Biomedical subjects

Audra L Stinchcomb

Publications and source records attributed to Audra L Stinchcomb.

At least 19 recordsLinked to original sources

PubMed2006

Near infrared spectrometry for the quantification of human dermal absorption of econazole nitrate and estradiol.

PURPOSE: The purpose of this study was to demonstrate the use of near-infrared (NIR) spectrometry for the in vitro quantification of econazole nitrate (EN) and estradiol (EST) in human skin. METHODS: NIR spectra were collected from EN and EST powders to verify the presence of NIR chromophores. One percent EN cream, a saturated solution of EN, or 0.25% EST solution was applied to human skin. NIR spectra were collected and one-point net analyte signal (NAS) multivariate calibration was used to predict the drug concentrations. NIR results were validated against known skin concentrations measured by high-pressure liquid chromatography (HPLC) analysis of solvent extracts. RESULTS: NIR spectroscopy measured dermal absorption from saturated solutions of EN on human skin with an r2=0.990, standard error of estimation (SEE)=2.46%, and a standard error of performance (SEP)=3.55%, EN cream on skin with an r2=0.987, SEE=2.30%, and SEP=2.66%, and 0.25% solutions of EST on skin with an r2=0.987, SEE=3.30%, and SEP=5.66%. Despite low permeation amounts of both drugs through the stratum corneum into human tissue, the NIR signal-to-noise ratio was greater than three, even for the lowest concentrations. CONCLUSION: NIR analyses paralleled the results obtained from HPLC, and thus could serve as a viable alternative for measuring the topical bioavailability/bioequivalence of different EN and EST formulations. Because these experiments were conducted in human tissue, this research suggests an all-optical in vivo method of measurement for dermal absorption could be developed.

Administration, Topical↗

PubMed2006

Inhibition of calpain-mediated cell death by a novel peptide inhibitor.

Calpains are calcium- and thiol-dependent proteases whose overactivation and degradation of various substrates have been implicated in a number of diseases and conditions such as cardiovascular dysfunction and ischemic stroke. With increasing evidence for calpain's role in cellular damage, the development of calpain inhibitors continues to be an important objective. Previously, we identified a highly specific calcium-dependent, calpain interacting peptide L-S-E-A-L, that showed homology to domains A and C of the only known endogenous inhibitor of calpains, calpastatin. This suggested that LSEAL had a calpain inhibitory function and synthetic LSEAL inhibited calpain I and II proteolysis of two calpain substrates, tau and alpha-synuclein. In the present study, we demonstrate that synthetic LSEAL is membrane permeable and is a potent inhibitor in two established models of calpain-mediated cell death using primary rat cortical neurons and SH-SY5Y neuroblastoma cells. In addition, we show that LSEAL inhibits calpain activity towards protein substrates as detected by an antibody to a calpain-specific breakdown product of spectrin. Taken together, these results suggest that LSEAL may represent a novel calpastatin mimetic with the potential for benefit in conditions of increased calpain activity such as stroke, traumatic brain injury or heart attack.

Adenosine Triphosphate↗

PubMed2006

Intranasal absorption of Delta(9)-tetrahydrocannabinol and WIN55,212-2 mesylate in rats.

The aim of this study was to examine the potential of the nasal route for systemic delivery of Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and WIN55,212-2 mesylate. Anesthetized rats were surgically prepared to isolate the nasal cavity, into which Delta(9)-THC (10 mg/kg) or WIN55,212-2 (150 microg/kg) in propylene glycol alone or propylene glycol and ethanol (9:1) were administered. Rats were also administered Delta(9)-THC (1 mg/kg) and WIN55,212-2 (150 microg/kg) intravenously in order to determine absolute bioavailabilities of the nasal doses. Plasma Delta(9)-THC and WIN55,212-2 concentrations were determined by liquid chromatography/mass spectroscopy (LC/MS). The pharmacokinetics of the drugs after intranasal administration was best described by a one-compartment model with an absorption phase. WIN55,212-2 was absorbed more rapidly (T(max)=0.2-0.3h) than Delta(9)-THC (T(max)=1.5-1.6h) and to a higher extent than Delta(9)-THC. Addition of ethanol (10%) to the formulations had no significant effect on the C(max) after nasal administration (p>0.05). Furthermore, it had no significant effect on the absolute bioavailability (F(abs)): F(abs)=6.4+/-2.4% and 9.1+/-3.0% for Delta(9)-THC in propylene glycol, with and without ethanol, respectively. For WIN55,212-2, F(abs)=49.9+/-6.9% (propylene glycol alone) and 56.6+/-14.1% (propylene glycol with 10% ethanol). The results of the study showed that systemic delivery of Delta(9)-tetrahydrocannabinol and WIN55,212-2 could be achieved following nasal administration in rats.

