Oftentimes, procedures that are routinely accomplished in companion animals with minimal restraint require sedation or anesthesia for exotic species, whether in the veterinary small animal practice, zoos or in the field.¹ The chemical immobilization of captive exotic animals involves far more control and predictability of the environment than sedating or anesthetizing the same animals in the field, but it still requires an abundance of caution and planning, as well as the requisite skills and qualified personnel. 

Although physiological responses during the maintenance of anesthesia are usually not different in a given species in the zoo versus in the field, successful induction and recovery require more knowledge and skills on the part of the veterinarian, staff and capture team (if applicable).²

While veterinarians in traditional practice settings are very well-versed in the action of commonly-used sedatives and anesthetics and the physiological responses of familiar domesticated species, it can be an ongoing challenge for some veterinarians to maintain stocks of the appropriate sedative and anesthetic drugs for exotic animals in small animal practices.

Medetomidine Hydrochloride

Medetomidine (medetomidine hydrochloride), used alone and in combination with other drugs, has been shown to be useful for the immobilization of exotic animals.³ Medetomidine is an α-2-adrenoreceptor agonist with sedative and analgesic properties. It is used by veterinarians as both a surgical anesthetic and analgesic. The pharmacological restraint and pain relief provided by medetomidine facilitates handling and aids in the conduct of diagnostic or therapeutic procedures. It also facilitates minor surgical procedures (with or without local anesthesia) and dental care where intubation is not required.

When compared to xylazine, medetomidine is reportedly 10 times more specific for alpha-2 receptors versus alpha-1 receptors. The pharmacologic effects of medetomidine include: depression of CNS (sedation, anxiolysis), GI (decreased secretions, varying effects on intestinal muscle tone) and endocrine functions, peripheral and cardiac vasoconstriction, bradycardia, respiratory depression, diuresis, hypothermia, analgesia (somatic and visceral), muscle relaxation (but not enough for intubation), and blanched or cyanotic mucous membranes. Effects on blood pressure are variable, but medetomidine can cause hypertension longer than does xylazine. Medetomidine also induces sedation for a longer period than does xylazine. Sedative effects persist longer than analgesic effects.^4,5

After IV or IM injection, onset of effect is rapid (5 minutes for IV; 10-15 minutes for IM). After SC injection, responses are unreliable and this method of administration cannot be recommended.⁴

Warnings and Contraindications

Medetomidine is contraindicated in dogs with cardiac disease, respiratory disorders, liver or kidney disease, shock, severe debilitation, or dogs stressed due to heat, cold, or fatigue.

Adverse effects reported with medetomidine use include bradycardia, occasional AV blocks, decreased respiration, hypothermia, urination, vomiting, hyperglycemia, and pain on IM injection.⁴ Rare effects have also been reported, including prolonged sedation, paradoxical excitation, hypersensitivity, apnea, and death from circulatory failure. 

The following drug interactions have either been reported or are theoretical in animals receiving medetomidine (Adapted from Plumb’s Veterinary Drugs):  

ATROPINE, GLYCOPYRROLATE: The use of atropine or glycopyrrolate to prevent or treat medetomidine-caused bradycardia is controversial as tachycardia and hypertension may result. This is more important when using higher doses of medetomidine (>20 micrograms/kg) and concomitant use is discouraged.

HYOSCINE: One study showed tachycardia and hypertension developed when hyoscine was administered IV or IM before medetomidine in horses.

OPIOIDS: Enhancement of sedation and analgesia may occur when medetomidine is used concurrently with fentanyl, butorphanol, or meperidine, but adverse effects may be pronounced as well. Reduced dosages and monitoring are advised if contemplating combination therapy.

PROPOFOL: When propofol is used after medetomidine, hypoxemia may occur. Dosage adjustments may be required along with adequate monitoring.

YOHIMBINE: May reverse the effects of medetomidine; but atipamezole is preferred for clinical use to reverse the drug’s effects.

Where to buy Medetomidine

Medetomidine is available in the U.S. through pharmaceutical manufacturers and through veterinary custom compounding companies. MEDETOMIDINE HCL 40 MG/ML INJECTABLE SOLUTION, 10ML by NexGen Pharmaceuticals is indicated for use as a sedative and analgesic to facilitate clinical examinations, clinical procedures, minor surgical procedures not requiring muscle relaxation, and minor procedures where intubation is not required.

This product carries numerous potential drug interactions. Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

¹Nielsen L. Chemical immobilization of wild and exotic animals. Iowa: Iowa State University Press, 1999; 227-281.

²Lewis JCM. Anesthesia of non-domestic cats. Hall, L.W., Taylor, P.M. Anaesthesia of the Cat. London: Bailliere Tindall, 1994; 310-349.

³Vähä-Vahe T. The clinical efficacy of medetomidine. Acta Vet Scand Suppl. 1989;85:151-3. PMID: 2571266.

⁴Plumb’s Veterinary Drugs.

⁵Di Pietro S, et al. Effects of a medetomidine-ketamine combination on Schirmer tear test I results of clinically normal cats. Am J Vet Res. 2016;77(3):310-314.