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Bizley SC, Dudhia J, Smith RKW, Williams AC. Transdermal drug delivery in horses: An in vitro comparison of skin structure and permeation of two model drugs at various anatomical sites. Vet Dermatol 2023. [PMID: 37185892 DOI: 10.1111/vde.13162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/10/2023] [Accepted: 03/28/2023] [Indexed: 05/17/2023]
Abstract
BACKGROUND Oral and parenteral drug delivery in horses can be difficult. Equine-specific transdermal drug formulations offer improved ease of treatment; development of such formulations requires a deeper understanding of the structural and chemical tissue barrier of horse skin. HYPOTHESIS/OBJECTIVES To compare the structural composition and barrier properties of equine skin. ANIMALS Six warmblood horses (two males, four females) with no skin diseases. MATERIALS AND METHODS Routine histological and microscopic analyses were carried out with image analysis for skin from six different anatomical locations. In vitro drug permeation was analysed using a standard Franz diffusion cell protocol coupled with reversed phase-high-performance liquid chromatography detailing flux, lag times and tissue partitioning ratios of two model drug compounds. RESULTS Epidermal and dermal thicknesses varied between sites. The dermal and epidermal thicknesses of the croup were 1764 ± 115 μm and 36 ± 3.6 μm, respectively, and were significantly different (p < 0.05) from the inner thigh thicknesses which were 824 ± 35 μm and 49 ± 3.6 μm. Follicular density and size also varied. The highest flux for the model hydrophilic molecule (caffeine) was for the flank (3.22 ± 0.36 μg/cm2 /h), while that for the lipophilic molecule (ibuprofen) was for the inner thigh (0.12 ± 0.02 μg/cm2 /h). CONCLUSIONS AND CLINICAL RELEVANCE Anatomical location differences in equine skin structure and small molecule permeability were demonstrated. These results can aid in the development of transdermal therapies for horses.
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Affiliation(s)
- Samuel C Bizley
- Clinical Science and Services, The Royal Veterinary College, Hatfield, Hertfordshire, UK
| | - Jayesh Dudhia
- Clinical Science and Services, The Royal Veterinary College, Hatfield, Hertfordshire, UK
| | - Roger K W Smith
- Clinical Science and Services, The Royal Veterinary College, Hatfield, Hertfordshire, UK
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Beuve MS, Espana B, Pin D, Prouillac C. Ex-vivo study of the percutaneous absorption of a tramadol formulation through feline inner pinna skin. Res Vet Sci 2022; 151:57-63. [PMID: 35868201 DOI: 10.1016/j.rvsc.2022.05.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 04/28/2022] [Accepted: 05/16/2022] [Indexed: 10/17/2022]
Abstract
OBJECTIVES Oral medication of small animals, particularly cats, is often challenging. The transdermal route may provide an easier option for owners to administer chronic treatment. Tramadol is an analgesic mainly used in humans; it is also commonly used in dogs, despite some controversy over its clinical efficacy. Recent studies have suggested that tramadol is efficacious for pain management in cats. In cats, the inner pinna is the most commonly used site for transdermal drug therapy; the use of this site has been validated in experimental studies of methimazole and mirtazapine treatment. This ex vivo study aimed to characterise the percutaneous absorption pharmacokinetics of a formulation of tramadol in Pentravan through feline inner pinna skin. METHODS High-performance liquid chromatography was used to assess the stability of the tramadol formulation (100 mg/ml in Pentravan) over three months at room temperature. Forced degradation was also assessed in neutral, acidic, alkaline, and oxidative conditions. A Franz cell system was employed to evaluate percutaneous absorption of a finite dose of tramadol. RESULTS The tramadol formulation was stable for three months at room temperature. Tramadol penetrated through ex vivo feline inner pinna skin, but considerable intra- and inter-individual variability in kinetics was observed. Comparison with another vehicle, Lipoderm, revealed no significant difference in the percutaneous absorption of tramadol. CONCLUSIONS AND RELEVANCE The Pentravan formulation assessed in this study supported tramadol absorption across the feline inner ear skin. In vivo studies are necessary to evaluate the pharmacokinetics and efficacy of this formulation.
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Affiliation(s)
| | | | - Didier Pin
- Université de Lyon, VetAgro Sup, Marcy l'Etoile, France
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Quimby JM, Benson KK, Summers SC, Saffire A, Herndon AK, Bai S, Gustafson DL. Assessment of compounded transdermal mirtazapine as an appetite stimulant in cats with chronic kidney disease. J Feline Med Surg 2019; 22:376-383. [PMID: 31161850 PMCID: PMC7099811 DOI: 10.1177/1098612x19851303] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Objectives The aim of this study was to assess the appetite stimulation properties of
compounded transdermal mirtazapine (CTM) in cats with chronic kidney disease
(CKD). Methods Two sequential double-blind placebo-controlled crossover prospective studies
were performed in client-owned cats with stable stage 2 or 3 CKD and a
history of decreased appetite. In the first study nine CKD cats were
randomized to receive 3.75 mg/0.1 ml CTM gel or placebo on the inner pinna
every other day for 3 weeks, then, after a 4 day washout period, the cats
were crossed over to the alternate 3 week treatment. In a second study, 10
CKD cats were randomized to receive 1.88 mg/0.1 ml CTM or placebo on the
same schedule. Physical examination and serum biochemistry were performed
before and after each treatment period, and owners kept daily logs of
appetite, activity and eating behaviors. Mirtazapine concentrations in CTM
gels and steady-state mirtazapine serum concentrations were measured using
liquid chromatography/tandem mass spectrometry. Results Administration of both 3.75 mg and 1.88 mg CTM resulted in a statistically
significant increase in weight (P = 0.002 for both),
increase in appetite (P = 0.01 and P =
0.005, respectively), and increase in rate of food consumption
(P = 0.03 and P = 0.008,
respectively). No significant difference in activity or vocalization was
seen at either dose; however, individual cats experienced excessive meowing.
