Pharmacokinetics of intravenously, intramuscularly and intra-adiposely administered carazolol in pigs

Hyaluronidase administered with xylazine-tiletamine-zolazepam into adipose tissue shortens recovery from anesthesia in pigs

OBJECTIVE

To evaluate the effect of hyaluronidase on uptake, duration and speed of elimination of xylazine-tiletamine-zolazepam administered in the subcutaneous fat over the dorsal lumbar region of swine.

STUDY DESIGN

Blinded, randomized, crossover study.

ANIMALS

Six healthy Landrace/Large White pigs weighing 132±24 kg (mean±standard deviation).

METHODS

Animals were administered xylazine (1 mg kg^-1) and tiletamine-zolazepam (8 mg kg^-1) (control treatment, CON), or xylazine-tiletamine-zolazepam at the same doses with hyaluronidase (400 IU) (treatment HYA). The treatments were administered into the dorsal lumbar adipose tissue, 2.5-3.0 cm laterally from the spinous process of the second lumbar vertebra. The latency, anesthesia and recovery periods were measured. Heart rate, noninvasive systolic, diastolic, and mean arterial pressures, respiratory rate, hemoglobin oxygen saturation and rectal temperature were recorded every 10 minutes for up to 50 minutes.

RESULTS

One animal in CON and one animal in HYA were responsive to stimulation and did not allow safe handling. No significant difference was found between treatments for latency (CON 11.3±5.9 minutes, HYA 7.4±5.1 minutes) and anesthesia (CON 53±53 minutes, HYA 49±38 minutes) periods. Recovery period was shorter in HYA (9±6 minutes) than in CON (32±16 minutes) (p < 0.05). Physiological variables were not significantly changed over time and were within accepted normal clinical limits for the species in both treatments.

CONCLUSION AND CLINICAL RELEVANCE

Hyaluronidase (400 IU) administered into adipose tissue in pigs did not reduce the latency and duration of dissociative anesthesia, but was associated with faster recovery.

Sustained release veterinary parenteral products

Controlled release parenteral dosage forms have application in veterinary medicine. Systems that minimize the need for repeated injections while achieving therapeutic effects for extended periods offer benefits that make commercial development of these products desirable. While some products have already found commercial success, others will result from application of new controlled release technologies. This review highlights the formulation and technology challenges in developing some of these controlled release technologies into products. Further, examples of application of controlled release technologies in the veterinary field are discussed.

The role of adrenoreceptors in control of stereotyped oral behavior in restricted-fed fowls

Effects on environmentally induced oral stereotypies (object pecking and drinker-directed activity) of preferential antagonists and agonists of adrenoreceptor subtypes were examined in individually caged broiler breeder fowls subjected to chronic food restriction. Three drugs in each category were injected intravenously at three doses, and their effects compared with a saline control treatment. With the antagonists, object pecking was suppressed more by prazosin (alpha 1) and propranolol (beta) than by yohimbine (alpha 2), while drinker-directed activity showed delayed stimulation with yohimbine and propranolol. With the agonists, drinker-directed activity was suppressed more by clonidine (alpha 2) than by isoproterenol (beta) and phenylephrine (alpha 1), while object pecking was inhibited by the high doses of clonidine and isoproterenol but showed delayed stimulation with the low dose of clonidine and (nonsignificantly) the high dose of phenylephrine. Initial suppression of both oral stereotypies by the high doses of yohimbine and isoproterenol, and high and medium doses of clonidine, may have been due to sedation, because in those instances it coincided with increased sitting, an activity not normally seen. Increased standing with clonidine and the medium dose of yohimbine may also reflect sedation. When there were no significant increases in sitting or standing to indicate sedation, responses of both stereotypies were essentially the same with all three adrenoreceptor subtypes; i.e., object pecking was inhibited by the antagonist but not the agonist, while drinker-directed activity was inhibited by the agonist but not the antagonist. It is concluded that alpha 1, alpha 2, and beta adrenoreceptors are all implicated in expression of these stereotypes, and that the two activities may be differentially controlled.