Development and evaluation of a novel topically applied sildenafil citrate hydrogel and its influence on wound healing in dogs.

OBJECTIVE: To develop a topical sildenafil hydrogel and evaluate its effect on wound healing in dogs. ANIMALS: 6 purpose-bred, sexually intact, adult Beagles. PROCEDURES: Hydrogels containing sildenafil citrate, N-methyl-2-pyrrolidone, propylene glycol, and poloxamer 407 were developed. Four excision wounds were created along the dorsum of the dogs. Each wound was treated for 21 days with a nonadherent bandage (C) or with a hydrogel containing 0% (G), 5% (5S), or 10% (10S) sildenafil. Daily bandage changes with wound imaging were performed. Biopsy specimens were collected 5 times. RESULTS: Hydrogels were homogenous at room temperature and released > 90% of the sildenafil within 8 hours in vitro. Time to first granulation tissue was significantly shorter for the sildenafil groups (mean ± SD, 2.8 ± 0.8 days [5S and 10S]), compared with the control groups (5.2 ± 0.4 days [C] and 6.3 ± 1.4 days [G]). The G wounds had a 10% to 14% lower contraction rate, compared with the C, 5S, and 10S wounds. 5S wounds had a total wound area 0.7 ± 0.3 cm2 larger than 10S wounds. No significant differences were present when C wounds were compared with 5S and 10S wounds for total wound area, contraction, or epithelialization. Histologic acute inflammatory scores were higher for 5S and 10S wounds in the early and late stages of wound healing, with higher reparative scores on day 7. Neovascularization was higher for 10S wounds on day 7 and 14. CLINICAL RELEVANCE: The topical sildenafil hydrogel promoted early granulation tissue, which may be beneficial for secondary wound closure in clinical settings.

Clinical Feasibility and Airway Deposition of Nebulized Voriconazole in Healthy Horses.

Voriconazole (VRC) is a potential treatment for pneumomycosis in horses. The objectives of this study were to determine if the delivery of Vfend using a Flexineb nebulizer produced clinically significant [VRC] in lower airways. The hypothesis was that [VRC] after delivery by nebulization would be greater in the pulmonary epithelial lining fluid than plasma. A secondary objective was to determine [VRC] in upper airways through the collection of nasopharyngeal wash (NPW) samples. Voriconazole solution [Vfend-6.25 mg/mL, 100 (n = 2), 200 (n = 3), 500 (n = 1) mg] was nebulized once in 6 healthy geldings. Clinical responses, duration of nebulization, and [VRC] at various time points (up to 8 hours) in plasma, bronchoalveolar lavage fluid (BALF) supernatant and cell pellet, and NPW samples were recorded. Voriconazole (Vfend-6.25 mg/mL, 200 mg) was nebulized in 5 additional, healthy geldings, and [VRC] was measured in NPW samples pre- and postnebulization at time points up to 8 hours. The antifungal activity of BALF and NPW samples was determined using agar disk diffusion. Concentrations of voriconazole were below detection in plasma, BALF supernatant, and cell pellets for all time points and doses except the BALF cell pellet (0.4 µg/g) immediately after nebulization of 500 mg. For 5 horses, administered 200 mg of Vfend, mean [VCR] in NPW at the end of nebulization and 1, 6, and 8 hours postnebulization were: 30.8 ± 29, 1.0 ± 0.84, 0.2 ± 0.19, and 0.34 ± 0.67 µg/mL, respectively. Only NPW samples obtained immediately postnebulization showed antifungal activity. A nebulized Vfend solution is not recommended for the treatment of pneumomycosis in horses.

Pharmacokinetics of multivesicular liposomal encapsulated cytarabine when administered subcutaneously in dogs.

BACKGROUND: Prolonged cytotoxic concentrations of cytarabine (CA) are required for maximum cytotoxicity. DepoCyt is a human liposomal cytarabine (LC) product that lasts longer in plasma and CSF compared with free CA (FC). The use of LC has not been evaluated in dogs. OBJECTIVES: To perform a LC pharmacokinetic (PK) study when administered SC in dogs. ANIMALS: Five healthy female beagles. METHODS: Three-period, 3-treatment, nonblinded, randomized, and crossover design, including a pilot study. LC was administered at 50 mg/m2 SC and FC was administered at 25 and 50 mg/m2 SC and IV. Plasma CA concentrations were measured until 240, 72, and 8 hours after SC LC, SC FC, and IV FC administration, respectively. CA plasma concentrations were quantitated by ultra-high-performance liquid chromatography with mass spectrometry (MS/MS) detection and concentration-time profiles were evaluated by noncompartmental analysis. RESULTS: Subcutaneous LC administration resulted in a maximum plasma concentration of 26.3 to 59.78 ng/mL, time to reach maximum plasma concentration of 2 hours, area under the concentration-time curve to last measurable concentration of 669.3 to 1126 h × ng/mL, and plasma bioavailability (%F) of 19.6% to 31.3%. The PK profiles of FC after SC and IV administration differed when compared with LC. CONCLUSIONS AND CLINICAL IMPORTANCE: In healthy dogs, SC LC administration at 50 mg/m2 results in measurable plasma CA concentrations, is apparently safe and well tolerated, but does not result in prolonged cytotoxic plasma concentrations. Poor absorption of LC prevented establishment of a complete LC PK profile.

