Canine selegiline (Anipryl) drug guide — labeled indications for dog dementia (CDS) and Cushing's, dosage, side effects, openFDA data, and critical MAOI drug interactions.

Selegiline hydrochloride (brand name Anipryl) is a monoamine oxidase inhibitor (MAOI) that holds a unique position in veterinary pharmacology. It is the only FDA-approved veterinary drug for the treatment of canine cognitive dysfunction syndrome (CDS)—often referred to as "dog dementia"—and is also labeled for controlling the clinical signs associated with pituitary-dependent hyperadrenocorticism (Cushing's disease).

Because selegiline acts on central neurotransmitter pathways, using it safely requires a solid understanding of its mechanism of action, its clinical expectations, and its potential drug interactions. As a monoamine oxidase inhibitor, selegiline cannot be combined with several common veterinary medications—such as behavioral drugs or certain analgesics—without risking a severe, potentially life-threatening reaction known as serotonin syndrome. This guide provides a detailed analysis of selegiline's dual indications, dosing protocols, real-world adverse-event profile, and the critical drug safety rules that govern its use.

Quick answer

Selegiline (Anipryl) is an FDA-approved veterinary monoamine oxidase B (MAO-B) inhibitor labeled for two indications in dogs: canine cognitive dysfunction (CDS) and pituitary-dependent Cushing's disease (when clinical signs persist and standard therapies like trilostane are not tolerated). The standard starting dose is 0.5 to 1.0 mg/kg orally once daily in the morning, titrating up to a maximum of 2.0 mg/kg daily after 4 to 6 weeks if response is insufficient.

Because selegiline is an MAOI, its most critical safety warning is the risk of serotonin syndrome if combined with selective serotonin reuptake inhibitors (SSRIs like fluoxetine/[Reconcile]), tricyclic antidepressants (TCAs like clomipramine/[Clomicalm]), other MAOIs, or certain opioids (like tramadol). A strict washout window of at least 14 days is required when switching between these drugs (and up to 5–6 weeks if switching from fluoxetine).

Real-world pharmacovigilance data from the openFDA veterinary adverse event database (4,504 unique selegiline reports, including 4,117 canine cases) corroborates the drug's labeled profile, with vomiting (456 reports), diarrhea (340 reports), anorexia (327 reports), and restlessness (263 reports) as the most common side effects. The data also reveals a high volume of "lack of efficacy" reports (441 for cognitive dysfunction, 252 for Cushing's), emphasizing that selegiline is not a cure, and clinical response in older, geriatric patients is often partial and variable.

What is selegiline (Anipryl), and what is it used for in dogs?

Selegiline hydrochloride (also known as L-deprenyl) is a phenethylamine derivative. In the brain, monoamine oxidase (MAO) enzymes are responsible for breaking down monoamine neurotransmitters, including dopamine, serotonin, norepinephrine, and epinephrine. MAO exists in two primary isoforms:

Monoamine Oxidase A (MAO-A): Primarily breaks down serotonin, norepinephrine, and melatonin.
Monoamine Oxidase B (MAO-B): Primarily breaks down dopamine and phenethylamine.

At labeled veterinary dosages (0.5 to 1.0 mg/kg once daily), selegiline is a selective, irreversible inhibitor of MAO-B. By binding to and inactivating MAO-B, selegiline prevents the breakdown of dopamine in the synaptic cleft, leading to increased dopamine concentrations in the central nervous system.

Dopamine is a critical neurotransmitter for regulating motor function, cognitive processes, motivation, and reward pathways. By enhancing dopaminergic transmission, selegiline helps offset the age-related decline in dopamine levels observed in geriatric dogs.

Additionally, selegiline's neuroprotective effects are enhanced by secondary mechanisms:

Reduction of Free Radicals: The breakdown of dopamine by MAO-B produces hydrogen peroxide, which contributes to oxidative stress and cell death in the brain. Inhibiting MAO-B reduces the production of these damaging reactive oxygen species.
Active Metabolites: In the liver, selegiline is metabolized into L-amphetamine and L-methamphetamine. While these metabolites are the less active "L" optical isomers (which have significantly less cardiovascular and stimulatory effects than the "D" isomers), they still provide mild central nervous system stimulation and promote dopamine release.
Enhancement of Neurotrophic Factors: Selegiline has been shown to increase the expression of brain-derived neurotrophic factor (BDNF) and other survival signals in nervous tissue.

