Clinical evaluation of a single daily dose of phenylpropanolamine in the treatment of urethral sphincter mechanism incompetence in the bitch

The objective of this retrospective study was to determine the efficacy of a single daily oral dose of phenylpropanolamine (PPA) in the treatment of urethral sphincter mechanism incompetence (USMI) in bitches. Nine bitches diagnosed with USMI were treated with a single daily dose [1.5 mg/kg body weight (BW)] of PPA for at least 1 month. Urethral pressure profiles (UPP) were performed in 7 dogs before treatment and repeated in 4 of them after treatment. Treatment with PPA resulted in long-term continence in 8/9 bitches. One dog did not respond to PPA and was treated surgically later. Recheck UPPs showed a significant increase in maximal urethral closure pressure in the 4 bitches after treatment with PPA compared to before treatment. In conclusion, long-term continence can be achieved in bitches affected with USMI after administration of a single daily dose of PPA (1.5 mg/kg BW).     

Results of cystometry and urethral pressure profilometry in dogs sedated with medetomidine or xylazine

OBJECTIVE: To compare effects of medetomidine and xylazine hydrochloride on results of cystometry and micturition reflexes in healthy dogs and results of urethral pressure profilometry (UPP) in sedated and conscious dogs. ANIMALS: 20 dogs. PROCEDURES: Urodynamic testing was performed 6 times in each dog (3 times after administration of xylazine [1 mg/kg of body weight, IV] and 3 times after administration of medetomidine (30 microg/kg, IM). Before each episode of sedation, UPP was performed. Heart and respiratory rates and indirect blood pressures were recorded prior to and 5, 10, 20, and 30 minutes after injection of sedative. Cystometry measurements included threshold volume, threshold pressure, and tonus limb. The UPP measurements included maximal urethral closure pressure (MUCP), functional profile length, and, in male dogs, plateau pressure. RESULTS: Mean MUCP was decreased markedly in xylazine- and medetomidine-sedated dogs. Xylazine and medetomidine also decreased plateau pressure in male dogs. The MUCP measurements were consistent among days for conscious and xylazine-sedated dogs but were inconsistent for medetomidine-sedated female dogs. The proportion of valid cystometry measurements was greater for xylazine (39 of 60) than for medetomidine (27 of 60). Cystometry was considered invalid when bladder pressure reached 30 cm H2O without initiation of a micturition reflex. CONCLUSIONS AND CLINICAL RELEVANCE: Medetomidine and xylazine have similar effects on measurement of UPP and cystometry. Medetomidine was less consistent among days for UPP in female dogs and produced fewer valid cystometry tests, compared with xylazine. For urodynamic evaluations, medetomidine administered IM cannot be substituted for xylazine administered IV.     

Changes in blood pressure following escalating doses of phenylpropanolamine and a suggested protocol for monitoring

This prospective, cross-over, blinded study evaluated the effect of various doses of phenylpropanolamine (PPA) on blood pressure in dogs. Dogs were randomized to receive a placebo or 1 of 3 dosages of immediate release PPA, q12h for 7 days [1 mg/kg body weight (BW), 2 mg/kg BW, or 4 mg/kg BW] in a cross-over design. Blood pressure was recorded every 2 h, for 12 h, on days 1 and 7. There were significant increases in systolic, diastolic, and mean blood pressure following administration of PPA at 2 mg/kg BW and 4 mg/kg BW. A significant decrease in heart rate was also noted at all PPA dosages, but not in the placebo. Administration of PPA was associated with a dose response increase in blood pressure. Dosages of up to 2 mg/kg BW should be considered safe in healthy dogs.     

Effects of selegiline,phenylpropanolamine, or a combination of both on physiologic and behavioral variables in healthy dogs

OBJECTIVE: To determine effects of selegiline hydrochloride, phenylpropanolamine (PPA), or a combination of both on physiologic and behavioral variables 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, respiratory 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 categorized 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 treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Adverse effects were not detected after administration of selegiline, PPA, or a combination of the drugs in healthy dogs.     