Median weight increase for the 3.75 mg arm was 0.22 kg (range 0.04–0.44 kg),
while median weight increase for the 1.88 mg arm was 0.26 kg (range –0.25 to
0.5 kg). Improvement in body condition score was seen in 5/9 cats in the
3.75 mg arm (P = 0.04) and 6/10 cats in the 1.88 mg arm (P = 0.004). Conclusions and relevance CTM increased appetite and resulted in weight gain in CKD cats despite
significant inconsistencies in compounding, and may benefit cats in
countries where an approved product is not available.
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Affiliation(s)
- Jessica M Quimby
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.,Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, OH, USA
| | - Kellyi K Benson
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Stacie C Summers
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | | | - Andrea K Herndon
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Shasha Bai
- Center for Biostatistics, The Ohio State University, Columbus, OH, USA
| | - Daniel L Gustafson
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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Poole M, Quimby JM, Hu T, Labelle D, Buhles W. A double-blind, placebo-controlled, randomized study to evaluate the weight gain drug, mirtazapine transdermal ointment, in cats with unintended weight loss. J Vet Pharmacol Ther 2018; 42:179-188. [PMID: 30506924 PMCID: PMC7379659 DOI: 10.1111/jvp.12738] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 11/02/2018] [Accepted: 11/05/2018] [Indexed: 01/09/2023]
Abstract
Mirtazapine is classified as a weight gain drug in cats, and the purpose of this study was to evaluate its efficacy in cats experiencing unintended weight loss. This was a multi-center, double-blind, placebo-controlled, randomized clinical study in client-owned cats ≥1 year of age, weighing ≥2 kg, with a documented loss (≥5%) in body weight. Cats were treated once daily with either 2 mg/cat mirtazapine transdermal ointment (n = 83) or placebo (n = 94) (Per Protocol population) applied to the inner surface of the pinna for 14 ± 3 days. Physical examination, body weight, complete blood count, serum chemistry, and urinalysis were performed prior to treatment and on Day 14. Changes in body weight between the mirtazapine and placebo groups were evaluated from Day 1 to Day 14 and compared using a two-sample t test. The mean percent change in body weight was +3.9% (standard deviation ±5.4%) in the mirtazapine group and +0.4% (±3.3%) in the placebo group (p < 0.0001). The most common adverse event was mild erythema at the application site in 17.4% of placebo and 10.4% of mirtazapine-treated cats. Application of mirtazapine transdermal ointment was well tolerated both topically and systemically and resulted in significant weight gain in cats experiencing unintended weight loss associated with various underlying diseases.
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Affiliation(s)
| | - Jessica M Quimby
- Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, Ohio
| | - Tianhua Hu
- Kindred Biosciences, Inc., Burlingame, California
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Buhles W, Quimby JM, Labelle D, Williams VS. Single and multiple dose pharmacokinetics of a novel mirtazapine transdermal ointment in cats. J Vet Pharmacol Ther 2018; 41:644-651. [PMID: 30004120 DOI: 10.1111/jvp.12691] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 04/04/2018] [Indexed: 11/29/2022]
Abstract
Single and multiple dose pharmacokinetics (PK) of mirtazapine transdermal ointment applied to the inner ear pinna of cats were assessed. Study 1 was a randomized, cross-over single dose study (n = 8). Cats were treated once with 0.5 mg/kg of mirtazapine transdermal ointment applied topically to the inner ear pinna (treatment) or administered orally (control) and then crossed over after washout. Plasma was collected predose and at specified intervals over 96 hr following dosing. Study 2 was a multiple dose study (n = 8). Cats were treated daily for 14 days with 0.5 mg/kg of mirtazapine transdermal ointment applied topically to the inner pinna. Plasma was collected on Day 13 predose and at specified intervals over 96 hr following the final dose. In Study 1, single transdermal administration of mirtazapine resulted in mean Tmax = 15.9 hr, Cmax = 21.5 ng/mL, AUC0-24 = 100 ng*hr/mL, AUC0-∞ = 260 ng*hr/mL and calculated half-life = 26.8 hr. Single oral administration of mirtazapine resulted in mean Tmax = 1.1 hr, Cmax = 83.1 ng/mL, AUC0-24 = 377 ng*hr/mL, AUC0-∞ = 434 ng*hr/mL and calculated half-life = 10.1 hr. Mean relative bioavailability (F) of transdermal to oral dosing was 64.9%. In Study 2, daily application of mirtazapine for 14 days resulted in mean Tmax = 2.1 hr, Cmax = 39.6 ng/mL, AUC0-24 = 400 ng*hr/mL, AUC0-∞ = 647 ng*hr/mL and calculated half-life = 20.7 hr. Single and repeat topical doses of a novel mirtazapine transdermal ointment achieve measurable plasma concentrations in cats.
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Affiliation(s)
| | - Jessica M Quimby
- Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, Ohio
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Benson KK, Zajic LB, Morgan PK, Brown SR, Hansen RJ, Lunghofer PJ, Wittenburg LA, Gustafson DL, Quimby JM. Drug exposure and clinical effect of transdermal mirtazapine in healthy young cats: a pilot study. J Feline Med Surg 2016; 19:998-1006. [PMID: 27613493 DOI: 10.1177/1098612x16667168] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
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.
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Affiliation(s)
- Kellyi K Benson
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Lara B Zajic
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Paula K Morgan
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Sarah R Brown
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Ryan J Hansen
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Paul J Lunghofer
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Luke A Wittenburg
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Daniel L Gustafson
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Jessica M Quimby
- Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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