In Situ Gel Formulation for Enhanced Ocular Delivery of Nepafenac.

Nepafenac is a water-insoluble nonsteroidal antiinflammatory drug that is available as an ophthalmic suspension (Nevanac®). Suspensions are undesirable for 2 reasons: they tend to cause foreign body sensation and lacrimation, which could limit residence time and drug bioavailability. This decreases the amount of time the drug has to reach the site of action, the cornea. Previously, we improved the solubility and ocular permeability of nepafenac by complexing the drug with hydroxypropyl-ß-cyclodextrin. In this study, we used the complex to formulate an ion-activated in situ gel system using sodium alginate, Protanal PH 1033, to increase the residence time and to reduce repeat eye drop instillation. Rheological properties of the formulations revealed that the viscosity of the optimized formulation was increased 30-fold when exposed to the simulated tear fluid (35°C). Permeation studies showed that the drug concentration of the in situ formulations were approximately 10 times higher than the commercial product, Nevanac® (p < 0.001). In addition, the in situ gel formulations had 5-fold higher concentrations of nepafenac retained in the cornea when compared to Nevanac® (p <0.001). Finally, ex vivo drug distribution studies in the porcine eye perfusion model revealed a higher drug retention in various ocular tissues such as cornea, sclera, retina, as compared to Nevanac®.

A prospective, randomized, double-blind, placebo-controlled pilot study of sacubitril/valsartan (Entresto) in dogs with cardiomegaly secondary to myxomatous mitral valve disease.

BACKGROUND: The effects of sacubitril/valsartan (S/V) on the renin-angiotensin-aldosterone system (RAAS) in dogs with cardiomegaly secondary to myxomatous mitral valve disease (MMVD) are currently unknown. OBJECTIVES: To determine the pharmacodynamic effects of S/V on the RAAS, natriuretic peptide concentrations, systolic arterial pressure (SAP), tests of renal function, and serum electrolyte concentrations in dogs with cardiomegaly secondary to MMVD. ANIMALS: Thirteen client-owned dogs weighing 4-15 kg with American College of Veterinary Internal Medicine (ACVIM) Stage B2 MMVD. METHODS: Prospective, randomized, double-blind, placebo-controlled pilot study of S/V in dogs with ACVIM Stage B2 MMVD. RESULTS: Thirteen dogs were recruited: S/V (n = 7) and placebo (n = 6). The median percentage increase in urinary aldosterone to creatinine ratio (UAldo : C) between day 0 and day 30 was significantly lower in the S/V group (12%; P = .032) as compared with the placebo group (195%). The median percentage decrease of NT-proBNP concentration from day 0 to day 30 was not statistically different between groups (P = .68). No statistical differences were seen in echocardiographic, thoracic radiographic, SAP, or serum biochemical test results measured at any time point between groups. No adverse events were observed for dogs in either group. CONCLUSION AND CLINICAL IMPORTANCE: Sacubitril/valsartan may provide a new pharmaceutical method to effectively inhibit the RAAS in dogs with ACVIM Stage B2 MMVD.

Development of an automated plasmapheresis procedure for the harvest of equine plasma in accordance with current good manufacturing practice.

OBJECTIVE: To develop a high-speed, continuous-flow, automated plasmapheresis procedure for the high-volume harvest of equine plasma in accordance with current good manufacturing practice. ANIMALS: 143 horses (predominantly draft breeds) between 3 and 10 years of age at the time of purchase. PROCEDURES: Adaptations were made to automated plasmapheresis instruments and sterile disposable collection sets, which allowed for dual-instrument, continuous-flow operation. Donor horses were connected to the apparatus via 2 catheters (1 inserted in each jugular vein). The instruments removed whole blood from donors, fractionated the blood, diverted plasma to collection bags, and simultaneously returned concentrated cells to the donors. Plasmapheresis was performed on donor horses at 14-day intervals with a maximum of 22 mL of plasma/kg of donor body weight harvested during each plasmapheresis procedure. RESULTS: During a 5-year period, 3,240 plasmapheresis procedures were performed and > 50,000 L of sterile equine plasma was harvested in accordance with current good manufacturing practice. Donors typically remained calm during the plasmapheresis procedures and tolerated the procedures well. The high-volume and frequent plasma harvest did not result in sustained hypoproteinemia in donor horses. Adverse events associated with the automated plasmapheresis technique were infrequent, and the recurrence of adverse events was minimized by making minor adjustments to the procedure. CONCLUSIONS AND CLINICAL RELEVANCE: The automated plasmapheresis procedure described in this report can be used to safely harvest equine plasma or to perform therapeutic plasmapheresis in horses.

Effects of serial harvest of plasma on total plasma protein and total immunoglobulin G concentrations in donor horses involved in a plasmapheresis program.

