234 DISEASES/DISORDERS
Behavior-modifying medication:
Analgesic/anticonvulsant:
Gabapentin – dog: 10–20 mg/kg q12h: cat: 5–10 mg/kg q12h
Selective serotonin reuptake inhibitors:
Fluoxetine – dog: 1.0–2.0 mg/kg q24h; cat: 0.5–1.0 mg/kg q24h
Paroxetine– dog: 0.5–1.0 mg/kg q24h; cat: 1.0–2.5 mg q24h
Sertraline: dog: 0.5–2.5 mg/kg q24h; cat: 0.5–1.0 mg/kg q24h
Tricyclic antidepressants:
Amitriptyline: dog: 1.0–2.2 mg/kg q12–24h; cat: 0.5–1.0 mg/kg q12–24h
Clomipramine: dog: 1.0–2.0 mg/kg q12–24h; cat: 0.5–1.0 mg/kg q24h
Doxepin: Initial dosage 1mg/kg q12h with gradual increase up to 3.0–
5.0 mg/kg q8–12h (maximum 150 mg BID); cat: 0.5 mg/kg q24h.
COMMENTS
Begin with a low dose of behavior-modifying medication and increase biweekly if
there is inadequate response.
Serotonin-enhancing medications: long-acting anxiolytics.
Doxepin and amitriptyline are also H 1 blockers; may be useful in cases with allergy.
Treatment goal is to interrupt the conditioned response while resolving the organic
disease and/or modifying the behavior.
Reports of success with other psychoactive medications are limited (e.g.,
hydrocodone, naltrexone).
Few of these medications are FDA-approved for use in animals.
Some medications may lower the seizure threshold; gabapentin is beneficial in seizure
patients.
Do not use with MAO inhibitors (e.g., amitraz, selegiline).
Obtain a minimum database to ascertain the patient’s ability to metabolize and excrete
medications (especially hepatic disease).
Monitor patients regularly during therapy.
Avoid concomitant use of multiple serotonin-enhancing medications to prevent side
effects including fatal serotonin syndrome.
Use cautiously with other highly protein-bound medications (anticonvulsants, thy-
roid medications, nonsteroidal antiinflammatory drugs) as well as with general anes-
thesia, anticholinergics, antihistamines, and anticoagulants.Avoid use of tricyclic antidepressants in patients with cardiac conduction abnormal-
ities or with glaucoma.
Avoid sudden changes in dosages; gradual increases and decreases are recommended.
Common side effects include reduced appetite and sedation, dry mouth, urine reten-
tion, constipation, reduced tear production, and increased agitation.
Medications may take 4–8 weeks to achieve efficacy.
Symptoms of overdose include behavioral changes (agitation, depression), tremors,
ataxia, seizures, hyperthermia, and diarrhea; fatal serotonin syndrome reported.
Treatment of toxicosis is supportive and symptomatic; cyproheptadine hydrochloride
(1.1 mg/kg PO) is a nonspecific serotonin antagonist.