Comparative pharmacokinetics and a clinical laboratory evaluation of intravenous acetaminophen in Beagle and Galgo Español dogs.

OBJECTIVE: To assess the pharmacokinetics (PK) and conduct a clinical laboratory evaluation of acetaminophen in Beagle and Galgo Español (GE) dogs. STUDY DESIGN: Prospective randomized experimental trial. ANIMALS: A total of 20 healthy dogs - 10 Beagles and 10 GE (six males and four females in both groups). METHODS: Acetaminophen (10 and 20 mg kg-1) was administered intravenously (IV) to the dogs on two different occasions. Plasma concentrations were analysed by high-performance liquid chromatography. PK analysis was undertaken using compartmental modelling with ADAPT 5 software. Simulations after multiple IV doses were investigated. Clinical laboratory values such as red blood cell (RBC) count, haemoglobin (Hb), haematocrit (Ht), white blood cell (WBC) count, platelet count, total proteins, alanine aminotransferase (ALT), aspartate aminotransferase, urea and creatinine were measured before and 24 hours after acetaminophen administration in combination with clinical examination to assess side effects resulting from the drug. RESULTS: A two-compartmental model best described time-concentration profiles of acetaminophen. PK parameters were different as a result of a breed effect. For doses of 10 and 20 mg kg-1, respectively, clearance values were 1.70 (1.15-2.27) and 1.62 (1.06-2.86) L kg-1 hour-1 for Beagles and 1.18 (0.70-1.39) and 1.08 (0.67-1.35) L kg-1 hour-1 for GE; elimination half-life values were 2.64 (0.52-4.46) and 2.86 (0.87-4.63) hours for Beagles and 3.49 (1.89-7.80) and 4.57 (2.08-8.90) hours for GE. Significant differences were also found between GE and Beagles in the RBC count, Ht, Hb, WBC count and serum ALT before drug administration, and these differences were maintained 24 hours later, independent of the dosage used. For each breed, no side effects resulting from IV acetaminophen administration were observed at doses of either 10 or 20 mg kg-1. CONCLUSIONS AND CLINICAL RELEVANCE: IV PK of acetaminophen was different between Beagles and GE dogs. Side effects were not detected. Further studies are necessary to evaluate the PK in a clinical context.

Modulation of acute transient exercise-induced hypertension after oral administration of four angiotensin-converting enzyme inhibitors in normotensive horses.

Changes in blood pressure (BP) during acute hypertension in response to angiotensin-converting enzyme inhibitors (ACEIs) have not been investigated in normotensive horses. In this study, six healthy horses were subjected to five trials, consisting in a treadmill exercise workload of 8 m/s for 1 min, 2 h after oral administration (PO) of placebo (0 mg/kg), enalapril (2.0 mg/kg), quinapril (1.0 mg/kg), ramipril (0.2 mg/kg) or benazepril (0.5 mg/kg). Serum angiotensin converting enzyme (ACE) activity was measured and systolic (SBP) and diastolic (DBP) blood pressures were recorded at rest (R), 2 h after placebo or ACEI administration (pre-E) and within the first 20 s after exercise (post-E). Mean maximum serum ACE inhibition 2 h after PO administration was 4.8% (placebo), 39.4% (enalapril), 46.4% (quinapril), 55.0% (ramipril) and 71.68% (benazepril). There were no significant differences in serum ACE inhibition between enalapril and quinapril. SBP and DBP at times R and pre-E were not different in any of the five trials. In response to exercise, SBP increased by 67.6% (placebo), 52.7% (enalapril), 43.1% (quinapril), 26.6% (ramipril) and 4.2% (benazepril). In response to exercise, DBP increased by 20.6, 13.2, 11.7, 16.6 and 3.7% after placebo, enalapril, quinapril, ramipril and benazepril administration, respectively. Serum ACE activity changed during exercise, but statistical significance was not achieved. In conclusion, administration of PO benazepril at a dose of 0.5 mg/kg modulated physiological hypertension induced by exercise in horses that were otherwise normotensive.