Absorption↗

PubMed2006

Synthesis and hydrolytic behavior of two novel tripartate codrugs of naltrexone and 6beta-naltrexol with hydroxybupropion as potential alcohol abuse and smoking cessation agents.

A codrug approach for simultaneous treatment of alcohol abuse and tobacco dependence is considered as very desirable because of substantial evidence that smoking is increased significantly during drinking, and that smoking is regarded as a behavioral 'cue' for the urge to consume alcohol. The purpose of this study was to design and synthesize codrugs for simultaneous treatment of alcohol abuse and tobacco dependence. Two novel tripartate codrugs of naltrexone (NTX) and naltrexol (NTXOL) covalently linked to hydroxybupropion (BUPOH) were synthesized (25 and 26, respectively), and their hydrolytic cleavage to the parent drugs was determined. These codrugs were generally less crystalline when compared to NTX, or NTXOL, as indicated by their lower melting points, and were expected to be more lipid-soluble. Also, the calculated clogP values were found to be higher for the codrugs compared to those for NTX and NTXOL. The studies on the hydrolysis of the codrugs provided good evidence that they could be efficiently converted to the parent drugs in buffer at physiological pH. Thus, these codrugs are likely to be cleaved enzymatically in vivo to generate the parent drugs, and are considered to be potential candidates for simultaneous treatment of alcohol abuse and tobacco dependence.

Alcohol Deterrents↗

PubMed2006

Enhancement of transdermal delivery of 6-beta-naltrexol via a codrug linked to hydroxybupropion.

Naltrexone (NTX) is a potent opioid antagonist used in the treatment of alcohol dependence and heroin abuse. Compared with naloxone, NTX has a longer duration of action largely attributed to its major active metabolite, 6-beta-naltrexol. The purpose of this study was to increase the delivery of 6-beta-naltrexol across human skin in vitro via a novel codrug. A carbonate codrug of 6-beta-naltrexol linked to hydroxybupropion was synthesized and evaluated. In vitro human skin permeation rates were measured using a flow-through diffusion cell system. The drug melting points, solubilities, chemical stability, and skin disposition were determined. The carbonate codrug was hydrolyzed on passing through skin and appeared as a combination of intact codrug and parent drugs, 6-beta-naltrexol and hydroxybupropion, in the receiver solution. The codrug provided a significantly (p<0.05) higher 6-beta-naltrexol flux across human skin than 6-beta-naltrexol base. The extent of parent drug regeneration in the skin ranged from 56 to 86%. A higher stratum corneum partition coefficient and rapid bioconversion of the carbonate codrug in the skin correlated with increased 6-beta-naltrexol delivery rates.

Administration, Cutaneous↗

PubMed2006

Near-infrared spectrometry for the quantification of dermal absorption of econazole nitrate and 4-cyanophenol.

PURPOSE: The purpose of this study was to demonstrate the utility of near-infrared (NIR) spectroscopy for the in vitro quantification of econazole nitrate (EN) and 4-cyanophenol (4-CP) in hairless guinea pig skin. METHODS: NIR spectra were collected from each of the following: EN and 4-CP powders, EN and 4-CP in solution, and skin samples following topical exposure to either 4-CP in water or EN in propylene glycol and topical creams. To predict drug concentration from NIR spectra, principal component regression (PCR), interval PCR, and uninformative variable elimination PCR were each used with a leave-one-out cross-validation, and results were compared. NIR results were validated against known skin concentrations measured by high-pressure liquid chromatography (HPLC) analysis of solvent extracts. RESULTS: NIR results matched the HPLC results for the quantification of 4-CP and EN in skin exposed to saturated solutions and topical creams with an r2 > 0.90, a standard error of estimation < 7.0%, and a standard error of performance < 8.0%. CONCLUSION: This experiment demonstrated that NIR closely parallels results obtained from tissue extraction and HPLC analysis, proving its potential utility for the rapid and noninvasive determination of topical bioavailability/bioequivalence of EN and quantification of the model chemical 4-CP. Investigation of drugs in human skin is now justified.

