Pharmacokinetics of subcutaneous ketamine administration via the Omnipod® system in dogs.

Ketamine is an injectable anesthetic agent with analgesic and antidepressant effects that can prevent maladaptive pain. Ketamine is metabolized by the liver into norketamine, an active metabolite. Prior rodent studies have suggested that norketamine is thought to contribute up to 30% of ketamine's analgesic effect. Ketamine is usually administered as an intravenous (IV) bolus injection or continuous rate infusion (CRI) but can be administered subcutaneously (SC) and intramuscularly (IM). The Omnipod® is a wireless, subcutaneous insulin delivery device that adheres to the skin and delivers insulin as an SC CRI. The Omnipod® was used in dogs for postoperative administration of ketamine as a 1 mg/kg infusion bolus (IB) over 1 hour (h). Pharmacokinetics (PK) showed plasma ketamine concentrations between 42 and 326.1 ng/mL. The median peak plasma concentration was 79.5 (41.9-326.1) ng/mL with a Tmax of 60 (30-75) min. After the same infusion bolus, the corresponding norketamine PK showed plasma drug concentrations between 22.0 and 64.8 ng/mL. The median peak plasma concentration was 43.0 (26.1-71.8) ng/mL with a median Tmax of 75 min. The median peak ketamine plasma concentration exceeded 100 ng/mL in dogs for less than 1 h post infusion. The Omnipod® system successfully delivered subcutaneous ketamine to dogs in the postoperatively.

Evaluation of construct and criterion validity for the 'Liverpool Osteoarthritis in Dogs' (LOAD) clinical metrology instrument and comparison to two other instruments.

OBJECTIVE: To test the 'Liverpool Osteoarthritis in Dogs' (LOAD) questionnaire for construct and criterion validity, and to similarly test the Helsinki Chronic Pain Index (HCPI) and the Canine Brief Pain Inventory (CBPI). DESIGN: Prospective Study. ANIMALS: 222 dogs with osteoarthritis. PROCEDURE: Osteoarthritis was diagnosed in a cohort of dogs on the basis of clinical history and orthopedic examination. Force-platform analysis was performed and a "symmetry index" for peak vertical force (PVF) was calculated. Owners completed LOAD, CBPI and HCPI instruments. As a test of construct validity, inter-instrument correlations were calculated. As a test of criterion validity, the correlations between instrument scores and PVF symmetry scores were calculated. Additionally, internal consistency of all instruments was calculated and compared to those previously reported. Factor analysis is reported for the first time for LOAD, and is compared to that previously reported for CBPI and HCPI. RESULTS: Significant moderate correlations were found between all instruments, implying construct validity for all instruments. Significant weak correlations were found between LOAD scores and PVF symmetry index, and between CBPI scores and PVF symmetry index. CONCLUSION AND CLINICAL RELEVANCE: LOAD is an owner-completed clinical metrology instrument that can be recommended for the measurement of canine osteoarthritis. It is convenient to use, validated and, as demonstrated here for the first time, has a correlation with force-platform data.