Effect of vehicles on yohimbine permeation across excised hairless mouse skin

We aimed to provide a detailed analysis of substance P (SP)-containing nerves in the trabecular meshwork by ultrastructural immunohistochemistry and capsaicin treatment for chemical ablation of the sensory nerves. Numerous myelinated and unmyelinated nerves were observed inside the sheets and intertrabecular spaces of the trabecular meshwork, and the inner side of Schlemm's canal. SP-like immunoreactive products were identified in some of these nerves and associated with numerous vesicles of different sizes, a few mitochondria and numerous neurotubili. After the capsaicin treatment, SP-like immunoreactive nerves persisted and no degenerated SP-like immunoreactive nerves were noted. On the basis of the ultrastructural features and the results of capsaicin treatment, it seems that these nerves are most probably autonomic in origin. Autonomic efferent SP-containing nerves are confirmed directly located in the trabecular meshwork; these have not been previously described at electron microscopic level. SP in autonomic efferent nerves might act as a neurotransmitter or neuromodulator for intraocular pressure regulation.     

Enhancement effect of an ethanol/Panasate 800 binary vehicle on anti-inflammatory drug permeation across excised hairless mouse skin

A total of 65 adult cases (53 males, 12 females) with biopsy-proven focal segmental glomerulosclerosis (FSGS) were studied. Hypertension, ascites and haematuria were seen in 13, 12 and 24 cases, respectively. Decreased creatinine clearance at presentation was found in 9 cases. Mean proteinuria per day, serum cholesterol and total protein were 7.5 +/- 4.3 g, 388.95 +/- 213.4 mg% (10.11 +/- 5.55 mmol/l) and 5.27 +/- 1.1 g% (0.527 +/- 0.11 milligram), respectively. Mesangial proliferation was seen in 13 cases and hilar sclerosis in 5. Fifty percent showed positive immunofluorescence; IgM in 10, C3 in 8, and IgG in 2. Forty-two cases could be followed (mean 32 months), out of which 38 had nephrotic syndrome and were treated with prednisolone; 58% showed response (31% complete remission and 27% partial remission). One patient in each group of responders and nonresponders had renal failure at the end of follow-up. Hypertension, degree of proteinuria, mesangial proliferation, degree of tubular atrophy and immunofluorescence findings did not significantly affect the response to steroids. We conclude that a group of patients with idiopathic adult FSGS has a favourable response to steroids, which cannot be predicted clinically.     

Synthesis and effect of two new penetration enhancers on the transdermal delivery of 5-fluorouracil through excised rat skin

The tetrahydrogeraniol (THG) derivative, ethyl-(3,7-dimethyl octyl thio) acetate (EDOTA) was prepared by reacting tetrahydrogeranyl bromide (obtained by reaction of 40% hydrobromic acid and concentrated sulfuric acid) with ethyl 2-mercaptoacetate, while 3,7-dimethyl octyl propionate (DOP) was synthesized by a common esterification reaction by reacting THG with propionic acid in the presence of cyclohexane and concentrated sulfuric acid. The penetration-enhancing effect of the new enhancers were compared with THG and Azone in vitro using excised rat skin in modified Franz-type diffusion cells. 5-Fluorouracil (5-FU), a hydrophilic drug with poor skin permeability was used as a model permeant. Skin samples were pretreated with pure liquid enhancers for 12 h. 5-FU flux through the control and enhancer-treated skin increased linearly with its concentration in the receptor compartment. EDOTA and DOP interacted with the skin rapidly (< 2h), and the duration of action is at least 24 h. Significant differences were found in the flux values of 5-FU; EDOTA and DOP enhanced the permeability of the drug about 6-fold and 11-fold respectively. Increased partition coefficient and diffusion coefficient values were obtained by these enhancers. The results suggested that the amount of EDOTA and DOP in the skin, especially in the stratum corneum, may be related to their penetration-enhancing effect.     