OBJECTIVE: To determine the effects of intensive serial plasmapheresis on total plasma protein and total IgG concentrations in donor horses involved in a plasmapheresis program. ANIMALS: 18 horses (13 mares and 5 geldings; 13 Belgians, 3 Percherons, 1 Standardbred, and 1 warmblood) ranging from 7 to 14 years of age (mean ± SD, 10 ± 3 years) and weighing 822 ± 128 kg. PROCEDURES: Horses from which 22 mL of plasma/kg of donor body weight was harvested at 14-day intervals for a minimum of 8 consecutive plasmapheresis donations were retrospectively selected for use in the evaluation. Automated plasmapheresis procedures were performed by use of 2 modified plasmapheresis instruments/donor horse. Plasma samples were obtained at each donation and used for determination of total protein and total IgG concentrations. Total plasma protein concentrations were determined via refractometry. A commercially available ELISA was used to determine total equine IgG concentrations. RESULTS: The 18 donor horses were used in 8 to 19 serial donations (mean ± SD, 13 ± 3 donations) during the study. Donor horses had significant decreases in both plasma protein and IgG concentrations over the study period. CONCLUSIONS AND CLINICAL RELEVANCE: Serial plasmapheresis procedures caused significant decreases in both plasma protein and IgG concentrations in donor horses; however, decreases were not physiologically relevant. Performing plasmapheresis in horses in accordance with the evaluated automated plasmapheresis procedures did not result in a critical decrease in total plasma protein or total IgG concentrations.

Effects of intravenous administration of dimethyl sulfoxide on cardiopulmonary and clinicopathologic variables in awake or halothane-anesthetized horses.

OBJECTIVE: To evaluate the cardiopulmonary and clinicopathologic effects of rapid IV administration of dimethyl sulfoxide (DMSO) in awake and halothane-anesthetized horses. DESIGN: Prospective study. ANIMALS: 6 adult horses. PROCEDURES: Horses received IV infusion of 5 L of a balanced electrolyte solution with and without 1 g/kg (0.45 g/lb) of 10% DMSO solution when they were awake and anesthetized with halothane (4 treatments/horse). Arterial and venous blood samples were collected immediately before and at intervals during or after fluid administration and analyzed for blood gases and hematologic and serum biochemical variables, respectively. Heart rate, respiratory rate, and arterial blood pressure variables were recorded prior to, during, and after fluid administration. RESULTS: After administration of fluid with or without DMSO, changes in measured variables were detected immediately, but most variables returned to baseline values within 4 hours. One awake control horse had signs of anxiety; agitation and tachycardia were detected in 2 awake horses administered DMSO. These clinical signs disappeared when the rate of infusion was reduced. In anesthetized horses, increased concentrations of WBCs and plasma fibrinogen and serum creatine kinase activity persisted for 24 hours, which was related to the stress of anesthesia more than the effects of fluid administration. CONCLUSIONS AND CLINICAL RELEVANCE: Infusion of 5 L of balanced electrolyte solution with or without 10% DMSO induced minimal changes in cardiopulmonary function and clinicopathologic variables in either awake or halothane-anesthetized horses. Stress associated with anesthesia and recovery had a greater influence on measured variables in anesthetized horses than fluid administration.

Pharmacokinetics of subcutaneous selenium in adult llamas.

Selenium (Se) deficiency disease has been described in camelids and only clinical data is available for administration of parenteral Se supplements. This study investigated the pharmacokinetic effects of subcutaneous Se injection (0.1 mg/kg) in llamas fed a diet adequate in Se. Absorption of Se was rapid with peak whole blood Se concentration at the first sampling time. Significant differences in whole blood Se concentration from before injection of Se were not found past 2 days after Se injection. Parenteral Se is unlikely to have a long-term effect on whole blood Se concentration in llamas fed adequate dietary Se.

Pluronic F127 gel formulations of deslorelin and GnRH reduce drug degradation and sustain drug release and effect in cattle.

The objective of this study was to compare the effectiveness of intramuscular sustained release Pluronic F127 (PF127) gel formulations of deslorelin, a potent GnRH agonist, and GnRH to their solution formulations in inducing the release of luteinizing hormone and formation of luteal tissue in cattle. Injectable gel formulations of deslorelin and GnRH were prepared using Pluronic F127 (25%, w/w), a block copolymer. PF127 gels sustained the in vitro release of deslorelin as well as GnRH at similar rates and reduced drug degradation in muscle tissue when compared to the solution formulations. Deslorelin, as well as GnRH, elicited desirable elevations in plasma LH and progesterone concentrations in vivo. When compared to the solution formulations, the gel formulations of both drugs induced a broader peak of LH. Also, the peak LH levels were lower and the peak times were delayed with the gel formulations compared to the solution formulations. While the solution dosage form of deslorelin and GnRH elicited similar responses, the PF127 gel formulation of deslorelin induced peak LH levels at an earlier time (3 h for deslorelin versus 5.25 h for GnRH). The results indicate that, deslorelin exerts a pharmacological effect in cattle. The LH response to deslorelin as well as GnRH can be altered by controlling the input or the release rate of the drug. PF127 gel formulations can sustain peptide release and reduce peptide degradation.