AJVR, Vol 63, No. 6, June 2002 827 D rug interactions may result in serious physiologic consequences, and drugs classified as monoamine oxygenase (MAO) inhibitors have been implicated as participants in several adverse drug interactions. 1-3 Selegiline (L-deprenyl) is a MAO inhibitor approved for use in treatment of dogs with pituitary-dependent hyperadrenocorticism 4 and cognitive dysfunction, 5 dis- orders that are common in older dogs. Similar to other MAO inhibitors, selegiline leads to accumulation of sympathetically active endogenous substances by inhibiting the breakdown of endogenous cate- cholamines. 6 In addition, selegiline is metabolized to L-amphetamine, a potent sympathomimetic and CNS stimulant. 6 Geriatric dogs with hyperadrenocortisolism or cognitive dysfunction are often examined by veterinar- ians because of urinary incontinence or house soil- ing. 7,8 Urinary incontinence in dogs has often been treated with phenylpropanolamine (PPA). 9 Despite its recent removal from the human pharmaceutical mar- ket, PPA remains available to veterinarians and is like- ly to still be widely used in the treatment of dogs with idiopathic urinary incontinence. a-c Similar to selegiline, PPA is a sympathomimetic drug. Treatment of geriatric dogs is a growing compo- nent of veterinary practice. Similar to geriatric people, geriatric dogs are likely to concurrently receive > 1 type of medication. In particular, it is to be expected that there will be situations when older dogs may be treated concurrently with selegiline and PPA. Because both drugs may result in catecholamine accumulation, the combination of the 2 drugs has the potential to result in adverse clinical effects, particularly effects related to the cardiovascular system. 10 Currently, the company that markets selegiline for use in animals cautions against its simultaneous use with ephedrine, a drug similar to PPA. 11,d The purpose of the study report- ed here was to investigate the effects of selegiline, PPA, and the combination of these 2 drugs on certain rele- vant physiologic variables in dogs as well as to monitor pronounced changes in behavior of treated dogs. Materials and Methods Animals—Forty mixed-breed hound-type dogs were enrolled in the study. Although true ages were unknown, all dogs were adults, and most were estimated to be between 3 and 5 years of age. Dogs weighed between 21.2 and 33.3 kg. Before admission to the study, each dog was evaluated on the basis of results of physical examination, occult heartworm serologic analysis, CBC, serum biochemical analysis, and parasitologic examination of a fecal sample. Three dogs had substantial hyperglobulinemia and were subsequently seropositive for Ehrlichia canis. These dogs received a 10-day course of doxycy- cline that was completed 1 week prior to initiation of the study. All other dogs were judged to be in good overall health. Dogs were randomly allocated into 4 groups, each of which con- tained an equal number of sexually intact males and females. Dogs were housed in a routine manner in animal facili- ties accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International. All experimental procedures were reviewed and approved by the University of Missouri Animal Care and Use Committee. Study protocol—Before initiation of the study, each dog was acclimated to handling, restraint in right lateral recum- Received Nov 15, 2001. Accepted Jan 11, 2002. From the Departments of Veterinary Medicine and Surgery (Cohn, Dodam, Szladovits) and Veterinary Biomedical Sciences (Dodam), College of Veterinary Medicine, University of Missouri, Columbia, MO 65211. Supported by Pfizer Animal Health. The authors thank Dr. Richard Madsen for statistical assistance. Address correspondence to Dr. Cohn. Effects of selegiline, phenylpropanolamine, or a combination of both on physiologic and behavioral variables in healthy dogs Leah A. Cohn, DVM, PhD; John R. Dodam, DVM, PhD; Balazs Szladovits, DVM Objective—To determine effects of selegiline hydrochloride, phenylpropanolamine (PPA), or a com- bination of both on physiologic and behavioral vari- ables in dogs. Animals—40 adult hound-type dogs. Procedure—Dogs were assigned to 4 groups. One group received selegiline (1 mg/kg, PO, q 24 h) and PPA (1.1 mg/kg, PO, q 8 h), a second group received selegiline alone, a third group received PPA alone, and a fourth group received neither drug. Dogs were observed 3 times/d throughout the 30-day study (daily during the first week, on alternate days during the next 2 weeks, and again daily during the final week). Observers recorded rectal temperature, pulse, respi- ratory rate, oscillometric blood pressure, and lead-II ECG and assessed 4 behaviors, using an analogue scale. Variables were compared among treatment groups by use of a 2-factor ANOVA with data catego- rized into three 10-day treatment periods. A similar comparison was made among treatment groups with data categorized by time of observation (morning, afternoon, or evening) for all study days. Results—Variables did not differ among groups at study initiation. Pulse rate was the only variable that differed significantly among treatment groups during the study. During the first 10 days of treatment, dogs receiving PPA had a lower pulse rate than dogs that did not. Although signs of illness were apparent in a few dogs, illness did not appear to be related to treat- ment. Conclusions and Clinical Relevance—Adverse effects were not detected after administration of selegiline, PPA, or a combination of the drugs in healthy dogs. (Am J Vet Res 2002;63:827–832) Unauthenticated | Downloaded 08/13/22 01:59 PM UTC