Algorithms↗

PubMed2006

Permeation of WIN 55,212-2, a potent cannabinoid receptor agonist, across human tracheo-bronchial tissue in vitro and rat nasal epithelium in vivo.

The aim of this study was to investigate the intranasal absorption of R-(+)-WIN 55,212-2 mesylate in vivo and in vitro. Permeation experiments of R-(+)-WIN 55,212-2 formulations with 2% dimethyl-beta-cyclodextrin (DMbetaCD), 2% trimethyl-beta-cyclodextrin (TMbetaCD) or 2% randomly methylated-beta-cyclodextrin (RAMbetaCD) in 1:1 propylene glycol/saline and 1.5% propylene glycol +3% Tween 80 in saline were conducted using EpiAirway tissue and an anesthetized rat nasal absorption model, respectively. Samples were analysed by liquid chromatography-mass spectrometry. Mucosal tolerance was screened using paracellular marker permeation and tissue viability as indices. Nasal absorption of WIN 55,212-2 was rapid, with a t(max) (time of peak concentration) of 0.17 to 0.35 h in vivo. Relative to 1.5% propylene glycol +3% Tween 80 (control), 1:1 propylene glycol/saline, RAMbetaCD, DMbetaCD and TMbetaCD resulted in 24-, 20-, 17- and 10-fold WIN 55,212-2 permeation increases in vitro, respectively. The in vivo absolute bioavailabilities were also increased with 1:1 propylene glycol/saline, RAMbetaCD, DMbetaCD and TMbetaCD compared to 1.5% propylene glycol +3% Tween 80 (0.15 vs. 0.66-0.77). The viability of the EpiAirway tissues was significantly reduced by DMbetaCD and TMbetaCD formulations. This study showed that WIN 55,212-2 mesylate can be delivered via the nasal route. Absorption of R-(+)-WIN 55,212-2 was rapid and bioavailability was significantly improved using methylated cyclodextrins and propylene glycol-based cosolvent.

Administration, Intranasal↗

PubMed2005

In vitro/in vivo correlation of transdermal naltrexone prodrugs in hairless guinea pigs.

PURPOSE: The purpose of this investigation was to evaluate the in vitro and in vivo percutaneous absorption of the following prodrugs of naltrexone (NTX): 2'-ethylbutyryl-3-O-ester-NTX (ETBUT-ester), methyl-3-O-carbonate-NTX (ME-carbonate), ethyl-3-O-carbamate-NTX (ET-carbamate), and N,N-dimethyl-3-O-carbamate-NTX (DME-carbamate) in hairless guinea pigs. METHODS: In vitro fluxes of NTX and its prodrugs through guinea pig skin were determined using a flow-through diffusion cell system. The pharmacokinetics of NTX prodrugs were determined after topical application of transdermal patches in guinea pigs. RESULTS: All the prodrugs hydrolyzed to NTX on passing through the skin, and ME-carbonate provided the highest NTX flux and had the highest apparent permeability coefficient (K(p)). ME-carbonate and ET-carbamate underwent the highest extent of bioconversion to NTX upon passing through the skin as compared to ETBUT-ester and DME-carbamate. The results of the in vivo studies indicated that a significant amount of NTX was delivered after the application of transdermal patches of NTX prodrugs. A mean steady-state plasma concentration of 7.1 ng/ml was obtained after the application of transdermal patches of ME-carbonate. A good correlation was obtained between the in vitro and in vivo results. CONCLUSIONS: The results of the in vivo studies indicated that the ME-carbonate prodrug of NTX was the most promising drug candidate for transdermal delivery.

Administration, Cutaneous↗

PubMed2005

Human skin permeation of branched-chain 3-0-alkyl ester and carbonate prodrugs of naltrexone.