Importantly, selegiline's selectivity for MAO-B is dose-dependent. If the dose is escalated above the recommended range (exceeding 2.0 mg/kg/day), selegiline loses its selectivity and begins to inhibit MAO-A as well. This increases the risk of systemic side effects, such as hypertension and serotonin syndrome.

How does selegiline fit canine cognitive dysfunction (dog dementia)?

Canine Cognitive Dysfunction (CDS) is a progressive neurodegenerative disease of senior dogs that shares striking pathologic similarities with Alzheimer's disease in humans. The brains of dogs with CDS show:

Accumulation of neurotoxic beta-amyloid plaques in the cerebral cortex and hippocampus.
Chronic cerebral amyloid angiopathy, which reduces blood flow and oxygen delivery to brain tissue.
Microscopic hemorrhages, loss of myelin, and generalized brain atrophy.
Systemic depletion of critical neurotransmitters, particularly dopamine and acetylcholine.

Clinically, CDS manifests as a predictable constellation of behavioral changes that can be staged using diagnostic frameworks such as the DISHAA scale, which evaluates:

D - Disorientation: Wandering aimlessly, getting stuck behind doors or in corners, failing to recognize familiar people or places.
I - Interactions: Altered social behavior, such as becoming unusually clingy or withdrawing from family interactions.
S - Sleep-Wake Cycles: Waking up and pacing or vocalizing at night, sleeping more during the day.
H - House-soiling: Losing voluntary bladder or bowel control in a previously house-trained dog.
A - Activity: Decreased purposeful activity, or the development of repetitive, purposeless actions (e.g., pacing in circles).
A - Anxiety: Increased sensitivity to noise, separation anxiety, or generalized fearfulness.

Understanding how selegiline fits into this syndrome requires consulting our guide to canine cognitive dysfunction (Dishaa stages). Selegiline is typically initiated during the mild-to-moderate window of canine cognitive dysfunction — the optimal therapeutic intervention stage in the Dishaa framework — once a dog is showing active DISHAA signs but still retains a functional quality of life.

By increasing dopamine levels in the cerebral cortex and striatum, selegiline improves cognitive function, enhances alertness, and helps restore normal sleep-wake cycles. However, veterinary teams must counsel owners that selegiline is not a cure for CDS. It does not halt the underlying deposition of beta-amyloid or brain atrophy. Instead, it manages the chemical deficiency caused by the degeneration, providing a period of improved cognitive function and quality of life.

How and when is selegiline used for pituitary-dependent Cushing's disease?

Selegiline's second FDA-approved indication is for controlling the clinical signs of pituitary-dependent hyperadrenocorticism (PDH), or Cushing's disease. To understand this use, it is necessary to review our guide to Cushing's disease testing and trilostane monitoring.

In a healthy dog, the hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to secrete adrenocorticotropic hormone (ACTH), which in turn stimulates the adrenal cortex to produce cortisol. Cortisol provides negative feedback to both the hypothalamus and pituitary, keeping the system in balance.

Crucially, dopamine acts as a natural inhibitor of ACTH secretion in the pituitary gland, particularly in the pars intermedia. In dogs with pituitary-dependent Cushing's disease (which is caused by a benign pituitary tumor), there is often a progressive loss of dopaminergic inhibition, allowing the pituitary to secrete excess ACTH.

                   [HYPOTHALAMIC-PITUITARY-ADRENAL PATHWAY]

                   Hypothalamus  
                        |
                        | (CRH)
                        v
                 Pituitary Gland  <--- [Dopamine Inhibits ACTH]
                        |               (Enhanced by Selegiline)
                        | (ACTH)
                        v
                  Adrenal Gland
                        |
                        | (Cortisol)
                        v
                  Clinical Signs
             (Polyuria, Polydipsia, Alopecia)

By inhibiting MAO-B and increasing dopamine concentrations in the pituitary gland, selegiline aims to restore this feedback loop, thereby reducing ACTH secretion and lowering circulating cortisol levels.

