The pharmacokinetics of enrofloxacin in adult African clawed frogs (Xenopus laevis).

Pharmacokinetics of enrofloxacin, a fluoroquinolone antibiotic, was determined in adult female Xenopus laevis after single-dose administration (10 mg/kg) by intramuscular or subcutaneous injection. Frogs were evaluated at various time points until 8 h after injection. Plasma was analyzed for antibiotic concentration levels by HPLC. We computed pharmacokinetic parameters by using noncompartmental analysis of the pooled concentrations (naive pooled samples). After intramuscular administration of enrofloxacin, the half-life was 5.32 h, concentration maximum was 10.85 µg/mL, distribution volume was 841.96 mL/kg, and area under the time-concentration curve was 57.59 µg×h/mL; after subcutaneous administration these parameters were 4.08 h, 9.76 µg/mL, 915.85 mL/kg, and 47.42 µg×h/mL, respectively. According to plasma pharmacokinetics, Xenopus seem to metabolize enrofloxacin in a manner similar to mammals: low levels of the enrofloxacin metabolite, ciprofloxacin, were detected in the frogs' habitat water and plasma. At necropsy, there were no gross or histologic signs of toxicity after single-dose administration; toxicity was not evaluated for repeated dosing. The plasma concentrations reached levels considered effective against common aquatic pathogens and suggest that a single, once-daily dose would be a reasonable regimen to consider when treating sick frogs. The treatment of sick frogs should be based on specific microbiologic identification of the pathogen and on antibiotic susceptibility testing.

Evaluation and refinement of euthanasia methods for Xenopus laevis.

The most common method of euthanasia for Xenopus species is by immersion in tricaine methane sulfonate solution (MS222). A wide range of doses of MS222 (0.5 to 5 g/L) have been recommended, but few reports describe dose-response testing, the time to loss of consciousness, or the reliability of euthanasia. The objective of this study is to evaluate the efficacy of immersing individual and groups of frogs in MS222 at concentrations ranging from 1 to 5 g/L for euthanasia and of 3 less-common methods: intracoelomic injection of MS222, intracoelomic injection of sodium pentobarbital with phenytoin, and ventral cutaneous application of benzocaine gel. Our results indicate that immersion for at least 1 h in a 5-g/L buffered solution of MS222, intracoelomic injection of 1100 mg/kg sodium pentobarbital with sodium phenytoin (equivalent to 0.3 mL solution per frog), or ventral cutaneous application of 182 mg/kg benzocaine (equivalent to a 2 cm x 1 mm of 20% benzocaine gel) is necessary to euthanize adult X. laevis and ensure complete cessation of the heartbeat without recovery. These doses are considerably higher than those previously recommended for this species.

Tacrolimus ointment: a novel and effective topical treatment of localized atopic dermatitis in a rhesus macaque (Macaca mulatta).

An adult, male, rhesus macaque presented with pruritus and a focal, exudative, inflamed, erythematous skin lesion of approximately 2 cm in diameter on the ventral aspect of the mandible. The lesion resolved after 10 d of treatment with 1% chlorhexidine solution and triple-antibiotic ointment. However, the skin lesion subsequently recurred several times over a 2-mo period. A punch biopsy was performed, and histological changes were most consistent with a diagnosis of atopic dermatitis. Treatment with topical tacrolimus ointment, an immunosuppressive drug, proved successful in the resolution of all clinical signs after 4 mo. According to a literature review, this article is the first report of the use of tacrolimus ointment as a topical treatment of atopic dermatitis in a rhesus macaque.

Refuge cover decreases the incidence of bite wounds in laboratory South African clawed frogs (Xenopus laevis).

The Guide for the Care and Use of Laboratory Animals recommends environmental enrichment for all laboratory animals, including amphibians. In this study, we evaluated the effect of adding environmental enrichment in the form of acrylonitrile- butadiene-styrene (ABS) pipes as covered refuge for laboratory Xenopus laevis housed in 2 pond-style tanks (capacity, 300 l; stocking density, approximately 150 frogs/tank; dimensions, 1.3 x 1.8 x 1.3 m). Medical records from animals housed in these 2 ponds between 1 January 2001 to 31 December 2003 revealed the incidence of bite wounds to be 5.0%, 4.0%, and 5.0% annually, respectively, and indicated 2 episodes of cannibalism (in 2003). In January 2004, we added ABS pipes as refuge housing to these tanks and continued to monitor the number of bite wounds and cannibalism. Over the following 24 mo (1 January 2004 to 1 January 2006), the incidence of bite wounds declined to 0.3% and 0.7% annually, respectively; no episodes of cannibalism were reported. The results of this investigation indicate that environmental enrichment in the form of ABS pipes for refuge cover has a quantifiable beneficial effect on the physical and social wellbeing of laboratory Xenopus laevis.