PURPOSE: Physicochemical characterization and in vitro human skin diffusion studies of branched-chain ester and carbonate prodrugs of naltrexone (NTX) were compared and contrasted with straight-chain ester and carbonate NTX prodrugs. METHODS: Human skin permeation rates, thermal parameters, solubilities in mineral oil and buffer, and stabilities in buffer and plasma were determined. Partition coefficients between stratum corneum and vehicle were determined for straight- and branched-chain esters with the same number of carbon atoms. RESULTS: Branched prodrugs had lower melting points, lower buffer solubilities, and higher mineral oil solubilities than NTX. The transdermal flux values from all of these branched prodrugs were significantly lower than flux values from the straight-chain ester and the methyl carbonate prodrugs. Straight-chain prodrugs had higher partition coefficient values and higher calculated thermodynamic activities than their branched-chain counterparts. The prodrug hydrolysis to NTX in buffer and plasma was slower for prodrugs with increased branching. CONCLUSIONS: Branched-chain prodrugs with bulky moieties had smaller stratum corneum-vehicle partition coefficients and lower thermodynamic activities that resulted in smaller transdermal flux values than straight-chain prodrugs.

Abdomen↗

PubMed2005

In vivo evaluation of 3-O-alkyl ester transdermal prodrugs of naltrexone in hairless guinea pigs.

Naltrexone (NTX) is a potent competitive antagonist with high affinity for the mu-opioid receptor. Therapeutically, NTX is used for the treatment of alcohol dependence and opioid addiction; however, it does not have the ideal physicochemical properties necessary to achieve therapeutic plasma concentrations via the transdermal route. The aim of the present investigation was to evaluate the in vivo transdermal delivery of three 3-O-alkyl ester prodrugs of NTX, including NTX-3-O-acetate (ACE-NTX), NTX-3-O-propionate (PROP-NTX), and NTX-3-O-hexanoate (HEX-NTX) in hairless guinea pigs. The pharmacokinetic parameters for NTX and the 3-O-alkyl ester prodrugs of NTX were determined after intravenous drug administration and topical drug application of transdermal therapeutic systems (TTS) in guinea pigs. The results of the in vivo studies showed mean steady-state plasma concentrations of NTX from NTX, ACE-NTX, PROP-NTX and HEX-NTX at 4.2, 25.2, 16.0, and 8.3 ng/mL, respectively. These NTX plasma concentrations were maintained for 48 h. The results of these in vivo studies demonstrated that ACE-NTX and PROP-NTX prodrugs of NTX were the most promising drug candidates for transdermal delivery.

Acetates↗

PubMed2005

LC-MS method for the estimation of delta8-THC and 11-nor-delta8-THC-9-COOH in plasma.

The aim of the present study was to develop a simple and sensitive LC-MS method for the estimation of delta8-tetrahydrocannabinol (delta8-THC) and its metabolite, 11-nor-delta8-tetrahydrocannabinol-9-carboxylic acid (11-nor-delta8-THC-9-COOH), in guinea pig plasma after topical drug application. The plasma samples were analyzed by LC-MS using negative-mode electrospray ionization detection and a simple liquid-liquid extraction technique. The mean recoveries for delta8-THC and its metabolite, 11-nor-delta8-THC-9-COOH, were 96.6 and 88.2%, respectively. The lower limits of quantification (LLOQ) for delta8-THC and 11-nor-delta8-THC-9-COOH were 3.97 and 7.26 nM, respectively. The topical treatment steady-state plasma concentrations of delta8-THC and 11-nor-delta8-THC-9-COOH were 8.24-27.63 and 19.66-23.17 nM, respectively, with a lag period of 0.3-2.2 h. This assay method is selective, sensitive, and reproducible for the determination of delta8-THC and 11-nor-delta8-THC-9-COOH at low concentrations in small volumes of plasma.

Animals↗

PubMed2005

Bioconversion of naltrexone and its 3-O-alkyl-ester prodrugs in a human skin equivalent.

