The effects of equine skin preparation on transdermal drug penetration in vitro

An increasing number of formulations are applied to equine skin, yet variable penetration can affect efficacy, or the incidence of adverse effects, or both. To investigate the effects of common methods of skin preparation on transdermal drug penetration in vitro, we clipped, harvested, and froze skin samples from 5 Thoroughbred geldings. Thawed samples were prepared as follows: control (no preparation); cleaned with aqueous chlorhexidine (Aq-C, 0.1% w/v); cleaned with alcoholic chlorhexidine (Al-C, 0.5% w/v); shaved (Sh); or tape-stripped (Ta) with the use of adhesive tape. The samples were then placed in diffusion cells, and 2 g of methylsalicylate (MeSa) gel (Dencorub) was applied to the stratum corneum side. The penetration of MeSa and its analyte, salicylate (Sa), through the skin samples was measured over 10 h. Compared with control skin, significantly more MeSa penetrated through skin prepared with Al-C or Sh (P < 0.01) or with Aq-C or Ta (P < 0.05), and significantly more Sa was recovered in the receptor phase from skin prepared with Aq-C, Al-C, or Sh (P < 0.05) or with Ta (P < 0.01). A significantly higher rate of penetration and shorter lag time were also noted for MeSa with all the prepared skin samples, compared with the control samples. The results show that clinical techniques routinely used to clean or prepare skin can significantly affect the rate and extent of penetration of a topically applied drug. This may result in greater systemic availability of active drug, which could lead to enhanced efficacy and, possibly, a higher incidence of adverse effects.     

The effects of freezing skin on transdermal drug penetration kinetics

This study investigated the effects of freezing canine skin on the penetration kinetics of hydrocortisone. Skin samples from three dogs were used for in vitro penetration studies commencing on the day of skin collection (fresh skin) and again after freezing at -20 degrees C for 1, 4, 8 and 12 months. When the data from the dogs was averaged, the pseudo-steady-state flux (Jss) of hydrocortisone through skin frozen for any duration was significantly (P < 0.023) greater than through fresh skin and there was a positive relationship (P < 0.007) between the length of freezing and DeltaJss. For all dogs, the lag times (tlag) calculated for hydrocortisone penetration were significantly (P < 0.029) shorter through skin that had been frozen, compared with fresh skin. However, the shapes of the permeation profiles of hydrocortisone appeared similar through the fresh and frozen dog skins and no differences were detected between the groups on histological examination. The results of this study have shown that freezing dog skin at -20 degrees C can significantly increase the transdermal penetration of hydrocortisone in vitro, and that the extent of this enhancement can increase with duration of freezing.     

Regional differences in transdermal penetration of fentanyl through equine skin

The rate and regional differences for the penetration of fentanyl through equine skin was investigated in vitro using a commercial transdermal therapeutic system (TTS) or ‘patch’. Skin collected from the thorax, groin and leg (dorsal metacarpal) regions of five horses was placed in diffusion cells and a fentanyl TTS applied to each skin sample. Drug penetration through each skin sample over 48 h measured using high performance liquid chromatography (HPLC). Cumulative penetration (μg/cm²) was plotted against time (h) and used to regress the steady state flux (μg/cm²/h) of fentanyl through each skin site. Results showed similar fluxes for both the thorax (2.32 ± 0.17 μg/cm²/h and groin (2.21 ± 0.11 (μg/cm²/h) regions, but significantly lower flux (P = < 0.05) for the leg region (1.56 ± 0.120 μg/cm²/h. Interestingly, there was a significantly longer lag time for the penetration of fentanyl through the groin region (7.87 ± 0.51 h) compared to the other two sites (5.66 ± 0.97 h and 5.75 ± 0.43 h for the thorax and leg regions respectively). The results suggest that a fentanyl TTS applied to the leg region may have a small but significantly lower amount of fentanyl available systemically, compared to patches applied to the thorax or groin regions, which may affect the level of analgesia subsequently achieved in the horse.     

松萝酸体外透皮试验研究

采用简化体外透皮释放测定装置 ,初步研究了松萝酸在透皮促渗剂作用下的透皮吸收作用。结果表明单一的透皮促进剂氮酮 ( Azone)及以氮酮为主的复合透皮促进剂 ( 2 % Azone 2 0 %丙二醇 ,2 % Azone 2 0 %二甲基亚砜 ,2 % Azone 2 0 %尿素 )对松萝酸的透皮吸收均无促进作用     

Effects of transdermal lidocaine or lidocaine with prilocaine or tetracaine on mechanical superficial sensation and nociceptive thermal thresholds in horses

Objective

To evaluate the transdermal local anaesthetic effect of lidocaine or lidocaine combined with prilocaine or tetracaine in horses.