In vitro percutaneous penetration through hairless rat skin: influence of temperature, vehicle and penetration enhancers

From February 1995 through October 1996, 25 patients with metastatic colorectal cancer showing a clinical resistance to 5-fluorouracil (5-FU) entered this study. Thirteen received oxaliplatin alone and 12 received it in combination with 5-FU. Oxaliplatin was administered at 130 mg/m2 over a 2-hour infusion every 3 weeks, alone or added either to 5-FU as a continuous infusion at 200 mg/m2 to 300 mg/m2 (six patients) or to a 5-FU bolus, 375 mg/m2, plus leucovorin, 100 mg/m2, daily for 5 days every 3 weeks (6 patients). Eighty-six of 98 administered cycles were evaluable for toxicity (47 for oxaliplatin plus 5-FU and 39 for oxaliplatin alone). Hematologic toxicity was mild, occurring as grade 2 leukopenia in 23% of the cycles of 5-FU and oxaliplatin and in 5% of the cycles of oxaliplatin alone. The most common toxicity was neurologic (grade 1 to 2 in 60%-6% of the cycles of the combination, respectively, and 68%-10% of oxaliplatin given alone) as hand-foot paresthesia or hypersensitivity to cold. No grade 4 toxicity was reported and only three patients in the 5-FU group developed grade 3 diarrhea. Grade 2 nausea and vomiting occurred in 33% of the cycles when both drugs were given and in 15% when oxaliplatin was administered alone. The combination of oxaliplatin and 5-FU induced four partial remissions (33%; 95% confidence interval, 6%-60%), whereas eight patients of the whole group had stable disease. No response occurred when oxaliplatin was administered as a single agent. The results of this study confirm the antitumor activity of oxaliplatin when added to 5-FU in patients who have metastatic colorectal cancer previously refractory to 5-FU. The possible therapeutic synergy with 5-FU was not accompanied by increased toxicity.     

Effect of electrodeposited metals on the permeation of hydrogen through iron membranes

The permeability of electrolytically charged hydrogen through annealed Ferrovac E iron membranes was found to decrease significantly upon coating the charging surface of iron with thin layers of either Pt, Cu or Ni (Watts or electroless). The absorption of hydrogen was delayed for a period which depends on the nature and the thicRness of the metallic coating. The results show that such coatings do not have to be thicR or even continuous to be effective, in which case a catalytic mechanism is proposed to explain the marRed reduction in hydrogen permeation through the iron. Experimental confirmation is presented of this catalytic mechanism and of the barrier mechanism which is operative in the presence of dense continuous coatings. It is also shown that a decrease in catalytic activity occurs with time (aging) and is pronounced in the presence of As³⁺ ion. Formerly Research Associate, The Pennsylvania State University     

In vitro study of the percutaneous absorption of four aromatic amines using hairless rat skin

Using hairless rat skin maintained in a Franz diffusion cell, the percutaneous penetration of four aromatic amines: para-chloroaniline (PCPA), meta-trifluoromethylaniline (mTFMA), dichloro-3,4-aniline (3,4-DCA) and dichloro-3,5-aniline (3,5-DCA) were studied. The purpose of the studies was to determine the permeation parameters (rate of permeation, permeability rat constant) in order to compare the rate of absorption of the four amines. The results show that the four amines penetrate significantly across the skin, but with different rates. 10 h after in vitro application (2 mg/cm2), the extent of permeation was PCPA > mTFMA > 3,4-DCA > 3,5-DCA.     

Testosterone skin permeation enhancement by menthol through formation of eutectic with drug and interaction with skin lipids

The aim of this investigation was to elucidate the mechanism of skin permeation enhancement of the lipophilic drug, testosterone, by menthol. Menthol was found to form eutectic mixtures with testosterone, cholesteryl oleate, and ceramides. DSC measurements showed that menthol drastically lowers the Tm of testosterone, from 153.7 to 39.9 degrees C. The decrease in Tm resulted in an increase in the solubility of testosterone in an aqueous ethanol vehicle by 2.8-fold, which caused a corresponding 2.8-fold increase in the flux of testosterone. A further increase in skin flux, to eight times the base line, could be attributed to the effect of menthol on the skin barrier properties. This assumption is supported by DSC results showing that menthol decreases the Tm of cholesteryl oleate and ceramides and modifies the thermogram profile of isolated stratum corneum. The results of this investigation indicate that menthol affects skin permeation by a dual mechanism: by forming a eutectic with the penetrating compound, thereby increasing its solubility, and by altering the barrier properties of the stratum corneum. Moreover, this study indicates that both types of interactions must be taken into consideration when using chemical enhancers and that decreasing the melting temperature of the permeant through formation of a eutectic could be one approach for increasing solubility and permeation rates.     

