The safety of high-dose buprenorphine administered subcutaneously in cats.

The safety of a proprietary formulation of buprenorphine hydrochloride administered subcutaneously (SC) to young cats was investigated in a blinded, randomized study. Four cohorts of eight cats aged approximately 4 months were administered saline, 0.24, 0.72 or 1.20 mg/kg/day buprenorphine SC for nine consecutive days, representing 0×, 1×, 3× and 5× of the intended dose. Cats were monitored daily for evidence of clinical reactions, food and water intake and adverse events (AEs). Physical examinations, clinical pathology, vital signs and electrocardiograms (ECGs) were evaluated at protocol-specified time points. Complete necropsy and histopathologic examinations were performed following humane euthanasia. Four buprenorphine-treated cats experienced AEs during the study, two unrelated and two related to study drug administration. The two cats with AEs considered related to drug administration had clinical signs of hyperactivity, difficulty in handling, disorientation, agitation and dilated pupils in one 0.24 mg/kg/day cat and one 0.72 mg/kg/day cat. All of these clinical signs were observed simultaneously. There were no drug-related effects on survival, injection response, injection site inspections, body weight, food or water consumption, bleeding time, urinalysis, respiration rate, heart rate, ECGs, blood pressures, body temperatures, macroscopic examinations or organ weights. Once daily buprenorphine s.c. injections at doses of 0.24, 0.72 and 1.20 mg/kg/day for 9 consecutive days were well tolerated in young domestic cats.

General pharmacology of [2,2-dimethyl-6-(4-chlorophenyl)-7-phenyl-2,3- dihydro-1H-pyrrolizine-5-yl]-acetic acid in experimental animals.

[2,2-Dimethyl-6-(4-chlorophenyl)-7-phenyl-2,3-dihydro-1H-pyrrolizine-5- yl]-acetic acid (ML 3000) is a newly synthesized compound with analgesic, antipyretic and anti-inflammatory activity. The general pharmacological effects of ML 3000 following oral administration were investigated in experimental animals. The results showed that with regard to the CNS, ML 3000 did not affect behaviour in the Irwin test, locomotor activity or hexobarbital-induced sleep at doses of 30, 100 and 300 mg/kg. ML 3000, at a single dose of 100 mg/kg administered intraduodenally, had no notable effect on the cardiovascular system or respiration in anaesthestised rats and dogs nor on neuromuscular function in anaesthetised cats. No evidence of gastric damage or disturbance of peristalsis was observed following oral administration of ML 3000. In vitro, ML 3000 evoked a weak spasmogenic response in the guinea-pig ileum with a dose-related inhibition of acetylcholine, histamine and barium chloride-induced responses. A small transient reduction in urine volume was observed after the highest dose accompanied by decreases in electrolyte excretion at doses of 100 and 300 mg/kg in rats. The results demonstrate that ML 3000 has no notable general pharmacological effects under the experimental conditions reported.

Acute and chronic anti-inflammatory properties of [2,2-dimethyl-6-(4- chlorophenyl)-7-phenyl-2,3-dihydro-1H-pyrrolizine-5-yl]-acetic acid.

The carrageenan-induced paw oedema in the rat was chosen as the experimental model for acute antiphlogistic activity. ED50 values of 3 mg/kg p.o. for indometacin and of 17 mg/kg p.o. for [2,2-dimethyl-6-(4-chlorophenyl)-7-phenyl-2, 3-dihydro-1H-pyrrolizine-5-yl]-acetic acid (ML 3000) at calculated plasma levels (micrograms/ml) of approximately 5.0 and 20.0 were recorded for indometacin and ML 3000, respectively. The activity ratio of indometacin: ML 3000 is therefore about 1:6 with regard to the oral dose and about 1:4 with regard to the calculated plasma level. Indometacin is more potent than ML 3000 on the one hand, but on the other hand ML 3000 is better tolerated by the stomach in this experimental study: the ulcerogenic dose UD50 (indometacin) is 7 mg/kg p.o., whereas ML 3000 is tolerated well up to the highest tested dose of 100 mg/kg p.o. The adjuvant arthritis in the rat served as the model for chronic antiphlogistic activity. ML 3000 at doses of 20 mg/kg/d p.o. and higher, and indometacin at a dosage of 2 mg/kg/d p.o. produced a similar rate of reduction of the adjuvant-induced secondary lesions and paw swelling of the injected and uninjected paws, following prophylactic as well as therapeutic treatment with the compounds.

Gastrointestinal tolerance of [2,2-dimethyl-6-(4-chlorophenyl-7-phenyl- 2,3-dihydro-1H-pyrrolizine-5-yl]-acetic acid in the rat.

The gastrointestinal tolerance of [2,2-dimethyl-6-(4-chlorophenyl)-7- phenyl-2,3-dihydro-1H-pyrrolizine-5-yl]-acetic acid (ML 3000, CAS 156897-06-2) has been tested in comparison with indometacin, after both single and multiple administrations for 5 and 11 days in an in vivo rat assay. A single oral administration of ML 3000 at doses of 10, 30 and 100 mg/kg produced no gastrointestinal damage. Repeated oral administration of ML 3000 at daily doses of 10, 30 and 100 mg/kg produced slight gastrointestinal damage, but the effect was minimal and was not found to be statistically significant. Indometacin produced highly statistically significant gastric and duodenal damage following one single administration of 10 mg/kg. Repeated oral administration, at 3 mg/kg each day, produced moderate and statistically significant gastric and slight duodenal damage on Day 5 of dosing. However, by Day 11 pronounced duodenal damage was observed which was shown to be statistically highly significant. These results indicate that ML 3000 is clearly better tolerated by the gastrointestinal tract than indometacin after single and multiple administration up to 11 days in rats.