Paroxetine

What it is used for

• SSRI responsive behavior problems
• Compulsive disorders
• Generalized anxiety disorder
• Marking
• Intercat aggression
• SSRI responsive behavior problems
• Urine marking (especially with overt aggression)
• Compulsive disorders
• Generalized anxiety disorder
• Adjunctive treatment of phobias, fears, and anxieties
• Generalized anxiety and impulsivity

How it is given

Possible side effects

• Anorexia (common, usually transient)
• Lethargy
• GI effects
• Anxiety
• Irritability
• Insomnia/hyperactivity
• Panting
• Aggressive behavior in previously unaggressive dogs
• Constipation (especially in cats)
• Changes in elimination patterns
• Changes in blood glucose levels
• Reduced seizure threshold
• Decreased appetite
• Vomiting
• Trembling
• Restlessness
• Gastrointestinal disturbance
• Paradoxical increase in anxiety
• Potential increase in aggression
• Changes in urination frequency (cats)

Cautions & contraindications

• Patients with known hypersensitivity to paroxetine
• Patients receiving monoamine oxidase inhibitors (MAOIs)
• Known hypersensitivity to paroxetine or other SSRIs
• History of seizures or epilepsy
• Concurrent use of Monoamine Oxidase Inhibitors (MAOIs)
• Concurrent use of other serotonergic agents (due to serotonin syndrome risk)
• Use with caution in patients with **seizure disorders**, or **severe cardiac, hepatic, or renal disease**. Dosages may need to be reduced in patients with severe hepatic or renal impairment. If paroxetine is rapidly discontinued, withdrawal reactions can occur. If the patient has been receiving the drug for an extended period, a **gradual withdrawal** is recommended. Safety during pregnancy has not been established (FDA Category C in humans); use caution in nursing patients as the drug is excreted into milk at low levels.

Drug interactions

• Buspirone: Increased risk for serotonin syndrome
• Cimetidine: May increase paroxetine levels
• Cyproheptadine: May decrease or reverse the effects of SSRIs
• Digoxin: Paroxetine (in humans) can decrease digoxin AUC by 15%
• Insulin: May alter insulin requirements
• Isoniazid: Increased risk for serotonin syndrome
• MAO Inhibitors (including amitraz and selegiline): High risk for serotonin syndrome; use contraindicated. A 5-week washout period is required after discontinuing paroxetine, and a 2-week washout if discontinuing the MAOI first.
• Pentazocine: Serotonin syndrome-like adverse effects possible
• Phenobarbital: May decrease paroxetine levels
• Phenytoin: Increased plasma levels of phenytoin possible; may decrease paroxetine levels
• Propranolol, Metoprolol: Paroxetine may increase these beta-blockers' plasma levels and cause hypotension; atenolol may be safer
• Tramadol: SSRIs can inhibit the metabolism of tramadol to active metabolites, decreasing efficacy and increasing toxicity risk (serotonin syndrome, seizures)
• Tricyclic Antidepressants (e.g., clomipramine, amitriptyline): Paroxetine may increase TCA blood levels and may increase the risk for serotonin syndrome
• Theophylline: Increased plasma levels of theophylline possible
• Warfarin: Paroxetine may increase the risk for bleeding
• Selegiline (and other MAOIs): High risk of fatal serotonin syndrome. Do not use paroxetine within 2 weeks of an MAOI, and do not use an MAOI within 6 weeks of stopping paroxetine.
• Anticonvulsants: Paroxetine antagonizes the effects of anticonvulsants and lowers the seizure threshold.
• Phenothiazines: May lower seizure threshold and increase risk of adverse neurological events.
• Aspirin: Increased risk of bleeding in the case of tissue trauma.
• Anticoagulants: Increased risk of bleeding.
• Trazodone: Increased risk of serotonin syndrome. Use only in exceptional cases with careful monitoring.

Frequently asked questions