Effect of fractal dimension on drug permeation through porous ethylcellulose films

This paper describes a pilot investigation of first year nursing students' adherence to the recommended auscultatory blood pressure measurement procedure following three different forms of instruction; conventional classroom demonstration of the technique, a self instructional CD-ROM tutorial program, and a combination of both methods. This investigation was carried out over a 5-day time period using 27 students during normal teaching time. Students' adherence to the procedure was determined by observation using a performance checklist. Results suggest that the CD-ROM is no substitute for real life, hands on experience, although when used as an adjunct to traditional teaching methods, it can enhance learning.     

A 1H-NMR study of the permeation of glycolic acid through phospholipid membranes

The transmembrane permeability coefficient of the alpha-hydroxyacid, glycolic acid, has been measured for egg phosphatidylcholine large unilamellar vesicles. The determination of the vesicle concentration independent first-order rate constant for membrane transport and the permeability coefficient were made using an NMR technique employing shift agents. Both the temperature dependence and the dependence on cholesterol content were investigated. The activation energy and the Arrhenius pre-exponential factor were found to be dependent on the cholesterol content. A marked increase in both parameters was observed up to 20 mol% cholesterol, with a further, small increase up to 50%. The pH dependence of permeability was also investigated. An increase in permeability is observed with a decrease in pH, providing a possible explanation for the effectiveness of glycolic acid in skin treatment.     

Effect of carboxylic acids on permeation of chlorpromazine through dimethyl polysiloxane membrane

The effect of carboxylic acids on the permeation of chlorpromazine was investigated through a dimethyl polysiloxane nonpolar membrane. The permeability of the diffusate, at pH 5.8, increases considerably in the presence of carboxylic acids or phosphate, probably due to an ion-pair formation between the relative anions and chlorpromazine.     

Relationship between the skin permeation movement of propranolol and skin inflammatory reactions

We studied inflammatory reactions induced by dermal application of the beta-blocker propranolol (PRL) in ethanol to guinea pigs in order to elucidate the relation of the reactions with the cumulative PRL permeating amount through the stratum corneum or the PRL content in the stripped skin, and to investigate the chemical mediators responsible for the reactions. The cumulative PRL permeating amount through the stratum corneum increased rapidly up to 2 h after dermal application, then increased linearly with time up to 24 h after application. Visual observation revealed formation of erythema and edema at the applied site of PRL, and histopathological examination revealed infiltration of pseudoeosinophiles of dermis and epidermis and degeneration/necrosis of epidermis. In general, it was considered that the duration and the extent of these reactions were dependent on the PRL dosage and application time. It was expected that the cumulative PRL permeating amount through the stratum corneum could be used to predict possible inflammatory reactions during development of transdermal drug delivery systems. On the other hand, contact of PRL with guinea pig skin tissues released histamine, and intradermal injection of PRL caused an increase of capillary permeability at the site of application. Also, the inhibitory effects of anti-inflammatory agents (diphenhydramine, dexamethasone, indomethacin, cyproheptadine hydrochloride, CV3988 and AA-861) to PRL-induced erythema formation demonstrated that histamine and prostaglandins were responsible for the inflammatory reactions induced by PRL.     

Liposome-skin interactions and their effects on the skin permeation of drugs

The aim of the study was to evaluate the interaction of phospholipid liposomes with skin and stratum corneum lipid liposomes (SCLLs). The influence of phospholipid liposomes on the skin permeability of model drugs was also studied. The transdermal flux of the drugs applied in various phospholipid containing formulations through human epidermis was studied in diffusion chambers. Liposomes in water solutions did not enhance the skin permeability of the drugs, but when ethanol (32% w/v) was present in the donor with EPC (egg yolk lecithin), permeabilities of some model drugs were substantially increased. Confocal microscopy studies revealed that EPC do not penetrate into the skin from water solutions, while from ethanol solutions, EPC penetrates deeply into the stratum corneum. Also, resonance energy transfer between different liposome compositions and the release of calcein from SCLLs showed that interactions between phospholipid liposomes and SCLLs increased with increasing ethanol concentration in the liposome solutions.     