Effects of urinary bladder distension on the length of the dog and cat urethra

Urethral lengths were determined in male and female cats and in female dogs from positive contrast retrograde urethrocystograms at 2 levels of urinary bladder distension. Urethral lengths were longer on urethrograms obtained after urinary bladder distension in female cats and in 7 of 8 female dogs. The intrapelvic and penile urethra were longer after bladder distension in 4 of 6 male cats. In female cats, urethral lengths significantly increased (P less than 0.05) after urinary bladder distension.     

Cardiovascular effects of butorphanol in halothane-anesthetized dogs

Cardiovascular effects of butorphanol (0.2 mg/kg of body weight, IV) and responses associated with subsequent administration of naloxone (0.04 mg/kg, IV) were studied in halothane (1.2% end-tidal concentration)-anesthetized dogs. Transient, but statistically significant (P less than 0.05), decreases in heart rate, mean and diastolic arterial blood pressures, and rate-pressure product were observed after butorphanol administration. Cardiac index, stroke volume, and systemic vascular resistance did not change significantly. Except for the decrease in heart rate, changes in the values of the cardiovascular variables measured after butorphanol administration did not appear to be clinically relevant. Sixty minutes after butorphanol administration, naloxone was given. Statistically significant (P less than 0.05) increases in heart rate, arterial blood pressures, cardiac index, and rate-pressure product, along with dysrhythmias were observed. Stroke volume and systemic vascular resistance remained unchanged after administration of naloxone. Naloxone administration was associated with changes indicative of increased myocardial oxygen consumption.     

The effects of the loop diuretics furosemide and torasemide on diuresis in dogs and cats

Torasemide is a new loop diuretic that combines the effects of furosemide and spironolactone. There are no reports on the effects of torasemide in cats and dogs. This study compared the diuretic effects of furosemide and torasemide in cats and dogs. Cats with pressure overload cardiac hypertrophy were given oral placebo, torasemide 0.3 mg/kg, or furosemide 1 mg/kg or 3 mg/kg. Control and mitral regurgitation dogs were given oral placebo, torasemide 0.2 mg/kg, and furosemide 2 mg/kg for 7 days. Urine samples were obtained at baseline and 1, 2, 3, 4, 5, 6, 8, 12, and 24 hr after each drug dose. Urine volume and urine Na(+) and K(+) were measured. Both furosemide and torasemide increased urine volume 1 hr after administration. Furosemide caused a dose-dependent increase in urine volume that peaked at 2-3 hr in cats and dogs. The diuretic effect of furosemide disappeared 6 hr after administration, while that of torasemide peaked 2-4 hr after administration and persisted for 12 hr in cats and dogs. In MR dogs, torasemide for 7 days significantly decreased urine potassium excretion. Plasma aldosterone increased with torasemide, whereas there was no change with furosemide. In conclusion, about 1/10 concentration of torasemide was as potent as furosemide and had a longer diuretic effect in cats and dogs. These data suggest that torasemide is useful for treating congestive heart failure or edema in cats and dogs.     

Serum concentrations of thyroxine and 3,5,3'-triiodothyronine in dogs before and after administration of freshly reconstituted or previously frozen thyrotropin-releasing hormone

Concentrations of serum thyroxine (T4) and 3,5,3'-triiodothyronine (T3) were determined after the administration of freshly reconstituted thyrotropin-releasing hormone (TRH), reconstituted TRH that had been previously frozen, or thyrotropin (TSH) to 10 mature dogs (6 Greyhounds and 4 mixed-breed dogs). Thyrotropin-releasing hormone (0.1 mg/kg) or TSH (5 U/dog) was administered IV; venous blood samples were collected before and 6 hours after administration of TRH or TSH. Concentrations of the T4 and T3 were similar (P greater than 0.05) in serum after administration of freshly reconstituted or previously frozen TRH, indicating that TRH can be frozen at -20 C for at least 1 week without a loss in potency. Concentrations of T4, but not T3, were higher after the administration of TSH than they were after the administration of TRH (P less than 0.01). Concentrations of T4 increased at least 3-fold in all 10 dogs given TSH, whereas a 3-fold increase occurred in 7 of 10 dogs given freshly reconstituted or previously frozen TRH. Concentrations of T4 did not double in 1 dog given freshly reconstituted TRH and in 1 dog given previously frozen TRH. Concentrations of T3 doubled in 5 of 10, 2 of 10, and 5 of 10 dogs given TSH, freshly reconstituted TRH, or previously frozen TRH, respectively. Results suggested that concentrations of serum T4 are higher 6 hours after the administration of TSH than after administration of TRH, using dosage regimens of 5 U of TSH/dog or 0.1 mg of TRH/kg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of sulfamethoxazole-trimethoprim on thyroid function in dogs

