Sertraline
Sertraline is a widely used human antidepressant that is utilized off-label in veterinary medicine to manage a variety of behavior-related diagnoses in dogs and cats. **Key Clinical Applications:** * **Dogs:** Aggression, generalized anxiety, and obsessive-compulsive behaviors (e.g., acral lick dermatitis, tail chasing). * **Cats:** Urine marking (spraying), affective or dominance aggression, anxiogenic house soiling, phobias, and compulsive disorders. **Clinical Pearls:** > Like other SSRIs, sertraline requires a prolonged duration of therapy (typically 4 to 8 weeks) before full clinical efficacy is observed. This delay is due to the time required for neuroreceptor down-regulation. It is relatively inexpensive due to the availability of generic formulations, making it an attractive option for long-term behavioral management.
Mechanism: Sertraline is a highly selective inhibitor of the presynaptic reuptake of **serotonin (5-hydroxytryptamine or 5-HT)** in the central nervous system. * **Mechanism:** Blocks the **serotonin transporter (SERT)** โ prevents the reuptake of serotonin into the presynaptic neuron โ increases the concentration of serotonin in the synaptic cleft โ prolongs stimulation of postsynaptic **5-HT receptors**. * **Receptor Specificity:** Sertraline has minimal to no effect on the reuptake of dopamine or norepinephrine, and lacks significant affinity for adrenergic, cholinergic, or histaminergic receptors, which minimizes the side effects typically seen with tricyclic antidepressants (TCAs). * **Delayed Onset:** The initial increase in synaptic serotonin stimulates presynaptic **5-HT1A autoreceptors**, which temporarily decreases serotonin release. Over several weeks, these autoreceptors down-regulate, allowing for enhanced serotonin release and the onset of full therapeutic effects.
Dosing by species
- Treatment of compulsive disorders ยท 0.5 mg/kg PO once daily ยท PO ยท q24h
- Urine marking (spraying), aggression, anxiety-including anxiogenic house soiling, phobias, fears ยท 0.5-1 mg/kg PO q24h (once daily) ยท PO ยท q24h
- Treatment of behavioral diagnoses ยท 1 mg/kg PO q24h (once a day) ยท PO ยท q24h ยท Minimum 4-6 months ยท Treat for 3-5 weeks minimum to assess effects; treat until 'well' (minimum another 1-2 months), then treat another 1-2 months minimum. Wean off over 3-5 weeks or longer.
- Treatment of fear, affective or dominance aggression ยท 0.5-1 mg/kg PO once daily ยท PO ยท q24h
- Generalized anxiety disorder ยท 0.5-1.5 mg/kg PO q24h ยท PO ยท q24h
- Treatment of compulsive disorder, anxiety ยท 0.5-1 mg/kg PO q24h (once daily) ยท PO ยท q24h
- Behavioral diagnoses ยท 0.25-1.3 mg/kg PO q24h ยท PO ยท q24h
- Increase inhibitory control (e.g., play-related aggressive behaviour) ยท 0.5-1.5 mg/kg ยท PO ยท q24h ยท Long-term ยท Suggested use, but there are no good empirical studies published to support this.
- Treatment of compulsive disorders ยท 2-4 mg/kg PO once daily or divided twice daily ยท PO ยท q24h or q12h
- Behavioral diagnoses ยท 1-2 mg/kg PO q24h (once daily) ยท PO ยท q24h ยท allow 6-8 weeks for initial trial
Routes of administration
Contraindications
- Known hypersensitivity to sertraline or other SSRIs
- Concurrent use of Monoamine Oxidase Inhibitors (MAOIs) such as selegiline or amitraz
- Concurrent use of cisapride
- History of seizures or epilepsy
- Concurrent use of MAOIs (e.g., selegiline)
Adverse effects
- Anorexia (common in dogs, usually transient)
- Lethargy or sedation
- Gastrointestinal effects (vomiting, diarrhea)
- Anxiety or irritability
- Insomnia or hyperactivity
- Panting (dogs)
- Changes in elimination patterns (cats)
- Paradoxical aggressive behavior in previously non-aggressive animals
- Lethargy
- Decreased appetite
- Vomiting
- Trembling
- Restlessness
- Gastrointestinal disturbance
- Paradoxical increase in anxiety
- Potential increase in aggression
Drug interactions
- Buspirone ยท Increased risk for serotonin syndrome
- Cimetidine ยท May increase sertraline levels
- Cyproheptadine ยท May decrease or reverse the effects of SSRIs
- Diazepam ยท Sertraline may decrease diazepam clearance
- Isoniazid ยท Increased risk for serotonin syndrome
- MAO Inhibitors (e.g., amitraz, selegiline) ยท High risk for serotonin syndrome; use contraindicated. A 5-week washout period is required after discontinuing sertraline before starting an MAOI, and a 2-week washout if discontinuing an MAOI before starting sertraline.
- Pentazocine ยท Serotonin syndrome-like adverse effects possible
- Tramadol ยท SSRIs can inhibit the metabolism of tramadol to active metabolites, decreasing efficacy and increasing the risk of toxicity (serotonin syndrome, seizures)
- Tricyclic Antidepressants (e.g., clomipramine, amitriptyline) ยท Sertraline may increase TCA blood levels and increase the risk for serotonin syndrome
- Warfarin ยท Sertraline may increase the risk for bleeding
- Selegiline (MAOIs) ยท High risk of fatal serotonin syndrome. Do not use sertraline within 2 weeks of an MAOI, and do not use an MAOI within 6 weeks of stopping sertraline. ยท major
- Anticonvulsants ยท Sertraline antagonizes the effects of anticonvulsants and lowers the seizure threshold. ยท major
Monitoring
- Efficacy (resolution or improvement of behavioral signs)
- Adverse effects, particularly changes in appetite and body weight
- Baseline liver function tests (consider re-testing as needed)
- Baseline ECG (consider re-testing as needed)
- Behavioral response (efficacy and paradoxical aggression/anxiety)
- Appetite and body weight
- Signs of serotonin syndrome (tremors, hyperthermia, agitation)
- Seizure activity
Overdose
**Toxicity Profile:** Most exposures in dogs below 20 mg/kg are not considered serious. However, massive overdoses can be life-threatening. **Clinical Signs of Overdose:** * **Mild to Moderate:** Vomiting, diarrhea, hypersalivation (especially in cats), lethargy, tachycardia, somnolence, and vocalization. * **Severe (Serotonin Syndrome):** Muscle tremors, rigidity, agitation, hyperthermia, vocalization, hypertension or hypotension, tachycardia, seizures, coma, and potentially death. **Management:** Handle aggressively with supportive and symptomatic treatment. Contact an animal poison control center (e.g., ASPCA APCC) for specific guidance.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.