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Unfortunately, as dogs get older, they can experience changes to their health and mental faculties. Some senior dogs show signs of cognitive impairment akin to human Alzheimer鈥檚 disease. This condition, known as cognitive dysfunction syndrome in dogs, causes issues such as , restlessness or lethargy, pooping or peeing in the house, and .
Senior dogs can also develop tumors in their pituitary glands, or occasionally their adrenal glands, which leads to excess production of the hormone cortisol. This condition is known as Cushing鈥檚 disease, and early signs include excessive thirst and frequent urination. As the illness progresses, you may see weakness, loss of muscle mass, skin lesions, hair loss, obesity, and a lack of energy.
If your dog is exhibiting signs of any of these health conditions, discuss them with your veterinarian. After considering all diagnostic result options, your veterinarian might prescribe a drug called , also known by the brand name . Read on to learn about the correct use of selegiline, how it helps, potential side effects, and alternatives.
What Is Selegiline Used for in Dogs?
According to veterinary psychiatrist and certified veterinary behaviorist , DVM, Diplomate of the American College of Veterinary Behavior, selegiline is only used in North America for dogs with Cushing鈥檚 disease or cognitive decline. It鈥檚 licensed for use in Europe for chronic emotional disorders. However, monoamine oxidase inhibitors (MAO inhibitor), the class of drug selegiline belongs to, fell out of favor for emotional disorders when newer, more effective medications entered the market.
How Selegiline Works in a Dog鈥檚 Brain
Like a human鈥檚 brain, a dog鈥檚 brain uses neurotransmitters to communicate between nerves. One of these neurotransmitters is called dopamine, and it鈥檚 essential for memory function among other things. To prevent neurotransmitters from accumulating, the brain also has enzymes that break them down. One of these enzymes is monoamine oxidase, which gets rid of dopamine.
Selegiline works by inhibiting monoamine oxidase, allowing dopamine to stay in the brain longer. In the case of Cushing鈥檚 disease, dopamine regulates and inhibits the production of a stimulatory hormone called adrenocorticotrophic hormone (ACTH). ACTH can lead to the adrenal glands overproducing cortisol, which causes the symptoms of Cushing鈥檚 disease. Therefore, selegiline minimizes the effects of ACTH by helping keep dopamine around.
Cognitive impairment is associated with a drop in dopamine. So, by using selegiline and allowing dopamine to linger in the brain, there may be an improvement in cognitive dysfunction symptoms. In addition, Dr. Denenberg explains, 鈥淪elegiline enhances the activity of other enzymes, such as superoxide dismutase and superoxide catalase. These enzymes inhibit and degrade the brain鈥檚 toxic oxygen molecules (toxic free radicals). These toxic molecules cause oxidative damage inside neurons (burning the cell in lay terms), leading to brain tissue loss.鈥�
Benefits of Selegiline
For dogs with Cushing鈥檚 disease, selegiline is only of benefit if the dog鈥檚 tumor is in the section of the pituitary gland where ACTH is dependent on dopamine. If the tumor is in another part of the pituitary gland, the medication will do nothing more than provide a general stimulatory effect.
In the case of cognitive dysfunction syndrome in dogs, Dr. Denenberg says studies have shown that selegiline helps improve memory and learning, both in the lab and in clinical settings. Dogs were tested in a variety of ways including remembering the location of food, learning to identify markers of food, and remembering where food was hidden. The dogs that were given selegiline performed better than those dogs that were given a placebo. However, he warns, 鈥淚t is important to remember that the level of 鈥榮uccess鈥� of using this medication is limited. It will not cure cognitive decline; it will only slow it and may cause some improvement.鈥�
How to Administer Selegiline
Selegiline is given to your dog as a daily tablet. Since it鈥檚 a stimulant, so Dr. Denenberg advises administering selegiline in the morning. If you give it to your dog in the evening, your dog might be awake and alert through the night. He also says patience is a must with this medication, as it can take about four to six weeks to see if it鈥檒l be helpful for your dog.
Your veterinarian will probably start at a low dose and increase it if needed. Missing one dose isn鈥檛 likely to cause any drop in effect as the level of dopamine will remain constant in your dog鈥檚 brain. However, a missed dose can impact your dog鈥檚 alertness and lead to restlessness and irritability.
Side Effects and Alternative Medications
When first starting your dog on selegiline, you may notice irritability and restlessness. The drug can also cause an upset stomach, and, in rare cases, reduced hearing. It鈥檚 also important you don鈥檛 feed your dog any hard cheeses or cured meats while they鈥檙e on selegiline, as the medication also affects the monoamine oxidase enzyme in the gastrointestinal tract. Dr. Denenberg says the likelihood of a reaction is low, since most dogs don鈥檛 get a lot of these foods. But the reaction can be fatal in humans on MOA inhibitors, so it鈥檚 best to practice caution.
In addition, selegiline shouldn鈥檛 be used with other drugs that impact serotonin, another brain neurotransmitter, such as SSRI鈥檚 or tricyclic antidepressants including Elavil and Prozac. Otherwise, your dog could potentially suffer serotonin syndrome, which is caused by excess serotonin in the body, leading to symptoms such as diarrhea, vomiting, decreased appetite, elevated heart rate, panting, pacing, and seizures.
If selegiline isn鈥檛 effective for your dog, there are other medications that increase dopamine, such as cabergoline and bromocriptine. But Dr. Denenberg says while they can be used, they鈥檙e neither licensed for this purpose nor as effective. For Cushing鈥檚 disease in particular, there are better alternatives to selegiline, such as the medications (brand name ) and (brand name ). These drugs selectively destroy part of the outer section of the adrenal gland, so even though the pituitary gland tumor continues to release ACTH, the cortisol levels will remain normal.
For dogs with cognitive dysfunction syndrome, natural supplements can be helpful. Dr. Denenberg says , ginkgo biloba, apoaequorin, and can all support brain function and reduce the levels of toxic free radicals in the brain. However, their efficacy hasn鈥檛 been proven to the same degree as prescription medications. In addition, prescription diets such as and are licensed for cognitive decline in dogs and can help manage the condition.
This article is intended solely as general guidance, and does not constitute health or other professional advice. Individual situations and applicable laws vary by jurisdiction, and you are encouraged to obtain appropriate advice from qualified professionals in the applicable jurisdictions. We make no representations or warranties concerning any course of action taken by any person following or otherwise using the information offered or provided in this article, including any such information associated with and provided in connection with third-party products, and we will not be liable for any direct, indirect, consequential, special, exemplary or other damages that may result, including but not limited to economic loss, injury, illness or death.