OBJECTIVE: To evaluate effects of trimethoprim-sulfamethoxazole (T/SMX) on thyroid function in dogs. ANIMALS: 6 healthy euthyroid dogs. PROCEDURE: Dogs were administered T/SMX (14.1 to 16 mg/kg, PO, q 12 h) for 3 weeks. Blood was collected weekly for 6 weeks for determination of total thyroxine (TT4), free thyroxine (fT4), and canine thyroid-stimulating hormone (cTSH) concentrations. Schirmer tear tests were performed weekly. Blood was collected for CBC prior to antimicrobial treatment and at 3 and 6 weeks. RESULTS: 5 dogs had serum TT4 concentrations equal to or less than the lower reference limit, and 4 dogs had serum fT4 less than the lower reference limit after 3 weeks of T/SMX administration; cTSH concentrations were greater than the upper reference limit in 4 dogs. All dogs had TT4 and fT4 concentrations greater than the lower reference limit after T/SMX administration was discontinued for 1 week, and cTSH concentrations were less than reference range after T/SMX administration was discontinued for 2 weeks. Two dogs developed decreased tear production, which returned to normal after discontinuing administration. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that administration of T/SMX at a dosage of 14.1 to 16 mg/kg, PO, every 12 hours for 3 weeks caused decreased TT4 and fT4 concentrations and increased cTSH concentration, conditions that would be compatible with a diagnosis of hypothyroidism. Therefore, dogs should not have thyroid function evaluated while receiving this dosage of T/SMX for >2 weeks. These results are in contrast to those of a previous study of trimethoprim-sulfadiazine.     

Use of ephedrine and dopamine in dogs for the management of hypotension in routine clinical cases under isoflurane anesthesia

OBJECTIVE: To determine the cardiovascular responses of ephedrine and dopamine for the management of presurgical hypotension in anesthetized dogs. STUDY DESIGN: Prospective, randomized, clinical trial. ANIMALS: Twelve healthy client-owned dogs admitted for orthopedic surgery; six per group METHODS: Prior to surgery, 58 anesthetized dogs were monitored for hypotension [mean arterial pressure (MAP) <60 mmHg] that was not associated with bradycardia or excessive anesthetic depth. Ephedrine (0.2 mg kg(-1), IV) or dopamine (5 microg kg(-1) minute(-1), IV) was randomly assigned for treatment in 12 hypotensive dogs. Ten minutes after the first treatment (Tx(1)-10), ephedrine was repeated or the dopamine infusion rate was doubled. Cardiovascular assessments taken at baseline, Tx(1)-10, and 10 minutes following treatment adjustment (Tx(2)-10) were compared for differences within and between treatments (p < 0.05). RESULTS: Ephedrine increased cardiac index (CI), stroke volume index (SVI), oxygen delivery index (DO(2)I), and decreased total peripheral resistance (TPR) by Tx(1)-10, while MAP increased transiently (<5 minutes). The second ephedrine bolus produced no further improvement. Dopamine failed to produce significant changes at 5 microg kg(-1) minute(-1), while 10 microg kg(-1) minute(-1) increased MAP, CI, SVI significantly from baseline, and DO(2)I compared with Tx(1)-10. The improvement in CI, SVI, and DO(2)I was not significantly different between treatments at Tx(2)-10. CONCLUSIONS AND CLINICAL RELEVANCE: In anesthetized hypotensive dogs, ephedrine and dopamine improved cardiac output and oxygen delivery. However, the pressure-elevating effect of ephedrine is transient, while an infusion of dopamine at 10 microg kg(-1) minute(-1) improved MAP significantly by additionally maintaining TPR.     