The purpose of this study was to compare the percutaneous absorption and bioconversion of naltrexone (NTX), naltrexone-3-O-valerate (VAL), and naltrexone-3-O-(2'-ethylbutyrate) (ETBUT) in a human skin equivalent model (EpiDerm) and in fresh human skin in vitro. NTX diffusion and metabolism to 6-beta-naltrexol (NTXol) were quantitated and compared in the EpiDerm and in excised fresh human skin. VAL and ETBUT diffusion and bioconversion studies were also completed in EpiDerm. Naltrexone bioconverted to levels of 3+/-2% NTXol in the EpiDerm and 1+/-0.5% in fresh human skin. VAL hydrolyzed rapidly in the EpiDerm and mainly (93+/-4%) NTX was found in the receiver compartment, similar to human skin. More intact ETBUT permeated the EpiDerm tissue compared to VAL, and only 15+/-11% NTX was found in the receiver. Significantly higher fluxes of NTX and the prodrugs were observed with the EpiDerm compared to human skin. A similar flux enhancement level was observed for VAL, compared to NTX base, in the EpiDerm and the human skin. Metabolically active human epidermal models like EpiDerm are useful as an alternative experimental system to human skin for prediction of topical/transdermal drug/prodrug bioconversion.

Algorithms↗

PubMed2005

Transdermal delivery of naltrexone and its active metabolite 6-beta-naltrexol in human skin in vitro and guinea pigs in vivo.

The aim of the present study was to evaluate the transdermal delivery of 6-beta-naltrexol (NTXOL), the active metabolite of naltrexone (NTX), across human skin and guinea pig skin in vitro and in hairless guinea pigs in vivo. NTXOL may be responsible for much of NTX's pharmacologic activity. In vitro diffusion studies on NTXOL were compared with similar studies on NTX using a formulation of propylene glycol and buffer in a flow-through diffusion cell system. In vivo guinea pig studies were carried out involving topical application of both drugs in patches containing identical formulations. The in vitro flux of NTX was about 2.3- and 5.6-fold higher than for NTXOL across guinea pig skin and human skin, respectively. NTXOL lag times were longer than NTX in both skin types. In vivo studies in guinea pigs showed that the steady-state plasma level of NTX was twofold greater than NTXOL, which correlated well with in vitro data. The results of the present study indicated that substantial levels of NTX and NTXOL could be delivered via the transdermal route, although the plasma levels of NTXOL were significantly less than NTX. Further transdermal formulation development will be investigated for permeation enhancement.

Administration, Cutaneous↗

PubMed2005

In vitro release studies on matrix type transdermal drug delivery systems of naltrexone and its acetyl prodrug.

Matrix type acrylic adhesive transdermal patches of naltrexone (NTX) and its 3-O-acetyl ester prodrug were prepared and evaluated for drug content, thickness, and in vitro release characteristics. Among the four DURO-TAK adhesive polymers (87-2516, 87-2054, 87-2501, and 87-2582) tested, 87-2516 proved to be the most suitable and compatible polymer for the transdermal delivery of NTX from NTX and prodrug patches. A linear relationship was observed for release flux (F) and cumulative amount (Mt) values versus 1%, 2%, and 3% drug loading at equimolar levels. The release of NTX from the patches showed a good correlation (R2>0.99) for Mt vs. square root t profiles, indicating that a Higuchian matrix diffusion mechanism of drug release from the transdermal adhesive patches was obtained. Overall, the amounts of NTX released from the prodrug patches were significantly higher than from the NTX patches, at all three drug loading levels.

Acetylation↗

PubMed2004

Development and validation of a liquid chromatography-mass spectrometry method for the quantitation of naltrexone and 6beta-naltrexol in guinea pig plasma.

A quantitative liquid chromatographic-electrospray ionization mass spectrometry method for the determination of naltrexone and 6beta-naltrexol in guinea pig plasma has been developed and validated using naloxone as an internal standard. A single step precipitation-extraction technique was carried out to extract the plasma samples using acetonitrile:ethyl acetate (1:1, v/v). The chromatographic separation was performed on a C(18) column using a mobile phase consisting of 35:65 (v/v) acetonitrile:2 mM ammonium acetate with 0.01 mM ammonium citrate at a flow rate of 0.25 mL/min. The analyte was detected after positive electrospray ionization using selected ion monitoring (SIM) mode. The mean recoveries for naltrexone, naltrexol, and naloxone were 91.7, 89.3, and 99.0%, respectively. The lower limit of quantification (LLOQ) for naltrexone and 6beta-naltrexol was 1.25 ng/mL, and the limit of detection (LOD) was 0.75 ng/mL. The method was applied to a pharmacokinetic study in order to assess the drug disposition of naltrexone in guinea pigs.

