Selegiline in Dogs

Selegiline is a drug belonging to the group of inhibitors of the enzyme monoamine oxidase type B (MAO-B), which has the following effects:

• By selectively inhibiting the enzyme MAO-B in the brain, it manages to increase the levels of dopamine and other catecholamines in the cerebral cortex and hippocampus, which is deficient in patients with dementia.
• It has a mild antidepressant effect .
• It suppresses the oxidative effect associated with dopamine and reduces the load of free radicals, which gives it a neuroprotective effect .

Currently, selegiline is only marketed as tablets for use in people . However, veterinary professionals can also prescribe this drug using the so-called «cascade prescription», which consists of prescribing a drug that is not authorized for a specific animal species when there is a therapeutic gap.

Selegiline is used for the treatment of cognitive dysfunction syndrome in the geriatric dog. Cognitive Dysfunction Syndrome (SCD) is a degenerative disease similar to Alzheimer’s disease in people, which affects geriatric dogs and produces a wide variety of behavioral disturbances. Although the mechanism by which selegiline induces improvement in dogs with CDS is not precisely understood, it is believed to be due to an increase in dopamine and other catecholamines in the cerebral cortex and hippocampus.

It is worth mentioning that the use of selegiline in the treatment of canine Cushing’s syndrome of pituitary origin has been studied. Selegiline produces an increase in dopamine levels, which is capable of inhibiting the exacerbated production of ACTH that occurs during pituitary cushing. The results of these studies discourage the use of selegiline as the only treatment for pituitary cushing’s due to its low efficacy. However, it may be advisable to use selegiline in combination with other drugs (such as trilostane) as it appears to improve activity level and quality of life in dogs with pituitary cushing’s.

The dose of 0.5 mg per kg of body weight per day has been shown to be effective in improving short-term memory, reducing signs of cognitive dysfunction and increasing longevity in elderly dogs with cognitive dysfunction syndrome. Likewise, the administration of selegiline for dogs in the morning is recommended , especially in dogs with cognitive dysfunction syndrome that present alterations in the sleep/wake cycle.

Response to therapy may be evident within a few days, although most caregivers notice improvement within the first two weeks of treatment.

At the recommended dose, side effects have been reported in a small number of treated patients . However, as in any pharmacological treatment, it is important to attend to the possible appearance of adverse effects and go to the veterinarian if they occur.

In the specific case of selegiline in dogs, the possible side effects that can be observed are:

• high blood pressure
• Sedation or excitement , depending on the patient.
• Serotonergic syndrome : the inhibition of the monoamine oxidase enzyme prevents many of the enzymes present in food from being metabolized, which can activate serotonin receptors and produce this syndrome, characterized by hyperthermia, muscular rigidity, tremors, gastrointestinal signs, etc.
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Although selegiline is a drug that is licensed for veterinary use, there are some situations in which its use can be counterproductive. Next, we collect the main contraindications of selegiline in dogs:

• Allergy or hypersensitivity to selegiline or to any of the excipients that accompany the active ingredient
• Gastric or duodenal ulcers .
• Dogs under treatment with tricyclic antidepressants, serotonin reuptake inhibitors (such as fluoxetine), serotonin and norepinephrine reuptake inhibitors (such as venlafaxine), sympathomimetics, monoamine oxidase inhibitors and/or opioids.

For all of the above, it is very important to administer selegiline in dogs under veterinary supervision, we should never self-medicate our dog because we could worsen his situation.