The effects of skin disease on the penetration kinetics of hydrocortisone through canine skin in vitro

This study investigated the effects of allergic skin disease on the penetration kinetics of hydrocortisone through canine skin in vitro. Full-thickness lesional and nonlesional (normal) skin was removed from the dorsal lumbosacral and dorsocaudal thoracic regions, respectively, of five canine cadavers. The dogs were suspected of having flea allergy dermatitis based on their distribution and types of skin lesions. Nonlesional skin was confirmed to be histologically normal, and the histopathology of the lesional skin was consistent with allergic dermatitis. Excised skin was clipped, mounted in Franz-type diffusion cells, and the transdermal penetration of a saturated, radiolabelled hydrocortisone solution was measured over 30 h. When the penetration data for all five dogs were pooled, a restricted (or residual) maximal likelihood mixed model predicted that the permeability coefficient and pseudosteady-state flux of hydrocortisone was more than twice as great (95% confidence interval 1.55-2.71 times as great; P < 0.0001) through lesional compared with nonlesional skin. There was no significant difference in the lag time for hydrocortisone penetration through lesional compared with nonlesional skin of the dogs. This study has confirmed that the transdermal penetration of hydrocortisone may be altered, typically increased twofold, but could be as high as 10-fold, through lesional compared with nonlesional skin of dogs with suspected flea allergy dermatitis. This is likely to be affected by variables such as disease severity, concurrent infections and interindividual differences in skin characteristics.     

Regional differences in the in vitro penetration of methylsalicylate through equine skin

Commercial formulations of non-steroidal anti-inflammatory drugs (NSAIDs) are developed for human use but the extent to which they will pass through equine skin is unknown. Skin was harvested from five Thoroughbred geldings from the thorax, groin and leg (dorsal metacarpal) regions and frozen (-20 degrees C) until required. Two grams of methylsalicylate (MeSa) gel was applied to defrosted full-thickness samples in diffusion cells and the penetration of MeSa and its active metabolite, salicylate (Sa), through skin samples were measured over 24 h. Significantly higher (P < or = 0.02) total salicylate (AUC; MeSa + Sa) penetrated through skin from the leg region (5491.3 h mg/L), compared to thorax (3710.7 h mg/L) and groin (3571.5 h mg/L). In addition, there was a significantly higher (P0.01) rate of penetration of total Sa through leg skin in the first 6h after application. It was concluded that the commercial formulation of MeSa would achieve therapeutic levels of total salicylate beneath sites of topical application, with a faster and more pronounced response through the leg region, compared to the upper body.     

Regional differences in the in vitro penetration of hydrocortisone through equine skin

Little is known about the transdermal penetration of hydrocortisone in the horse and, although commercial formulations containing hydrocortisone are registered for topical use in the horse, there have been no studies investigating the movement of this glucocorticoid through different regions of equine skin. Skin was harvested from the thorax, groin and leg (dorsal metacarpal) regions of five Thoroughbred geldings and frozen (-20 degrees C) until required. Defrosted skin was placed in Franz-type diffusion cells and the amount of radiolabelled ((3)H) hydrocortisone, in a saturated solution of unlabelled hydrocortisone in 50% ethanol (w/w), which penetrated through and remained within skin samples was measured over 24 h. Significantly higher (P < 0.001) maximum flux (J(max); mol/cm(2)/h) was measured when hydrocortisone was applied to skin from the leg, compared to thorax and groin, although significantly less hydrocortisone (P < 0.001) was retained within skin from the leg at 24 h. Topical application of hydrocortisone in a vehicle containing ethanol would penetrate faster through leg skin from the lower leg when compared with the thorax or groin, which depending on cutaneous blood flow, may result in higher systemic drug concentrations or greater efficiency in treating local inflamed tissue.     

薄荷醇和氮酮对甲硝唑在犬中体外透皮吸收的影响

研究不同的溶液载体（PBS,5％薄荷醇和5％氮酮）和不同部位的皮肤对甲硝唑在犬中体外透皮吸收和皮内摄取的影响。取下北京犬颈部、胸部以及腹部皮肤,-20℃保存。使用时,皮肤解冻固定在改良Franz透皮扩散仪上,保持恒速（200±1）r／min,恒温（35±0．5）℃。在扩散池中的皮肤角质层上加入2mL溶液载体（含甲硝唑58．4μmol）,以20％乙醇为溶剂溶解薄荷醇和氮酮,在预定时间点取样1mL,采用HPLC方法测定各接受液中的药物量和皮肤中摄取的药物量。结果显示,与PBS相比,薄荷醇和氮酮能增加所有部位甲硝唑的透皮吸收量和皮内摄取量（P〈0．05）。同一溶液载体在不同部位的渗透性存在差异,腹部〉颈部〉胸部,不同部位的皮内摄取量也存在差异,颈部〉胸部〉腹部。说明甲硝唑在不同溶液载体和不同部位皮肤的渗透性存在差异。     

