Assessment of absorption of transdermal ondansetron in normal research cats.

Objectives The objective of this study was to assess the absorption of transdermal ondansetron in healthy cats. Methods Five research cats with unremarkable complete blood count, biochemistry and urinalysis were used for both single- and multiple-dose application studies. For single-dose application, 4 mg ondansetron in 0.1 ml Lipoderm gel was applied once to the internal ear pinna. Blood samples were collected via jugular catheter over a 48 h period following administration (0, 15 mins, 30 mins, 1 h, 2 h, 4 h, 8 h, 12 h, 24 h and 48 h). For multiple-dose application, 4 mg ondansetron in 0.1 ml Lipoderm gel was applied for five consecutive days before blood samples were obtained in the same manner. Serum was separated and frozen prior to analysis. Ondansetron was measured via liquid chromatography coupled to tandem mass spectrometry. Results Analysis revealed no clinically relevant drug levels in serum after either single- or multiple-dose administration of 4 mg transdermal ondansetron. Conclusions and relevance Transdermal application of 4 mg ondansetron does not result in clinically relevant serum concentrations of drug. Despite characteristics of the drug that imply suitability for transdermal application, this does not appear to be an acceptable method of drug delivery for this medication at this dose. This study highlights the importance of assessing the suitability of each medication for transdermal administration.

Comparison of proliferative and immunomodulatory potential of adipose-derived mesenchymal stem cells from young and geriatric cats.

Objectives The objective of this study was to compare the ability of adipose-derived mesenchymal stem cells (aMSCs) generated from young vs geriatric cats to proliferate in culture, suppress lymphocyte proliferation and undergo senescence. Methods Adipose tissues from five young (<5 years) and six geriatric (>10 years) cats were harvested and cryopreserved for subsequent aMSC isolation and culture. aMSC proliferation in culture was compared via determination of time until passage two and by 3-(4,5-demethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The immunomodulatory capacity of aMSCs was assessed using lymphocyte proliferation assays, and senescence was evaluated using senescence-associated B-galactosidase (SABG) expression. All assays were performed on aMSCs between passage two and passage three. Results aMSCs from geriatric cats took significantly longer ( P = 0.008) to reach passage two (median 11 days, range 9-22 days) compared with aMSCs from young healthy cats (median 7 days, range 6-8 days). No significant difference was detected between young and geriatric cats in terms of their ability to suppress lymphocyte proliferation. SABG expression was not significantly different between young and geriatric aMSCs. Conclusions and relevance Compared with young feline aMSCs, geriatric aMSCs are significantly impaired in their ability to rapidly proliferate to passage two following initial culture, presenting a concern for autologous therapy. Nonetheless, once the cells are expanded, young and geriatric cat aMSCs appear to be equivalent in terms of their ability to functionally suppress T-cell activation and proliferation.

Drug exposure and clinical effect of transdermal mirtazapine in healthy young cats: a pilot study.

Objectives The objective of this study was to measure drug exposure and clinical effects after administration of transdermal mirtazapine (TMZ) in healthy cats. Methods Phase I: seven healthy research cats received (1) 3.75 mg and 7.5 mg TMZ once aurally with 48 h serum sampling (serum samples were obtained via the jugular catheter at 0, 0.5, 1, 2, 5, 9, 12, 24, 36 and 48 h); (2) 7.5 mg TMZ and placebo daily aurally for 6 days then 48 h serum sampling; (3) 1.88 mg mirtazapine orally once with serum sampling at 1, 4 and 8 h. Phase II: 20 client-owned cats were enrolled in a randomized, double-blind, placebo-controlled, three-way crossover clinical effect study. Treatments consisted of 6 days of aural 7.5 mg TMZ or placebo gel at home, and 1.88 mg mirtazapine orally once in the clinic. Owners documented appetite, rate of food ingestion, begging activity and vocalization daily at home. On day 6, food consumed, activity and vocalization were documented in hospital, and trough and peak serum mirtazapine levels were obtained. Serum mirtazapine and gel concentrations were measured using liquid chromatography/tandem mass spectrometry. Results Phase I: administration of TMZ achieved measureable serum mirtazapine concentrations. Area under the curve0-48 of multidose 7.5 mg TMZ was significantly higher than single-dose 1.88 mg oral mirtazapine (OMZ) ( P = 0.02). Phase II: client-owned cats administered TMZ had a significant increase in appetite ( P = 0.003), rate of food ingestion ( P = 0.002), activity ( P = 0.002), begging ( P = 0.002) and vocalization ( P = 0.002) at home. In hospital there was a significant increase in food ingested with both TMZ and OMZ compared with placebo ( P <0.05). Gel concentrations ranged from 87%-119% of target dose. Conclusions and relevance TMZ 7.5 mg daily achieves measureable serum concentrations and produces significant appetite stimulation despite variance in compounded gel concentrations, but side effects denote a lower dose is indicated.