Pharmacokinetics of selamectin following intravenous,oral and topical administration in cats and dogs

The pharmacokinetics of selamectin were evaluated in cats and dogs, following intravenous (0.05, 0.1 and 0.2 mg/kg), topical (24 mg/kg) and oral (24 mg/kg) administration. Following selamectin administration, serial blood samples were collected and plasma concentrations were determined by high performance liquid chromatography (HPLC). After intravenous administration of selamectin to cats and dogs, the mean maximum plasma concentrations and area under the concentration-time curve (AUC) were linearly related to the dose, and mean systemic clearance (Clb) and steady-state volume of distribution (Vd(ss)) were independent of dose. Plasma concentrations after intravenous administration declined polyexponentially in cats and biphasically in dogs, with mean terminal phase half-lives (t(1/2)) of approximately 69 h in cats and 14 h in dogs. In cats, overall Clb was 0.470 +/- 0.039 mL/min/kg (+/-SD) and overall Vd(ss) was 2.19 +/- 0.05 L/kg, compared with values of 1.18 +/- 0.31 mL/min/kg and 1.24 +/- 0.26 L/kg, respectively, in dogs. After topical administration, the mean C(max) in cats was 5513 +/- 2173 ng/mL reached at a time (T(max)) of 15 +/- 12 h postadministration; in dogs, C(max) was 86.5 +/- 34.0 ng/mL at T(max) of 72 +/- 48 h. Bioavailability was 74% in cats and 4.4% in dogs. Following oral administration to cats, mean C(max) was 11,929 +/- 5922 ng/mL at T(max) of 7 +/- 6 h and bioavailability was 109%. In dogs, mean C(max) was 7630 +/- 3140 ng/mL at T(max) of 8 +/- 5 h and bioavailability was 62%. There were no selamectin-related adverse effects and no sex differences in pharmacokinetic parameters. Linearity was established in cats and dogs for plasma concentrations up to 874 and 636 ng/mL, respectively. Pharmacokinetic evaluations for selamectin following intravenous administration indicated a slower elimination from the central compartment in cats than in dogs. This was reflected in slower clearance and longer t(1/2) in cats, probably as a result of species-related differences in metabolism and excretion. Inter-species differences in pharmacokinetic profiles were also observed following topical administration where differences in transdermal flux rates may have contributed to the overall differences in systemic bioavailability.     

Effects of anesthesia, surgery, and intravenous administration of fluids on plasma antidiuretic hormone concentrations in healthy dogs

OBJECTIVE: To evaluate effects of anesthesia, surgery, and intravenous administration of fluids on plasma concentrations of antidiuretic hormone (ADH), concentration of total solids (TS), PCV, arterial blood pressure (BP), plasma osmolality, and urine output in healthy dogs. ANIMALS: 22 healthy Beagles. PROCEDURE: 11 dogs did not receive fluids, and 11 received 20 ml of lactated Ringer's solution/kg of body weight/h. Plasma ADH adn TS concentrations, PCV, osmolality, and arterial BP were measured before anesthesia (T0) and after administration of preanesthetic agents (T1), induction of anesthesia (T2), and 1 and 2 hours of surgery (T3 and T4, respectively). Urine output was measured at T3 and T4. RESULTS: ADH concentrations increased at T1, T3, and T4, compared with concentrations at T0. Concentration of TS and PCV decreased at all times after administration of preanesthetic drugs. Plasma ADH concentration was less at T3 in dogs that received fluids, compared with those that did not. Blood pressure did not differ between groups, and osmolality did not increase > 1% from To value at any time. At T4, rate of urine production was less in dogs that did not receive fluids, compared with those that did. CONCLUSIONS AND CLINICAL RELEVANCE: Plasma ADH concentration increased and PCV and TS concentration decreased in response to anesthesia and surgery. Intravenous administration of fluids resulted in increased urine output but had no effect on ADH concentration or arterial BP. The causes and effects of increased plasma ADH concentrations may affect efficacious administration of fluids during the perioperative period in dogs.     

