Enhanced bioavailability of danazol nanosuspensions by wet milling and high-pressure homogenization.

INTRODUCTION: The majority of drugs obtained through synthesis and development show poor aqueous solubility and dissolution velocity, resulting in reduced bioavailability of drugs. Most of these problems arise from formulation-related performance issues, and an efficient way to overcome these obstacles and to increase dissolution velocity is to reduce the particle size of drug substances to form drug nanosuspensions. MATERIALS AND METHODS: Danazol nanosuspensions were prepared by wet milling (WM) and high-pressure homogenization (HPH) methods. The nanosuspensions obtained using these fabrication methods were analyzed for their particle size, surface charge, and the crystallinity of the product was assessed by X-ray diffraction (XRD) and differential scanning calorimetry techniques. To determine in vitro and in vivo performances of the prepared nanosuspensions, dissolution velocity, and bioavailability studies were performed. RESULTS: Particle size and zeta potential analysis showed the formation of nanosized particles with a negative charge on the surface. XRD depicted the nanocrystalline nature of danazol with low diffraction intensities. With increased surface area and saturation solubility, the nanosuspensions showed enhanced dissolution velocity and oral bioavailability in rats when compared to the bulk danazol suspension. CONCLUSIONS: The results suggest that the preparation of nanosuspensions by WM or HPH is a promising approach to formulate new drugs or to reformulate existing drugs with poorly water-soluble properties.

Cannabidiol bioavailability after nasal and transdermal application: effect of permeation enhancers.

CONTEXT: The nonpsychoactive cannabinoid, cannabidiol (CBD), has great potential for the treatment of chronic and 'breakthrough' pain that may occur in certain conditions like cancer. To fulfill this goal, suitable noninvasive drug delivery systems need to be developed for CBD. Chronic pain relief can be best achieved through the transdermal route, whereas 'breakthrough' pain can be best alleviated with intranasal (IN) delivery. Combining IN and transdermal delivery for CBD may serve to provide patient needs-driven treatment in the form of a nonaddictive nonopioid therapy. OBJECTIVE: Herein we have evaluated the IN and transdermal delivery of CBD with and without permeation enhancers. MATERIALS AND METHODS: In vivo studies in rats and guinea pigs were carried out to assess nasal and transdermal permeation, respectively. RESULTS: CBD was absorbed intranasally within 10 minutes with a bioavailability of 34-46%, except with 100% polyethylene glycol formulation in rats. Bioavailability did not improve with enhancers. The steady-state plasma concentration of CBD in guinea pigs after transdermal gel application was 6.3 +/- 2.1 ng/mL, which was attained at 15.5 +/- 11.7 hours. The achievement of a significant steady-state plasma concentration indicates that CBD is useful for chronic pain treatment through this route of administration. The steady-state concentration increased by 3.7-fold in the presence of enhancer. A good in vitro and in vivo correlation existed for transdermal studies. CONCLUSION: The results of this study indicated that CBD could be successfully delivered through the IN and transdermal routes.

Comparison of artificial sebum with human and hamster sebum samples.

To understand drug delivery to the sebum filled hair and sebaceous follicles, it is essential to use an artificial sebum as a surrogate of the human sebum for the investigation of drug transport properties. Artificial sebum L was developed in-house based on the chemical similarity to human sebum. The partition and diffusion of model compounds (ethyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, and hexyl 4-hydroxybenzoate) were measured in human sebum, hamster ear and body sebum (a commonly used animal model), and four representative artificial sebum samples (N, S, F, and L) in which artificial sebums, N, S and F were selected based on the available literature. DSC and NMR studies were also conducted on all sebums to compare their melting properties and chemical compositions. In vitro studies show that the partition coefficients of the three model compounds in artificial sebum L were similar to that of human sebum, whereas the hamster ear and body sebum, and other three artificial sebum samples were different from that of human sebum. Additionally, the in vitro sebum flux (microg/(cm(2)min) of three model compounds through artificial sebum L was closer to that of human sebum when compared with the other three artificial sebum (N, S and F), hamster body and hamster ear sebum. The results of this study indicate that the artificial sebum L could be used as an alternative to human sebum, as the physicochemical properties of this artificial sebum is relatively similar to human sebum.