Effect of morphine and stadol on lipid content in liver of rat

The effects of repeated accumulative increasing doses (5, 10, 20 and 40 mg/kg body weight) of morphine and stadol on lipid content have been studied in liver of rat. The results obtained indicate that significant increases were recorded in hepatic triglycerides (TG) content after 1 and 12 hrs of morphine treatment while non-significant increases were recorded after stadol administration. After 36 hrs of treatment with either of the two drugs, the liver TG content was decreased which may indicate that drug tolerance might have developed. The phospholipids content showed increases especially after 12 hrs of morphine or stadol administration. The results obtained suggest enhanced phospholipid synthesis under the action of both drugs. Highly significant increases occurred in cholesterol content after 1, 12 and 24 hrs of treatment of both drugs. This might reflect the occurrence of decreased catabolism and turnover of cholesterol during the experiment. Total lipids content of liver showed marked and highly significant increases after 12 hrs of morphine and after 12 and 24 hrs of stadol administration respectively. The data obtained suggest that morphine and stadol may be hepatotoxic to rats.     

Effect of aging on the intestinal transport of hydrophilic drugs in the rat small intestine

The effect of aging on the intestinal transport of hydrophilic drugs (and probe compounds) was investigated in the rat small intestine. Passive transport was suggested to be unchanged with aging from 8 (young) to 54 (old) and further to 101 (very old) weeks old, as shown for D-xylose and urea in single-pass intestinal perfusion (under urethane anesthesia), where steady-state transport across the intestinal membrane into the blood stream was evaluated. The passive transports of cephradine, 5-fluorouracil (5-FU) and L-glucose were also unchanged, though they were compared only between the young and the old. Consistently, the passive uptake in the intestinal everted sacs, where the entry process into the membrane was evaluated for 5-FU, D-xylose, urea and polyethylene glycol (PEG) 900, was unchanged with aging from the young to the very old. The carrier-mediated transport of cephradine was also unchanged with aging from the young to the old in perfusion under anesthesia, though that of D-glucose was declined by about 50% with aging from the young to the old and thereafter remained constant in the very old. In perfusion in unanesthetized rats, age independency in passive transport (examined for cephradine, L-glucose and D-xylose) and an age-dependent decline in D-glucose transport were also observed, suggesting that the findings under anesthesia are not qualitatively distorted. These results suggest that, although carrier-mediated transport may moderately decline with aging, the barrier function of the intestinal membrane to passive permeation of hydrophilic drugs (with molecular weight below 1000) may be unaffected by aging, supporting the suggestion from our previous in vivo studies that age-dependent increases in the orally absorbed fraction may be predicted for incompletely absorbed drugs because of delayed intestinal transit rather than increased intestinal transport (membrane permeability).     

Cytokine induction in hairless mouse and rat skin after topical application of the immune response modifiers imiquimod and S-28463

ALDARA (imiquimod cream 5%) recently became available for the treatment of genital and perianal warts; however, the topical mechanism of action of imiquimod is not fully understood. Imiquimod, and its analogs R-842, S-27609, and S-28463, are potent anti-viral and anti-tumor agents in animal models. Much of the biologic activity of these compounds can be attributed to the induction of cytokines, including interferon-alpha, tumor necrosis factor-alpha, interleukins-1, -6, -8, and others. This study was performed to characterize the response of mice and rats to topical application of imiquimod and S-28463 and also to evaluate these agents in cultures of murine and human skin cells. Topical administration of imiquimod or S-28463 to the flanks of hairless mice and rats leads to increases in local concentrations of interferon and tumor necrosis factor in the skin. The concentrations of interferon and tumor necrosis factor were higher at the site of drug application than in skin from the contralateral flank or skin from untreated animals. Interferon-alpha mRNA levels were also elevated in the skin of mice after topical application of either imiquimod or S-28463. In vitro, both imiquimod and S-28463 induced increases in interferon and tumor necrosis factor in cultures of cells isolated from hairless mouse skin. Imiquimod also increased interleukin-8 concentrations in human keratinocyte and fibroblast cultures, whereas S-28463 induced increases in tumor necrosis factor in fibroblast cultures. These results demonstrate that imiquimod and S-28463 stimulate production of cytokines in the skin after topical application, which may play a major role in its activity in genital wart patients.     