Effects of oral isosorbide and glycerol on intraocular pressure,serum osmolality,and blood glucose in normal dogs

Objective To evaluate and compare the effects of oral isosorbide and glycerol on intraocular pressure (IOP), serum osmolality (SOSM), and blood glucose (BG) in normal dogs. Methods Ten normal dogs were administered an oral dose of either isosorbide (1.5 g/kg), glycerol (1.5 g/kg) or control (water, 2 mL/kg) in a double blind protocol. Prior to dosing, baseline IOP, SOSM, and BG were measured in all dogs. IOP was subsequently evaluated every 30 min for 6 h post‐dosing. BG and SOSM were reassessed at times 1, 2, 4, and 6 h post‐dosing. After 1‐week washout periods, every dog was subject to each of the three treatments. The dogs were held NPO for 4 h after dosing. Results The maximal decrease in IOP was 17% by 1 h and 13.5% by 30 min after glycerol and isosorbide administration, respectively. However, the overall changes in IOP were not significant when compared to the controls. SOSM increased above baseline after dosing with glycerol but decreased after isosorbide, which difference was significant at 1, 2, and 4 h post‐administration. BG significantly increased after administration of glycerol relative to the control but was not significantly affected by isosorbide. Conclusions Neither glycerol nor isosorbide significantly affected IOP when compared to the control. However, glycerol induced significant elevations in both BG relative to the control and SOSM relative to isosorbide.     

Sedative and cardiopulmonary effects of medetomidine hydrochloride and xylazine hydrochloride and their reversal with atipamezole hydrochloride in calves

OBJECTIVE: To assess the sedative and cardiopulmonary effects of medetomidine and xylazine and their reversal with atipamezole in calves. ANIMALS: 25 calves. PROCEDURES: A 2-phase (7-day interval) study was performed. Sedative characteristics (phase I) and cardiopulmonary effects (phase II) of medetomidine hydrochloride and xylazine hydrochloride administration followed by atipamezole hydrochloride administration were evaluated. In both phases, calves were randomly allocated to receive 1 of 4 treatments IV: medetomidine (0.03 mg/kg) followed by atipamezole (0.1 mg/kg; n = 6), xylazine (0.3 mg/kg) followed by atipamezole (0.04 mg/kg; 7), medetomidine (0.03 mg/kg) followed by saline (0.9% NaCl; 6) solution (10 mL), and xylazine (0.3 mg/kg) followed by saline solution (10 mL; 6). Atipamezole or saline solution was administered 20 minutes after the first injection. Cardiopulmonary variables were recorded at intervals for 35 minutes after medetomidine or xylazine administration. RESULTS: At the doses evaluated, xylazine and medetomidine induced a similar degree of sedation in calves; however, the duration of medetomidine-associated sedation was longer. Compared with pretreatment values, heart rate, cardiac index, and PaO(2) decreased, whereas central venous pressure, PaCO(2), and pulmonary artery pressures increased with medetomidine or xylazine. Systemic arterial blood pressures and vascular resistance increased with medetomidine and decreased with xylazine. Atipamezole reversed the sedative and most of the cardiopulmonary effects of both drugs. CONCLUSIONS AND CLINICAL RELEVANCE: At these doses, xylazine and medetomidine induced similar degrees of sedation and cardiopulmonary depression in calves, although medetomidine administration resulted in increases in systemic arterial blood pressures. Atipamezole effectively reversed medetomidine- and xylazine-associated sedative and cardiopulmonary effects in calves.     

Cardiopulmonary effects of medetomidine, oxymorphone, or butorphanol in selegiline-treated dogs