Investigation of drug partition property in artificial sebum.

Targeted delivery of a therapeutic agent into the hair and sebaceous follicles greatly depends on the extent of drug partitioning/diffusion in the sebum. The objective of the present research was to develop a method to determine the sebum partition coefficient in order to facilitate the selection of sebum-targeted drug candidates. Partition coefficients of model drugs with different chemical structures and 4-hydroxybenzoate series compounds were measured in artificial sebum/water (K(sebum)) and human stratum corneum/water (K(sc)) at 37 degrees C. The relationship was evaluated between logK(sebum), logK(sc) and clogP. The results of the partition coefficient studies indicate that the K(sebum) of some drugs was significantly higher than the K(sc), whereas some drugs showed lower or similar K(sebum) when compared with K(sc). Overall, a relatively poor correlation was observed between logK(sebum), logK(sc) and clog P. However, a linear relationship exists between logK(sebum) and clog P in the 4-hydroxybenzoate series compounds, indicating that K(sebum) depends on the lipophilicity and chemical structure of the compounds. The results of the present study demonstrate that K(sebum) is different from K(sc) and calculated P and is likely to be a critical parameter reflecting drug delivery into hair and sebaceous follicles.

Diffusion properties of model compounds in artificial sebum.

Sebaceous glands secrete an oily sebum into the hair follicle. Hence, it is necessary to understand the drug partition and diffusion properties in the sebum for the targeted delivery of therapeutic agents into the sebum-filled hair follicle. A new method was developed and used for determination of sebum flux of topical therapeutic agents and other model compounds. The drug transport through artificial sebum was conducted using sebum loaded filter (Transwell) as a membrane, drug suspensions as donor phases and HP-beta-CD buffer solution as a receiver phase. The experiment was performed at 37 degrees C for 2h. The results of the drug transport studies indicate that the flux (J(sebum)) through the artificial sebum is compound dependent and a bell-shaped curve was observed when logJ(s) versus alkyl side chain length of the compounds that proved to be different from the curves obtained upon plotting logJ skin versus clogP for the same compounds, indicating the possibility to select appropriate compounds for sebum targeted delivery based on the differences in the skin flux and sebum transport profiles of the molecules.

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.

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.

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.

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.

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.

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.

Intranasal delivery of recombinant human parathyroid hormone [hPTH (1-34)], teriparatide in rats.

The aim of this study was to explore the nasal route as an alternative to daily subcutaneous injections of hPTH (1-34). Anesthetized rats were surgically prepared and nasally dosed with aqueous solutions of hPTH (1-34). Plasma samples were assayed by radioimmunoassay and data generated fit to two-(intravenous) and one-(intranasal) compartment pharmacokinetic models using WinNonlin. The toxicity of hPTH (1-34) solution administered to the rats was assessed by screening its effect on transepithelial electrical resistance, potential difference, paracellular marker permeation, tissue viability, and protein leakage using the EpiAirway tissue model. The intranasal absorption of hPTH (1-34) was rapid; the absorption rate constants (alpha) were 33.2+/-24 h(-1) [without bovine serum albumin (BSA)] and 9.8+/-5.1 h(-1) (with 1% BSA). The maximum plasma concentrations (Cmax): 151+/-24 pg/mL (without BSA) and 176+/-37 (with 1% BSA) were attained within approximately 15 min. The intranasal bioavailabilities (Fabs) were 12.1+/-3.4% (without BSA) and 17.6+/-1.5% (with 1% BSA). The hPTH (1-34) formulation administered to the rats had no detrimental effect on the EpiAirway tissue epithelial electrical parameters and functional integrity. Based on the results of this study, the nasal route appears to be a prospective alternative to subcutaneous injections of hPTH (1-34).

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.

