Abstract

Paroxetine (Paxil®, SmithKline Beecham Pharmaceuticals, Philadelphia, PA, USA) is a selective serotonin reuptake inhibitor (SSRI) used to treat human patients diagnosed with psychiatric conditions such as depression, anxiety, obsessive-compulsive disorder, and post-traumatic stress disorder.¹ Its advantages over tricyclic antidepressants include an absence of cardiovascular side effects, and a wide margin of safety. Of the SSRIs used for disorders involving self-mutilation, paroxetine appears to be one of the few with a fairly low incidence of side effects. In human patients, the main side effect commonly seen with paroxetine is lethargy (Gregory McFadden, MD, PhD, personal communication, 2002).

While the causes of feather picking or self-mutilation in avian patients may at times be difficult to determine, it is widely held that a large number of these cases have a strong behavioral component and/or may become exacerbated by stress. It could be postulated that some of these veterinary cases may be analogous to severe anxiety or obsessive-compulsive disorders in humans.

At the San Diego Zoo, two Waldrapp ibis (Geronticus eremita) presented with histories of chronic feather picking and self-mutilation of the dorsal thorax. The wounds were debrided and bandages changed for several weeks. Paroxetine therapy was initiated gradually, starting at 0.3 mg/kg once daily (SID) PO for the first week, followed by 0.6 mg/kg SID PO for the next 2 weeks, and finally 1.0 mg/kg SID PO. The birds began to show a decreased frequency of picking and mutilation 4 days after therapy was initiated. One month later, these behaviors appeared to have stopped. After 15 months of therapy, the dosage was increased to 2.0 mg/kg SID PO whenever it appeared that the birds were picking again. The dosage was increased gradually in this situation due to a lack of published information on appropriate dosages for avian species. Since treatment of these ibises was initiated, the use of paroxetine in laboratory pigeons (Columba livia) has been reported. The dosage used in the pigeon was 3 mg/kg SID PO.² Long-term oral paroxetine, administered once daily in a mouse, allowed the wounds to heal to the point of small scabs. During this time, the wounds required debridement and bandage changes for several months. Complete blood counts and serum chemistries were performed monthly for the first 6 months, and then q 90 days for the following 12 months. Results of these tests suggested no evidence of adverse effects from the medication. Lethargy was not observed in these birds. Periodic serum paroxetine levels were performed. Although the actual numeric quantity of paroxetine in the blood does not correlate with degree of clinical effect in human patients, this testing did at least allow us to verify that the drug was being absorbed from the gastrointestinal tract in our ibises. At the San Diego Zoo, treatment with paroxetine has also been used successfully in some individuals of other species: a feather-picking hyacinth macaw (Anodorhynchus hyacinthinus) and a self-mutilating Allen’s swamp guenon (Allenopithecus nigroviridis).

Although no side effects were observed while any of these animals were on paroxetine, care should be taken to taper the dosage over at least 3 weeks if treatment is to be discontinued. Stopping paroxetine treatment abruptly in human patients may cause withdrawal symptoms such as nausea, hypomania, and dizziness.¹

Acknowledgments

I would like to thank the San Diego Zoo veterinarians, registered veterinary technicians, and hospital keepers for their long-term, dedicated care of these birds.

Literature Cited

1.  Green, B. 2003. Focus on paroxetine. Curr. Med. Res. Opin. 19:13–21.

2.  Wolff, M.C., and J.D. Leander. 2002. Selective serotonin reuptake inhibitors decrease impulsive behavior as measured by an adjusting delay procedure in the pigeon. Neuropsychopharmacology. 27(3):421–429.