OBJECTIVES: To determine if chronic selegiline HCl administration affects the cardiopulmonary response to medetomidine, oxymorphone, or butorphanol in dogs. STUDY DESIGN: Prospective randomized experimental study. ANIMALS: Twenty-eight adult, random source, hound dogs weighing 21-33 kg. METHODS: Dogs were assigned to the following treatment groups: selegiline + medetomidine (MED; n = 6); placebo + MED (n = 6), selegiline + oxymorphone (OXY; n = 6); placebo + OXY (n = 6); selegiline + butorphanol (BUT; n = 7) or placebo + BUT (n = 6). Nine dogs were treated with two of the three pre-medicants. Dogs were treated with selegiline (1 mg kg(-1) PO, q 24 hours) or placebo for at least 44 days prior to pre-medicant administration. On the day of the experiment, arterial blood for blood gas analysis, blood pressure measurements, ECG, cardiac ultrasound (mM-mode, 2-D, and continuous wave Doppler), and behavioral observations were obtained by blinded observers. An IV injection of MED (750 micro g m(-2)), OXY (0.1 mg kg(-1)) or BUT (0.4 mg kg(-1)) was given. Cardiopulmonary and behavioral data were collected at 1, 2, 5, 15, 30, and 60 minutes after injection. RESULTS: Selegiline did not modify responses to any of the pre-medicant drugs. Medetomidine caused a significant decrease in heart rate (HR), cardiac output (CO), and fractional shortening (FS). Mean arterial pressure (MAP), systemic vascular resistance (SVR), and central venous pressure (CVP) were increased. Level of consciousness and resistance to restraint were both decreased. Oxymorphone did not affect MAP, CO, CVP, or SVR, but RR and PaCO(2) were increased. Level of consciousness and resistance to restraint were decreased. BUT decreased heart rate at 1 and 5 minutes. All other cardiovascular parameters were unchanged. BUT administration was associated with decreased arterial pH and increased PaCO(2). BUT decreased level of consciousness and resistance to restraint. CONCLUSIONS AND CLINICAL RELEVANCE: Although pre-medicants themselves altered cardiopulmonary and behavioral function, selegiline did not affect the response to medetomidine, oxymorphone, or butorphanol in this group of normal dogs.     

Hematologic and serum biochemical effects of long-term administration of anti-inflammatory doses of prednisone in dogs.

Results of routine hematologic and serum biochemical analyses from 12 healthy adult male dogs that were given prednisone (0.55 mg/kg of body weight, PO, q 12 h) for 35 days were compared with those of a control group of 6 dogs that were given gelatin capsules. Analyses were performed at 2-week intervals during and after prednisone administration. Lymphocyte and eosinophil counts were significantly (P less than 0.005) decreased after 2 and 4 weeks of prednisone treatment, compared with controls. Two weeks after treatment, eosinophil counts in prednisone-treated dogs were similar to those of control dogs, whereas lymphocyte counts remained low 4 weeks after treatment in treated dogs (1,869 +/- 145 cells/microliters), compared with that in control dogs (3,662 +/- 548 cells/microliters). Neutrophil and monocyte counts did not significantly change during glucocorticoid administration. Mean platelet volume significantly (P less than 0.001) decreased after 4 weeks of prednisone treatment, but returned to pretreatment values by 2 weeks after treatment. Four weeks of prednisone treatment did not cause significant increased activity in serum alanine transaminase, total alkaline phosphatase or the steroid-induced isoenzyme of alkaline phosphatase. Significant increases in serum albumin (P less than 0.001) and total protein (P less than 0.05) concentrations were detected after 4 weeks of treatment, but mean values were not significantly different from those of controls 2 weeks after treatment ended. Results of our study indicate that eosinophil and lymphocyte counts are the most sensitive indicators of long-term glucocorticoid administration at anti-inflammatory dosages of 1.1 mg/kg daily.     

Evaluation of the urodynamic and hemodynamic effects of orally administered phenylpropanolamine and ephedrine in female dogs

OBJECTIVE: To compare the urodynamic and hemodynamic effects of different dosages of phenylpropanolamine and ephedrine and determine effective dosages in increasing urethral resistance in female dogs. ANIMALS: 20 sexually intact female Beagles. PROCEDURE: Dogs were allocated into 4 groups and received phenylpropanolamine once, twice, or 3 times daily, or ephedrine twice daily, for 14 days. On days 0, 7, and 14, urethral pressure profiles were performed while dogs were anesthetized with propofol. Variables recorded included maximum urethral pressure, maximum urethral closure pressure, integrated pressure, functional profile length, anatomic profile length, plateau distance, distance before maximum urethral pressure, and maximum meatus pressure. Arterial and central venous pressures were measured before anesthetic induction and 10 and 35 minutes after induction. RESULTS: Administration of phenylpropanolamine once daily or ephedrine twice daily significantly increased maximum urethral pressure and maximum urethral closure pressure. Values for integrated pressure were significantly increased after 14 days of once-daily administration of phenylpropanolamine. Variables did not change significantly from day 7 to day 14. Diastolic and mean arterial blood pressures increased significantly during the treatment periods, and arterial pressure decreased during propofol infusion. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of phenylpropanolamine once daily or ephedrine twice daily increased urethral resistance in clinically normal dogs and may be recommended for management of urethral sphincter mechanism incompetence. Treatment efficacy may be assessed after 1 week. Dogs with concurrent cardiovascular disease should be monitored for blood pressure while receiving alpha-adrenergic agents because of the effects on diastolic and mean arterial pressure.     