Positioning Selegiline in Cushing's Treatment

Despite its FDA approval, selegiline is rarely used as a first-line treatment for canine Cushing's disease. The primary reasons include:

Variable Efficacy: Studies have shown that only approximately 20% to 40% of dogs with PDH show a clinical response to selegiline. This is because many pituitary tumors arise from the pars distalis (which is less sensitive to dopaminergic inhibition) rather than the pars intermedia.
Trilostane Dominance: Trilostane (Vetoryl) directly inhibits the synthesis of cortisol in the adrenal gland and has a much higher success rate (> 80–90%).

Therefore, selegiline is positioned as an alternative treatment for Cushing's in specific scenarios:

Trilostane/Mitotane Intolerance: For dogs that experience severe side effects or adrenal crises from cortisol-inhibiting drugs.
Mild Clinical Signs: In older dogs with very mild signs of Cushing's where the owner wants a milder therapy.
Concurrent Cognitive Decline: Geriatric dogs showing signs of both Cushing's and canine cognitive dysfunction, where selegiline can address both conditions simultaneously.

What dose is used, how long until it works, and how long is it given?

Dosing selegiline requires careful titration and patience, as central neurotransmitter changes take time to manifest.

Dosing Protocol

Canine Cognitive Dysfunction (CDS): The recommended starting dose is 0.5 mg/kg orally once daily, administered in the morning.
Pituitary-Dependent Cushing's Disease: The starting dose is 1.0 mg/kg orally once daily, administered in the morning.

Morning administration is recommended because the metabolized L-amphetamine and L-methamphetamine compounds can cause mild stimulation. Giving the medication in the morning helps align this stimulatory effect with the dog's normal daytime activity and prevents nighttime restlessness.

Titration and Evaluation Timeline

Owners must be counseled that selegiline does not work overnight.

CDS Timeline: Allow a minimum of 4 to 6 weeks of daily administration to evaluate the drug's efficacy. A clinical response is defined as an improvement in DISHAA signs (e.g., less pacing, improved sleep patterns, fewer house-soiling accidents). If no improvement is noted after 4 weeks, and no side effects are present, the dose can be increased to a maximum of 1.0 to 2.0 mg/kg once daily. If no response is observed after 8 weeks at the maximum dose, therapy should be discontinued as a non-responder.
Cushing's Timeline: Clinical signs (reductions in drinking, urinating, and panting) should be monitored over 8 weeks. Unlike trilostane, selegiline does not require frequent ACTH stimulation tests for monitoring, as it does not carry a risk of causing adrenal necrosis. Instead, monitoring is based on clinical signs and liver enzyme monitoring. If response is inadequate after 8 weeks, the dose can be increased to 2.0 mg/kg once daily.

If selegiline is effective, it is continued lifelong. Stopping the medication will result in a rapid return of neurotransmitter depletion and a recurrence of clinical signs.

What side effects should owners watch for, and can they mimic dementia?

While selegiline is generally well tolerated, side effects can occur—particularly in geriatric patients with pre-existing conditions.

openFDA Adverse Event Data Analysis

To understand the real-world safety profile of selegiline, we analyzed the US FDA Center for Veterinary Medicine adverse-event database (run 20260705_full). Selegiline appeared in 4,504 unique reports, representing a highly dog-heavy dataset:

Canine Reports: 4,117 (91.4%)
Feline Reports: 39 (0.9%)
Other/Unknown: 348 (7.7%)

The most frequently reported adverse reactions include:

VeDDRA Reaction Term	Report Count	Clinical Context & Pathophysiology
Vomiting	456	Primary gastrointestinal irritation. Often managed by giving the medication with a small amount of non-protein food (such as a piece of bread or potato, avoiding tyramine-rich foods).
INEFFECTIVE, COGNITIVE DYSFUNC	441	Reflects the variable response and progressive nature of CDS. It is critical to prepare owners for the reality of partial response.
Diarrhoea	340	Secondary GI irritation; typically self-limiting.
INEFFECTIVE, LOSS OF EFFECT	338	Reflects the progression of underlying neurodegeneration over time. As brain tissue continues to atrophy, enhancing dopamine eventually becomes insufficient.
Anorexia	327	Appetite suppression, a known effect of central dopaminergic stimulation and amphetamine metabolites.
Depression	306	Lethargy or dullness, which can occur as a transient side effect or reflect the progression of the underlying disease.
Restlessness	263	Hyperactivity, agitation, or pacing. This is directly related to the stimulatory effects of dopamine and amphetamine metabolites.
INEFFECTIVE, CUSHINGS	252	Reflects the low success rate of selegiline for pituitary-dependent Cushing's compared to adrenal-blocking drugs.
Death by Euthanasia	243	Geriatric population context. These reports typically represent end-stage decisions for dogs with advanced dementia or Cushing's.
Convulsion (Seizures)	233	Selegiline should be used with caution in dogs with a history of epilepsy, as central stimulation can theoretically lower the seizure threshold.

The Diagnostic Challenge: Side Effects vs. Dementia Progression

A critical clinical point is that several common side effects of selegiline can mimic the very symptoms of dementia being treated. Specifically, restlessness, agitation, disorientation, and altered sleep patterns can be caused by the stimulatory effects of selegiline's metabolites.

If a dog becomes more agitated or paces more after starting selegiline, the veterinary team must determine whether this represents:

Drug Toxicity/CNS Stimulation: The dose is too high or the dog is unusually sensitive. The agitation typically starts shortly after initiating therapy or escalating the dose.
Disease Progression: The dementia is worsening.

To differentiate, a temporary dose reduction can be performed. If the restlessness resolves with a lower dose, it was likely drug-induced.

What drugs and foods must selegiline not be combined with (the MAOI interaction)?

The most critical safety aspect of using selegiline in dogs is its potential for severe, life-threatening drug interactions. As a monoamine oxidase inhibitor, selegiline blocks the primary pathway for neurotransmitter degradation, leaving the body highly vulnerable to excesses of serotonin and norepinephrine.

1. Serotonin Syndrome: The Primary Risk

Serotonin syndrome is a toxic state caused by an excess of serotonin in the central nervous system. It occurs when selegiline is combined with other drugs that increase serotonin levels, such as:

Selective Serotonin Reuptake Inhibitors (SSRIs): Fluoxetine (Reconcile, Prozac) or sertraline.
Tricyclic Antidepressants (TCAs): Clomipramine (Clomicalm) or amitriptyline.
Other MAOIs: Amitraz (present in some flea/tick collars and dips).
Serotonergic Analgesics: Tramadol (which inhibits serotonin reuptake) or fentanyl.
Dextromethorphan: Common in over-the-counter cough medications.

The symptoms of serotonin syndrome in dogs include:

Autonomic Effects: Salivation, vomiting, diarrhea, rapid heart rate (tachycardia), rapid breathing (polypnea), dilated pupils, and elevated body temperature (hyperthermia).
Neuromuscular Effects: Muscle tremors, rigidity, hyperreflexia, and ataxia.
Mental Status: Agitation, vocalization, disorientation, and seizures.

2. The Washout Rule (Prescribing Decision Map)

To prevent serotonin syndrome, veterinary teams must enforce strict washout periods when switching a dog between selegiline and any serotonergic medication:

               [THE Behavioral DRUG WASHOUT PROTOCOL]

  Switching FROM Fluoxetine (Reconcile)  --->  Wait 5 - 6 WEEKS
  TO Selegiline (Anipryl)                       (Fluoxetine's long half-life)
  
  Switching FROM Clomipramine            --->  Wait 14 DAYS
  (Clomicalm) TO Selegiline                     (Allows enzymes to clear)