Percutaneous penetration of 2-phenoxyethanol through rat and human skin

2-Phenoxyethanol applied in methanol was absorbed (64 +/- 4.4% at 24 hr) through unoccluded rat skin in vitro in the static diffusion cell with ethanol/water as receptor fluid. By comparison (43 +/- 3.7% in 24 hr) was absorbed in the flow-through diffusion system with tissue culture medium as receptor fluid. 2-Phenoxyethanol applied in methanol was absorbed (59.3 +/- 7.0% at 6 hr) through unoccluded human skin in vitro in the flow-through diffusion cell with tissue culture medium. With both unoccluded cells, 2-phenoxyethanol was lost by evaporation but occlusion of the static cell reduced evaporation and increased total absorption to 98.8 +/- 7.0%. Skin, post mitochondrial fraction, metabolized phenoxyethanol to phenoxyacetic acid at 5% of the rate for liver. Metabolism was inhibited by 1 mM pyrazole, suggesting involvement of alcohol dehydrogenase. However, first-pass metabolism of phenoxyethanol to phenoxyacetic acid was not detected during percutaneous penetration through viable rat skin in the flow-through system. First-pass metabolism in the skin does not therefore have an influence on systemic availability of dermally absorbed phenoxyethanol. These measures of phenoxyethanol absorption through rat and human skin in vitro agree well with those obtained previously in vivo.     

Effect of environmental conditions on the penetration of benzene through human skin

The in vitro penetration of [14C]benzene through freshly prepared human skin was examined under a variety of skin conditions associated with swimming and bathing. The experimental system utilized a recirculating donor solution and a flow-through receiver solution, and was modified to accommodate the analysis of volatiles. The permeability coefficient of 0.14 cm/h under standard conditions at 26 degrees C was found to increase to 0.26 cm/h at 50 degrees C and decrease to 0.10 cm/h at 15 degrees C. Storage of the skin at- 20 degrees C did not affect the penetration of benzene. Application of baby oil, moisturizer, or insect repellant to the skin before exposure under standard conditions did not affect the flux of benzene, but a significant increase was observed when the skin was pretreated with sunscreen (permeability coefficient 0.24 cm/h). These results suggest that risk assessment or exposure modeling for benzene and other environmental contaminants should account for appropriate changes in the environmental conditions when considering the dermal route of exposure.     

The effects of prolonged use of surfactants on the skin of normal and photo-exposed hairless mice

Cardiac surgery involves a complex of factors adversely affecting the pulmonary function (PF). Among them mainly pleurotomy and hypothermic phrenic nerve injury may potentially deteriorate postoperative PF. In a prospective study of 236 patients undergoing cardiac surgery, pre-, early and late postoperative PFs were evaluated. The impact of different techniques of coronary artery bypass grafting, of pleurotomy and diaphragmatic dysfunction and the effect of COPD on the postoperative modification of PF was investigated. The analysis revealed a substantial impairment of postoperative PF especially when pleural cavity was entered, the patients had COPD history, diaphragmatic dysfunction, or multiple pulmonary complications were present. These aspects should be considered in optimizing the pre-, per- and postoperative management of cardiac patients. (Tab. 5, Fig. 6, Ref. 34.)     

Cardiac microdialysis of salicylic acid .OH generation on nonenzymatic oxidation by norepinephrine in rat heart

The effect of pargyline, a monoamine oxidase inhibitor, on the generation of hydroxyl free radicals (.OH) was investigated using cardiac microdialysis. Salicylic acid in Ringer's solution (0.5 nmol x microL(-1) x min(-1)) was infused directly through a microdialysis probe to detect the generation of .OH as reflected by the formation of dihydroxybenzoic acid (DHBA) in the myocardium of anesthetized rats. When pargyline (100 nmol x microL(-1) x min(-1)) was infused in rat heart, the level of norepinephrine (NE) gradually increased in a time-dependent manner and an increase of DHBA was also observed. When NE was administered to the pargyline pretreated animals, a marked elevation in the levels of 2,3- and 2,5-DHBA formation was obtained, as compared to the group treated with NE only, showing a positive linear correlation between NE and .OH formation trapped as 2,3-DHBA (R2 = 0.981) or 2,5-DHBA (R2 = 0.984) in the dialysate. NE clearly produced an increase in .OH formation. These results indicate that accumulation of NE in the extracellular fluid elicited by pargyline can be auto-oxidized, which in turn, leads (possibly by an indirect mechanism) to the formation of cytotoxic .OH free radicals.