Effects of perzinfotel on the minimum alveolar concentration of isoflurane in dogs

OBJECTIVE: To determine the effect of IV administration of perzinfotel on the minimum alveolar concentration (MAC) of isoflurane in dogs. Animals-6 healthy sexually intact male Beagles. PROCEDURES: Dogs were instrumented with a telemetry device that permitted continuous monitoring of heart rate, arterial blood pressure, and body temperature. Dogs were anesthetized with propofol (4 to 6 mg/kg, IV) and isoflurane for 30 minutes before determination of MAC of isoflurane. Isoflurane MAC values were determined 4 times, separated by a minimum of 7 days, before and after IV administration of perzinfotel (0 [control], 5, 10, and 20 mg/kg). Bispectral index and percentage hemoglobin saturation with oxygen (SpO(2)) were monitored throughout anesthesia. RESULTS: Isoflurane MAC was 1.32 +/- 0.14%. Intravenous administration of perzinfotel at 0, 5, 10, and 20 mg/kg decreased isoflurane MAC by 0%, 24%, 30%, and 47%, respectively. Perzinfotel significantly decreased isoflurane MAC values, compared with baseline and control values. The bispectral index typically increased with higher doses of perzinfotel and lower isoflurane concentrations, but not significantly. Heart rate, body temperature, and SpO(2) did not change, but systolic, mean, and diastolic arterial blood pressures significantly increased with decreases in isoflurane MAC after administration of perzinfotel at 10 and 20 mg/kg, compared with 0 and 5 mg/kg. CONCLUSIONS AND CLINICAL RELEVANCE: IV administration of perzinfotel decreased isoflurane MAC values. Improved hemodynamics were associated with decreases in isoflurane concentration.     

Pharmacokinetics of norfloxacin in dogs after single intravenous and single and multiple oral administrations of the drug

Norfloxacin was given to 6 healthy dogs at a dosage of 5 mg/kg of body weight IV and orally in a complete crossover study, and orally at dosages of 5, 10, and 20 mg/kg to 6 healthy dogs in a 3-way crossover study. For 24 hours, serum concentration was monitored serially after each administration. Another 6 dogs were given 5 mg of norfloxacin/kg orally every 12 hours for 14 days, and serum concentration was determined serially for 12 hours after the first and last administration of the drug. Complete blood count and serum biochemical analysis were performed before and after 14 days of oral norfloxacin administration, and clinical signs of drug toxicosis were monitored twice daily during norfloxacin administration. Urine concentration of norfloxacin was determined periodically during serum acquisition periods. Norfloxacin concentration was determined, using high-performance liquid chromatography with a limit of detection of 25 ng of norfloxacin/ml of serum or urine. Serum norfloxacin pharmacokinetic values after single IV dosing in dogs were best modeled, using a 2-compartment open model, with distribution and elimination half-lives of 0.467 and 3.56 hours (harmonic means), respectively. Area-derived volume of distribution (Vd area) was 1.77 +/- 0.69 L/kg (arithmetic mean +/- SD), and serum clearance (Cls) was 0.332 +/- 0.115 L/h/kg. Mean residence time was 4.32 +/- 0.98 hour. Comparison of the area under the curve (AUC; derived, using model-independent calculations) after iv administration (5 mg/kg) with AUC after oral administration (5 mg/kg) in the same dogs indicated bioavailability of 35.0 +/- 46.1%, with a mean residence time after oral administration of 5.71 +/-2.24 hours. Urine concentration was 33.8 +/- 15.3 micrograms/ml at 4 hours after a single dose of 5 mg/kg given orally, whereas concentration after 20 mg/kg was given orally was 56.8 +/- 18.0 micrograms/ml at 6 hours after dosing. Twelve hours after drug administration, urine concentration was 47.4 +/- 20.6 micrograms/ml after the 5-mg/kg dose and 80.6 +/- 37.7 micrograms/ml after the 20/mg/kg dose.(ABSTRACT TRUNCATED AT 250 WORDS)