  Switching FROM Selegiline              --->  Wait 14 DAYS
  TO any SSRI, TCA, or Tramadol                 (Allows brain to regenerate MAO)

Switching FROM another drug TO selegiline:
- If the dog was on fluoxetine (Reconcile), you must wait 5 to 6 weeks before starting selegiline, due to the extremely long half-life of fluoxetine and its active metabolite (norfluoxetine).
- If the dog was on clomipramine (Clomicalm) or amitriptyline, you must wait 14 days before starting selegiline.
- If the dog was on tramadol, you must wait 7 to 10 days before starting selegiline.
Switching FROM selegiline TO another drug:
- Because selegiline is an irreversible inhibitor, the body must synthesize new MAO-B enzymes to restore normal function. This process takes time. You must wait at least 14 days after stopping selegiline before starting any SSRI, TCA, or tramadol.

For comparison to adjacent behavior therapies, see our guide to Tessie (tasipimidine) for noise aversion and separation anxiety, which acts via a completely different pathway (alpha-2 adrenoceptor agonist) and does not share the MAOI interaction profile.

3. The "Cheese Effect" (Tyramine Interaction)

In humans taking non-selective MAOIs, consuming foods high in tyramine (such as aged cheeses, red wine, and cured meats) can cause a life-threatening hypertensive crisis known as the "cheese effect." Tyramine is a sympathomimetic amine that is normally broken down by MAO-A in the gut. If MAO-A is inhibited, tyramine enters the bloodstream and displaces norepinephrine, causing severe vasoconstriction and hypertension.

Fortunately, because selegiline is selective for MAO-B at recommended veterinary doses, the risk of a tyramine-induced hypertensive crisis in dogs is extremely low. However, as a precaution, dogs taking selegiline should not be fed aged cheeses, cured meats, or yeast extracts, and the dose should never exceed 2.0 mg/kg/day to preserve MAO-B selectivity.

Clinical Monitoring and Success Criteria for Selegiline Therapy

Initiating selegiline therapy is a long-term commitment that requires structured clinical monitoring to maximize safety and document efficacy. Because the drug is primarily prescribed to geriatric canine patients, distinguishing therapeutic success from underlying disease progression or concurrent comorbidities is a core task for the veterinary team.

1. Baseline and Routine Laboratory Screening

Before starting selegiline, a complete baseline laboratory assessment is indicated. This is not because selegiline is inherently toxic, but because its metabolism and excretion depend on organ function:

Liver Function: Selegiline undergoes extensive hepatic metabolism via cytochrome P450 enzymes to produce its L-amphetamine and L-methamphetamine metabolites. Dogs with severe hepatic impairment may experience delayed clearance and heightened sensitivity to the stimulatory side effects.
Kidney Function: The metabolized compounds are excreted primarily through the kidneys. Geriatric dogs with chronic kidney disease (CKD) should have their dosing carefully evaluated, and renal values (BUN, creatinine, SDMA) monitored to ensure clearance.
Monitoring Schedule: A complete chemistry panel, hematology, and urinalysis should be performed before starting the drug, repeated at 2 to 4 weeks after initiation, and then evaluated every 6 months as part of routine senior wellness monitoring.

2. Documenting Efficacy in Cognitive Dysfunction (CDS)

Relying on vague owner descriptions like "he seems a bit better" makes it difficult to judge whether to continue therapy. Instead, veterinarians should use structured scoring scales completed by the owner:

CADES (Canine Cognitive Dysfunction Rating Scale): This validated scale evaluates 17 behavioral items across four domains: Spatial Orientation, Social Interactions, Sleep-Wake Cycles, and House-soiling. It categorizes impairment as Mild (score 8–23), Moderate (score 24–44), or Severe (score 45–95).
Evaluation Interval: The CADES questionnaire should be filled out by the owner at baseline, at 4 weeks (to determine if a dose increase is needed), at 8 weeks, and then every 3 months. A successful response is defined as a stabilization or decrease in the overall score, or a delay in the progression from mild to moderate impairment.
Managing "Lack of Response": If the dog's CADES score continues to rise rapidly despite reaching the maximum dose of 2.0 mg/kg/day, it indicates that the neurodegenerative process has bypassed the capacity of dopaminergic enhancement. At this point, the medication should be discontinued, and the clinical focus should shift to palliative care, environmental enrichment, or other nutritional interventions.