The effects of vehicle and region of application on in vitro penetration of testosterone through canine skin

The effects of the vehicles phosphate-buffered saline (PBS), ethanol (EtOH; 50% in PBS w/w) and propylene glycol (PG; 50% in PBS w/w) and the region of administration on in vitro transdermal penetration of testosterone was investigated in the dog. Skin was harvested from the thorax, neck (dorsal part) and groin regions of greyhounds after euthanasia and stored at -20 degrees C until required. The skin was then de-frosted and placed into Franz-type diffusion cells which were maintained at approximately 32 degrees C by a water-bath. Saturated solutions of testosterone, containing trace amounts of radiolabelled (14C) testosterone, in each vehicle were applied to the outer (stratum corneum) surface of each skin sample and aliquots of receptor fluid were collected at 0, 2, 4, 8, 16, 20, 22 and 24h and analysed for testosterone by scintillation counting. The maximum flux (J(max)) of testosterone was significantly higher for all sites when dissolved in a vehicle containing 50% EtOH or 50% PG, compared to PBS. In contrast, higher residues of testosterone were found remaining within the skin when PBS was used as a vehicle. This study shows that variability in percutaneous penetration of testosterone could be expected with formulation design and site of application.     

果寡糖对生长绵羊瘤胃发酵功能(体外)的影响

采用批次培养的方法,研究了体外条件下日粮添加果寡糖对生长绵羊瘤胃发酵功能的影响。果寡糖的添加水平为0(对照组)、0.20%、0.40%、0.60%、0.80%及1.00%。结果表明,日粮添加果寡糖可以显著提高培养液中的挥发性脂肪酸(VFA)含量(P<0.05),当添加量在0.60%以上时,可以显著提高培养液中的微生物细菌蛋白质(BCP)含量(P<0.05),显著降低培养液中的NH3-N含量和培养残渣中的中性洗涤纤维(NDF)含量(P<0.05);在本试验所设添加范围内,1.0%的果寡糖对提高瘤胃发酵功能作用最优。研究初步证明,日粮添加果寡糖可以在一定程度上提高生长绵羊的瘤胃发酵功能。     

Intra-articular lidocaine plus bupivacaine in sheep undergoing stifle arthrotomy

Objective To evaluate the effect of intra‐articular (IA) lidocaine plus bupivacaine on post‐operative pain in sheep undergoing stifle arthrotomy. Study design Randomized controlled experimental trial. Animals Sixteen adult Rambouillet‐cross ewes. Methods Sheep were randomly assigned to one of two treatment groups. The lidocaine/bupivacaine group (L/B, n = 8) received IA lidocaine (40 mg (2 mL)) prior to incision and IA bupivacaine (10 mg (2 mL)) post‐closure, while the control group (n = 8) received no IA injections. IA local anesthetics were an addition to the standard analgesic protocol of phenylbutazone (1 g orally, every 24 hours for 5 days) and transdermal fentanyl (equivalent to 15 mg), initiated 24 hours prior to surgery. A stifle arthrotomy was performed with the purpose of creating a full‐thickness articular cartilage defect. Two observers blinded to treatment assessed sheep for total pain score using a numeric ranking scale that included: comfort, movement, and flock behavior. The first observation (T = 0) was obtained the evening of surgery (3–7 hours post‐operatively); subsequent observations occurred every 12 hours for 72 hours. Nonparametric statistical tests were used to evaluate differences between groups for total pain score. Results L/B sheep had significantly lower total pain scores at T = 0 than control sheep (p < 0.05). No significant differences between treatments were noted at any subsequent time periods. There were no differences attributable to the use of different observers. Conclusions and clinical relevance IA lidocaine plus bupivacaine provided analgesia at 3–7 hours post‐operatively. Use of IA lidocaine and bupivacaine is a simple, effective, yet inexpensive perioperative analgesic protocol for joint surgery in sheep.     