Transdermal delivery of the synthetic cannabinoid WIN 55,212-2: in vitro/in vivo correlation.

PURPOSE: The aim of the current investigation was to evaluate the percutaneous absorption of the synthetic cannabinoid WIN 55,212-2 in vitro and in vivo. METHODS: The in vitro permeation studies of WIN 55,212-2 in human skin, hairless guinea pig skin, a polymer membrane with adhesive, and a skin/polymer membrane composite were conducted in flowthrough diffusion cells. The pharmacokinetic parameters for WIN 55,212-2 were determined after intravenous administration and topical application of Hill Top Chambers and transdermal therapeutic systems (TTS) in guinea pigs. RESULTS: The in vitro permeation studies indicated that the flux of WIN 55,212-2 through hairless guinea pig skin was 1.2 times more than that through human skin. The flux of WIN 55,212-2 through human and guinea pig skin was not significantly higher than that through the corresponding skin/polymer membrane composites. The mean guinea pig steady-state plasma concentrations after topical 6.3 cm2 chamber and 14.5 cm2 TTS patch applications were 5.0 ng/ml and 8.6 ng/ml, respectively. CONCLUSIONS: The topical drug treatments provided significant steady-state plasma drug levels for 48 h. The observed in vivo results from the Hill Top Chambers and TTS patches in the guinea pigs were in good agreement with the predicted plasma concentrations from the in vitro data.

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.

In vitro/in vivo correlation studies for transdermal delta 8-THC development.

The present study was carried out in order to develop a transdermal therapeutic system (TTS) for Delta(8)-THC. The in vitro permeability studies of Delta(8)-THC in human skin and hairless guinea pig skin with and without a rate-controlling membrane were conducted in flow-through diffusion cells. Delta(8)-THC pharmacokinetic parameters were determined after topical application of transdermal patches and intravenous administration in guinea pigs. The in vitro results indicated that there was no significant difference in the mean flux or in the permeability coefficient of Delta(8)-THC in human skin versus hairless guinea pig skin. The flux of Delta(8)-THC through the human skin/membrane composite was not significantly lower than that through the hairless guinea pig skin/membrane composite; and the skin controlled the Delta(8)-THC delivery rate. Intravenous doses of Delta(8)-THC followed a two-compartment model with a significant distribution phase. On application of the TTS patch, the plasma concentration of Delta(8)-THC reached a mean steady-state level of 4.4 ng/mL within 1.4 h and was maintained for at least 48 h. Significant amounts of metabolites were observed in the plasma after topical application. The in vitro-study predicted plasma concentration following application of the transdermal patch was in agreement with the observed guinea pig plasma concentrations of Delta(8)-THC.

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.

Human skin permeation of Delta8-tetrahydrocannabinol, cannabidiol and cannabinol.

The purpose of this study was to quantify the in-vitro human skin transdermal flux of Delta8-tetrahydrocannabinol (Delta8-THC), cannabidiol (CBD) and cannabinol (CBN). These cannabinoids are of interest because they are likely candidates for transdermal combination therapy. Differential thermal analysis and in-vitro diffusion studies with human tissue were completed for the compounds. Heats of fusion, melting points and relative thermodynamic activities were determined for the crystalline compounds, CBD and CBN. Flux, permeability, tissue concentration and lag times were measured in the diffusion experiments. CBN had a lower heat of fusion and corresponding higher calculated relative thermodynamic activity than CBD. Ethanol concentrations of 30 to 33% significantly increased the transdermal flux of Delta8-THC and CBD. Tissue concentrations of Delta8-THC were significantly higher than for CBN. Lag times for CBD were significantly smaller than for CBN. The permeabilities of CBD and CBN were 10-fold higher than for Delta8-THC. Combinations of these cannabinoids with ethanol will be further studied in transdermal patch formulations in vitro and in vivo, as significant flux levels of all the drugs were obtained. CBD, the most polar of the three drugs, and other more polar cannabinoids will also be the focus of future drug design studies for improved transdermal delivery rates.