3. Monitoring Pituitary-Dependent Cushing's (PDH)

For dogs taking selegiline to control Cushing's disease, the monitoring parameters are distinct from standard adrenal-blocking therapies:

Water Intake Log: The most direct indicator of response is a reduction in polydipsia (excessive drinking). Owners should measure daily water intake. A successful response is indicated when water consumption drops below the polydipsia threshold of 100 mL/kg/day, ideally reaching a normal maintenance range of 50 to 60 mL/kg/day.
Urine Specific Gravity (USG): Cushing's dogs typically have dilute urine (USG < 1.008–1.010). As ACTH secretion is brought under dopaminergic control, the kidneys regain their concentrating ability, resulting in a rising USG (ideally > 1.015–1.020).
Systemic Blood Pressure: Hyperadrenocorticism causes systemic hypertension. Blood pressure should be measured at each recheck, with a target systolic pressure of < 140 to 150 mmHg to minimize target-organ damage. If hypertension persists despite selegiline therapy, secondary anti-hypertensive medications (such as amlodipine) are indicated.

Selegiline for Dogs FAQs

How long does it take for selegiline (Anipryl) to work for dog dementia, and how do I know if it is helping?

Allow a minimum of 4 to 6 weeks of daily morning administration to evaluate selegiline. You will know it is helping if you observe a reduction in DISHAA signs—such as less aimless wandering during the day, fewer nighttime waking cycles, or decreased pacing and vocalization. Some dogs show partial improvement, while others may require a dose escalation up to 2.0 mg/kg once daily.

Can selegiline be given with fluoxetine (Reconcile) or clomipramine (Clomicalm)?

No. Combining selegiline with SSRIs like fluoxetine or TCAs like clomipramine can cause serotonin syndrome, a life-threatening crisis of neuromuscular rigidity, muscle tremors, hyperthermia, tachycardia, and seizures. A strict washout window of 14 days (or 5 to 6 weeks if switching from fluoxetine) is required.

Is selegiline a cure for canine cognitive dysfunction or Cushing's?

No. Selegiline is a palliative therapy. For canine cognitive dysfunction, it Enhances dopamine levels to manage cognitive decline but does not halt brain atrophy or amyloid deposition. For Cushing's, it attempts to restore dopaminergic control over pituitary ACTH secretion, but it does not treat adrenal tumors or resolve pituitary microadenomas.

What are the most common side effects of Anipryl in older dogs?

Based on openFDA data, the most common side effects are gastrointestinal (vomiting, diarrhea, and decreased appetite/anorexia) and behavioral (restlessness, agitation, or hypersensitivity to stimulation). Agitation and pacing can sometimes mimic the progression of dementia, requiring a diagnostic dose reduction.

Sources

U.S. Food and Drug Administration (FDA). Anipryl (selegiline hydrochloride) tablets prescribing information (NADA 141-080). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=84e25a59-1db6-42bf-b27e-a25c4883a141
Zoetis US. Anipryl Prescribing Information. https://www.zoetisus.com/content/_assets/docs/vmips/package-inserts/anipryl-prescribing-information.pdf
Merck Veterinary Manual. Canine Cognitive Dysfunction. https://www.merckvetmanual.com/nervous-system/congenital-and-inherited-anomalies-of-the-nervous-system/canine-cognitive-dysfunction
VCA Animal Hospitals. Selegiline (Anipryl). https://vcahospitals.com/know-your-pet/selegiline
U.S. Food and Drug Administration (FDA). openFDA Animal and Veterinary Adverse Event Database (run 20260705_full; active ingredient selegiline; unique_aer_id_number filters).

Vet Med Guide

Selegiline (Anipryl) for Dogs: Cognitive Dysfunction, Cushing's, and the MAOI Reality