Selegiline is an FDA-approved medication for dogs primarily used to manage canine cognitive dysfunction syndrome (CDS), the veterinary equivalent of dementia. Sold under the brand name Anipryl, it’s one of the few drugs specifically licensed for aging dogs experiencing mental decline. It has also been used for a certain form of Cushing’s disease, though that application is far less common today.
Canine Cognitive Dysfunction
The main reason veterinarians prescribe selegiline is cognitive dysfunction syndrome in older dogs. CDS causes behavioral changes that owners often mistake for normal aging: forgetting house training, getting “stuck” in corners, staring at walls, failing to recognize family members, sleeping all day and pacing at night, or seeming generally confused. These aren’t just quirks of getting older. They reflect real changes happening in the brain, and selegiline targets the chemistry behind them.
CDS is linked to a drop in dopamine, a brain chemical that plays a role in memory, motivation, and mental sharpness. As dogs age, dopamine levels naturally decline, and the brain accumulates damage from byproducts of normal metabolism. Selegiline works on two fronts: it blocks the enzyme (called MAO-B) that breaks down dopamine, allowing the existing supply to last longer, and it also encourages the brain to produce more dopamine in the first place. An added benefit is that by slowing dopamine breakdown, selegiline reduces the formation of free radicals, which are harmful molecules that damage brain cells over time.
Use in Cushing’s Disease
Selegiline’s other labeled use is for pituitary-dependent hyperadrenocorticism, the most common form of Cushing’s disease in dogs. In this condition, a small growth on the pituitary gland causes the body to overproduce cortisol, leading to excessive thirst, a pot-bellied appearance, hair loss, and muscle weakness. The idea behind selegiline here is that boosting dopamine helps suppress the pituitary hormone (ACTH) that drives cortisol production.
In practice, though, selegiline is rarely the first choice for Cushing’s disease. The University of Tennessee College of Veterinary Medicine lists it as “a less used alternative” treatment. Most veterinarians opt for other medications that more directly control cortisol levels, reserving selegiline for mild cases or dogs that can’t tolerate other options.
Dosing and What to Expect
For cognitive dysfunction, the standard dose is 0.5 to 1 mg/kg given by mouth once daily, preferably in the morning. Morning dosing matters because selegiline can have a mildly stimulating effect, and giving it later in the day could disrupt your dog’s sleep cycle.
Improvement isn’t immediate. The American Animal Hospital Association’s 2023 senior care guidelines recommend giving selegiline at the starting dose for a full 30 days before deciding whether it’s working. If you haven’t noticed any change after that first month, your vet may increase the dose to the next tablet size. Some dogs show noticeable improvement within the first few weeks, while others take longer. The changes can be subtle at first: your dog might seem a little more “present,” navigate the house more confidently, or sleep better at night.
Selegiline doesn’t cure CDS. It manages symptoms and may slow progression, but the underlying brain changes continue over time. Many owners find it gives their dog a meaningful improvement in quality of life for months to years.
Side Effects
Selegiline is generally well tolerated. The most commonly reported side effects are mild and include vomiting, diarrhea, decreased appetite, and restlessness. Some dogs become more active or slightly agitated, particularly when first starting the medication. These effects often settle within the first week or two.
Serious side effects are uncommon at the recommended dose. However, one critical risk to know about is serotonin syndrome, which can occur if selegiline is combined with certain other medications (more on that below). Signs of serotonin syndrome include rapid heart rate, muscle tremors or rigidity, pacing, disorientation, vomiting, diarrhea, and in severe cases, seizures. These signs can appear within one to two hours of a problematic drug combination, or develop over several days with ongoing dosing.
Dangerous Drug Interactions
This is the most important safety concern with selegiline. Because it affects how the brain processes certain chemicals, combining it with other drugs that raise serotonin or stimulate the nervous system can trigger life-threatening reactions.
- Antidepressants and anti-anxiety medications. SSRIs (like fluoxetine, commonly prescribed for dog anxiety) and tricyclic antidepressants must not be used alongside selegiline. The combination can cause serotonin syndrome. A washout period of at least two weeks is typically needed when switching between these drugs.
- Certain decongestants and stimulants. The manufacturer specifically warns against combining selegiline with ephedrine and similar compounds. In humans, combining MAO inhibitors with these types of drugs has triggered dangerous spikes in blood pressure.
- Opioid pain medications. Some opioids interact with MAO inhibitors and should be avoided or used with extreme caution.
If your dog is on any other medication, including supplements, make sure your vet knows before starting selegiline. This is especially relevant for dogs already taking something for anxiety or behavioral issues, since the overlap in drug types creates the highest risk.
Is Selegiline Right for Your Dog?
Selegiline works best for dogs with mild to moderate cognitive dysfunction. If your senior dog has started showing signs of confusion, disrupted sleep patterns, or personality changes, it’s worth discussing with your vet. The earlier CDS is addressed, the more room there is to see improvement. Dogs with advanced cognitive decline may still benefit, but the gains tend to be smaller.
For Cushing’s disease, selegiline is an option but not the standard. If your vet has diagnosed pituitary-dependent Cushing’s and recommends selegiline, it’s likely because your dog’s case is mild or because other treatments haven’t been a good fit.
The medication is given long-term in both cases. Stopping it abruptly isn’t dangerous, but the symptoms it was managing will return. Most dogs stay on selegiline for the remainder of their lives once they’ve started, with periodic vet check-ins to assess whether the dose still makes sense and whether the drug is still providing benefit.