Selegiline
Selegiline (L-deprenyl) is a monoamine oxidase inhibitor authorized for the treatment of behavioural disorders of purely emotional origin, such as **depression** and **anxiety**. It is often used in association with behaviour therapy for conditions involving overactivity, separation problems, generalized phobia, and unsociable behaviour. These emotional disorders are typically characterized by modifications in feeding, drinking, autostimulatory behaviour, sleep, exploratory behaviour, fear/irritation-related aggression, and somatic disorders (e.g., tachycardia, emotional micturition). > **Clinical Pearl:** Selegiline is highly indicated for **canine cognitive dysfunction (CCD)**, especially when associated with anxiety or social withdrawal, and can also be used to treat signs of cognitive decline in older cats. Uniquely, treatment can be stopped suddenly without the need for gradual dose reduction.
Mechanism: Selegiline modifies the concentration of monoaminergic neurotransmitters, especially **phenylethylamine** and **dopamine**, by selectively inhibiting the activity of **Type-B monoamine oxidase (MAO-B)**, the enzyme that normally breaks down these chemicals. MAO-B inhibition → decreased breakdown of dopamine → increased dopamine concentrations in the CNS. It also appears to possess **neuroprotective properties**.
Dosing by species
- Behavioural disorders and cognitive dysfunction · 0.5-1 mg/kg · PO · q24h · minimum of 2 months · Treatment can be stopped suddenly without gradual dose reduction.
- Cognitive decline in older cats · 1 mg/kg · PO · q24h · Not specified · Treatment can be stopped suddenly without gradual dose reduction.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Known sensitivity to selegiline
- Lactating bitches (acts on prolactin secretion)
- Pregnant bitches
Adverse effects
- No specific adverse reactions are listed in the monograph
- Clinical Pearl: May occasionally cause mild gastrointestinal upset, restlessness, or lethargy
Drug interactions
- Alpha-2 antagonists · Should not be administered concurrently or within 24 hours before/after use · major
- Pethidine · Contraindicated concurrent use · major
- Ephedrine · Contraindicated concurrent use · major
- Amitraz · Potential MAOI interaction; contraindicated · major
- Phenothiazines · Contraindicated concurrent use · major
- Morphine · Potentiates the effect of morphine · moderate
- Metronidazole · Potential interaction exists · minor
- Prednisolone · Potential interaction exists · minor
- Trimethoprim · Potential interaction exists · minor
- Tricyclic antidepressants (amitriptyline, doxepin, clomipramine) · Do not use selegiline for at least 2-3 weeks after TCA use · major
- Fluoxetine · Do not use selegiline for at least 6 weeks after long-term fluoxetine use · major
Monitoring
- Improvement in behavioural signs (anxiety, phobias, social withdrawal)
- Improvement in cognitive function (disorientation, sleep-wake cycle alterations)
- Adverse drug interactions if other medications are introduced
Overdose
No specific overdose information is provided in the monograph. **Clinical Pearl:** Overdoses of MAOIs can lead to signs of serotonin syndrome or excessive dopaminergic stimulation, including hyperthermia, tachycardia, tremors, and agitation. Treatment is supportive.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.