rhabdomyolysis. It also may be used as part of the treatment for tetanus and strychnine poisoning in dogs and cats. Methocarbamol is safe to use with nonsteroidal anti-inflammatory drugs, corticosteroids and other medications used to treat muscle spasm.
Dogs and Cats
Methocarbamol is FDA-approved for use in both dogs and cats for muscle relaxation with intervertebral disc disease and traumatic muscle-strains. It also is used to control muscle spasm and tremors in animals with tetanus or strychnine poisoning.
Injectable methocarbamol is FDA-approved for use in horses for treatment of "acute inflammatory and traumatic conditions of the skeletal muscle to reduce muscle spasm and effect striated-muscle relaxation." It frequently is used in combination with other drugs to treat exertional rhabdomyolysis. In horses that are severely tied up, especially those that are dehydrated or have discolored urine, simultaneous treatment with large volumes of intravenous fluids frequently is recommended.
Oral methocarbamol is used commonly in sport-horse practice to treat and manage sore backs and muscle strain. It sometimes is prescribed for preventive use in horses that are prone to exertional rhabdomyolysis. Methocarbamol is a CNS depressant and has secondary sedative properties that may affect coordination and performance. Although oral methocarbamol is not FDA approved for use in horses, it is used commonly and accepted practice.
Methocarbamol either is a regulated or prohibited substance in most sanctioned competition. It is an ARCI Class 4 drug. Detection times are dose related and may vary further with oral use. The USEF has issued general recommendations concerning doses and times to help competitors comply with their restrictions. USEF drug rules may be viewed on its Web site
Methocarbamol Maleate Side Effects
- Dogs and cats:
sedation, salivation, vomiting, lethargy, weakness, ataxia.
- Methocarbamol is a CNS depressant. At normal doses, it is considered a safe and relatively nontoxic drug. Salivation and staggering sometimes are seen after rapid intravenous administration. In dogs and cats, dose rate should not exceed 2 ml per minute.
- Injectable methocarbamol contains polyethylene glycol and probably should not be used in animals with decreased kidney function.
- Because methocarbamol can cause sedation and CNS depression, it may impair coordination.
- Injection-site reactions can occur after extravasation at the injection site.
Methocarbamol will cause additive CNS depression if given with other drugs that depress the central nervous system.
- Overdoses usually cause CNS depression, excessive sedation, staggering, altered reflexes and prostration.
- If the overdose was due to oral administration, gut emptying may be appropriate if the animal is conscious and the overdose was recent.
About the Author
Dr. Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania. She has a master's degree in animal science from the University of Delaware and graduated from the University of Pennsylvania School of Veterinary Medicine in 1982.
She began to develop her interest in client education and medical writing in 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.
Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.
You can purchase books by Dr. Forney at www.exclusivelyequine.com
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