Animals↗

PubMed2004

Transdermal permeation of WIN 55,212-2 and CP 55,940 in human skin in vitro.

Synthetic cannabinoids have a promising future as treatments for nausea, appetite modulation, pain, and many neurological disorders. Transdermal delivery is a convenient and desirable dosage form for these drugs and health conditions. The aim of the present study was to investigate the in vitro transdermal permeation of two synthetic cannabinoids, WIN 55,212-2 and CP 55,940. Transdermal flux, drug content in the skin, and lag times were measured in split-thickness human abdominal skin in flow-through diffusion cells with receiver solutions of 4% bovine serum albumin (BSA) or 0.5% Brij 98. Differential thermal analysis (DSC) was performed in order to determine heats of fusion, melting points, and relative thermodynamic activities. The in vitro diffusion studies in 0.5% Brij 98 indicated that WIN 55,212-2 diffuses across human skin faster than CP 55,940. The WIN 55,212-2 skin disposition concentration levels were also significantly higher than that of CP 55,940. Correspondingly, CP 55,940 was significantly metabolized in the skin. WIN 55,212-2 flux and skin disposition were significantly lower into 4% BSA than into 0.5% Brij 98 receiver solutions. There was no significant difference in the flux, lag time, and drug content in the skin of CP 55,940 in 4% BSA versus 0.5% Brij 98 receiver solutions. The DSC studies showed that CP 55,940 had a significantly lower melting point, smaller heat of fusion, and corresponding higher calculated thermodynamic activity than the more crystalline WIN 55,212-2 mesylate salt. The permeation results indicated that WIN 55,212-2 mesylate, CP 55,940, and other potent synthetic cannabinoids with these physicochemical properties could be ideal candidates for the development of a transdermal therapeutic system.

Administration, Cutaneous↗

PubMed2004

A duplex "Gemini" prodrug of naltrexone for transdermal delivery.

Transdermal naltrexone delivery is desirable in the treatment of narcotic dependence and alcoholism. The purpose of this study was to increase the delivery rate of naltrexone (NTX) across human skin by using a novel prodrug. A duplex "gemini" prodrug of naltrexone was synthesized and evaluated. In vitro human skin permeation rates of naltrexone and prodrug were measured using a flow-through diffusion cell system. Drug concentrations in the skin were quantitated at the end of the diffusion experiment. The prodrug was hydrolyzed on passing through the skin and appeared mainly as naltrexone in the receiver compartment. The prodrug provided a significantly higher naltrexone equivalent flux across human skin in vitro than naltrexone base. The naltrexone equivalent solubilities of naltrexone and the prodrug in the donor solution were not significantly different. No significant increase in drug concentration in the skin after prodrug treatment, as compared to naltrexone, was observed. The naltrexone equivalent permeability from the prodrug exceeded the permeability of naltrexone base by two-fold. Due to the design of this prodrug, toxicities associated with this compound should be nonexistent, because only naltrexone and carbon dioxide (carbonic acid) are released when the prodrug is cleaved.

Administration, Cutaneous↗

PubMed2004

Liquid chromatographic-mass spectrometric quantitation of Delta9-tetrahydrocannabinol and two metabolites in pharmacokinetic study plasma samples.

A sensitive method for the determination of Delta(9)-tetrahydrocannabinol and its metabolites, 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid and 11-hydroxy-Delta(9)-tetrahydrocannabinol, in rat and guinea pig plasma was developed using high-performance liquid chromatographic separation with electrospray ionization mass spectrometry detection and a simple liquid-liquid extraction technique. The mean recoveries for Delta(9)-tetrahydrocannabinol, 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid, and 11-hydroxy-Delta(9)-tetrahydrocannabinol were 96, 92, and 85%, respectively. The lower limit of quantification (LLOQ) for all three compounds was 5 ng/ml and the limit of detection (LOD) was 2 ng/ml. This assay method utilizes the increased sensitivity and selectivity of mass spectrometric (MS) detection and a simple extraction step for the determination of Delta(9)-tetrahydrocannabinol and its metabolites in plasma, and thus yields a more efficient pharmacokinetic analysis method than has previously been described.

Animals↗