Comparison of lidocaine, lidocaine/epinephrine or bupivacaine for thoracolumbar paravertebral anaesthesia in fat-tailed sheep

ObjectiveTo evaluate the speed of onset and duration of loss of sensation in the flank following paravertebral administration of lidocaine (with or without epinephrine) or bupivacaine.Study designBlinded, randomized experimental study.AnimalsNine healthy fat-tailed male lambs (mean weight ± SD, 22.9 ± 3 kg). Each animal was used twice.MethodsAnimals were allocated randomly to receive two of three treatments: lidocaine 2% (LID, n = 6), lidocaine with epinephrine 5 μg mL^?1 (LIDEP, n = 6) or bupivacaine 0.5% (BUP, n = 6). The sheep received a total volume of 9 mL (3 mL for each paravertebral nerve) of anaesthetic. Onset and duration of loss of sensation on the flank were evaluated using nociceptive stimuli (superficial and deep pin-prick and clamping with a haemostat). Values for heart (HR) and respiratory (f_R) rates, rectal and skin temperatures were recorded before and at predetermined intervals after paravertebral injection. Parameters were compared using anova followed by Duncan’s test where relevant.ResultsMean ± SD times to onset of loss of flank sensation following paravertebral administration of LID, LIDEP or BUP were 1.8 ± 1.2, 2.0 ± 0.9 and 3.6 ± 1.3 minutes, respectively. Durations of action in minutes were 65 ± 18, 95 ± 46 and 303 ± 98, respectively. Onset and duration of effects after BUP treatment were significantly longer than after LID or LIDEP (p < 0.05), but did not differ significantly between LID and LIDEP. No clinical signs of local anaesthetic toxicity were noticed and HR and f_R remained stable with all protocols.Conclusions and clinical relevanceParavertebral administration of bupivacaine produces a longer duration of anaesthesia when compared to lidocaine with or without epinephrine and is indicated when prolonged flank surgery is to be performed.     

湖羊PGR基因对卵泡颗粒细胞体外增殖与凋亡的影响

旨在探究孕酮受体(progesterone receptor, PGR)基因对湖羊卵泡颗粒细胞体外增殖与凋亡的影响。利用RT-PCR技术扩增和克隆获得PGR基因编码序列(CDS),通过生物信息学软件对其氨基酸序列及同源性进行比对;用所获得序列构建过表达载体和干扰siRNA,分别转染湖羊颗粒细胞,并用CCK8技术检测颗粒细胞的细胞活力;采用RT-qPCR和Western blot技术,检测细胞周期和凋亡的相关基因或蛋白表达水平。结果显示,羊PGR基因的CDS区全长2 736 bp,编码911个氨基酸;与其他物种氨基酸序列的同源性为39.66%～95.44%。干扰PGR基因通过下调CDK4、Bcl-2和上调Caspas3、Caspase8、BAX基因mRNA的表达(P<0.05),进而抑制颗粒细胞的增殖,但对CyclinD1未产生影响(P>0.05);过表达PGR基因通过上调CDK4、CyclinD1、Bcl-2和下调Caspase3、Caspase8、BAX基因mRNA的表达(P<0.05),进而促进颗粒细胞的增殖;BAX蛋白表达变化与对应mRNA的表达趋势一致(P&l...     

Investigation of in vitro transdermal absorption of fentanyl from patches placed on skin samples obtained from various anatomic regions of dogs

OBJECTIVE: To investigate in vitro transdermal absorption of fentanyl from patches through skin samples obtained from various anatomic regions of dogs. SAMPLE POPULATION: Skin samples from 5 Greyhounds. PROCEDURE: Skin samples from the dogs' thoracic, neck, and groin regions were collected postmortem and frozen. After samples were thawed, circular sections were cut and placed in Franz-type diffusion cells in a water bath (32 degrees C). A commercial fentanyl patch, attached to an acetate strip with a circular hole, was applied to each skin sample. Cellulose strips were used as control membranes. Samples of receptor fluid in the diffusion cells were collected at intervals for 48 hours, and fentanyl concentrations were analyzed by use of high-performance liquid chromatography. RESULTS: Mean+/-SD release rate of fentanyl from the patch, defined by its absorption rate through the non-rate-limiting cellulose membrane, was linear during the first 8 hours (2.01+/-0.05 microg/cm2 of cellulose membrane/h) and then decreased. Fentanyl passed through skin from the groin region at a faster rate and with a significantly shorter lag time, compared with findings in neck or thoracic skin samples. CONCLUSIONS AND CLINICAL RELEVANCE: In vitro, fentanyl from a patch was absorbed more quickly and to a greater extent through skin collected from the groin region of dogs, compared with skin samples from the thoracic and neck regions. Placement of fentanyl patches in the groin region of dogs may decrease the lag time to achieve analgesia perioperatively; however, in vivo studies are necessary to confirm these findings.     

促渗剂促进药物透皮吸收机理的研究进展

综述了促渗剂促进药物透皮吸收机理的研究概况,着重介绍了氮酮、油酸和萜烯等常用促渗剂的促渗机理研究进展,并提出透皮吸收机理研究发展趋势,为该领域进一步深入研究提供参考.