Improved ocular delivery of quercetin and resveratrol: A comparative study between binary and ternary cyclodextrin complexes.

The number of patients affected by Dry Eye Disease (DED) had notably increased worldwide, addressing the need of novel therapeutic approaches. Polyphenols, quercetin (QUE) and resveratrol (RSV) show necessary antioxidant and anti-inflammatory properties to manage DED, but their application as topical eyedrops is restricted by low aqueous solubility and low chemical stability. Cyclodextrins (CD) are widely used to improve physicochemical characteristics of drugs. Consequently, the aim of this study was to make a comparison between binary complexes with quercetin, resveratrol and cyclodextrins and tertiary complexes adding hyaluronic acid (HA). Both complexes were able to enhance solubility and stability of QUE and RSV. AFM imaging and DLS measurements disclose the formation of spherical nanoaggregates within tertiary complexes of both QUE and RSV with mean diameters of 103 and 82 nm. Neither complex demonstrated cytotoxic effect in in vitro studies in corneal (HCE) and conjunctival (IM-ConjEpi) cell lines. In HCE cells, complexes containing QUE or RSV at their highest concentrations were able to scavenge more than 95 % of the ROS that were produced intracellularly (p < 0.005). Similar response was observed with IM-ConjEpi cells. The antioxidant effect was maintained in the complexes with HA. This confirmed their potential as viable topical treatment for DED.

Effect of storage on the dissolution rate of a fast-dissolving perphenazine/ß-cyclodextrin complex.

OBJECTIVE: In general, the chemical and physical stability of amorphous cyclodextrin complexes and how storage affects their dissolution rate have not been widely reported. The aim of this study was to evaluate the solid-state stability of a fast-dissolving perphenazine/ß-cyclodextrin (ß-CD) complex, which has been found to be well absorbed after sublingual administration to rabbits. In addition, the dissolution rate of plain ß-CD in crystalline and amorphous forms was determined. METHODS: The amorphous perphenazine/ß-CD complex powders were prepared by spray-drying and freeze-drying, and their stability was examined after storage at 40°C, 75% relative humidity (RH) or at room temperature, 60% RH for up to 82 days. KEY FINDINGS: Perphenazine was found to be chemically stable in all samples. The dissolution rate of perphenazine remained practically unchanged at both storage conditions, although partial crystallization was observed in both spray-dried and freeze-dried samples at 40°C, 75% RH. Interestingly, it was also observed that the dissolution rates of crystalline and amorphous ß-CD were similar. CONCLUSION: The results suggest that CD complexation may represent a suitable alternative for preparing intraorally dissolving formulations because the fast dissolution rate of the drug was maintained even though changes in the crystal structure were observed during storage.

The effect of hydroxypropyl-beta-cyclodextrin and sucrose on the sublingual absorption of midazolam in rabbits.

Sublingually administered midazolam is commonly used for premedication of pediatric patients. However, the irritating taste and low aqueous solubility of midazolam complicate its sublingual use. Cyclodextrin complexation can be used to improve both the taste and aqueous solubility of drugs, but based on earlier studies, the complexation efficiency of midazolam is relatively low. In the present study, the complexation of midazolam with hydroxypropyl-beta-cyclodextrin (HP-ß-CD) was investigated in the presence of various excipients. The aqueous solubility of midazolam improved significantly when HP-ß-CD was used together with sucrose. Sucrose alone did not increase the solubility of midazolam. In addition, sucrose increased the apparent stability constant of the midazolam/HP-ß-CD complex. The pharmacokinetics of midazolam in different dosage forms was investigated in rabbits (dose 1mg/rabbit) after intravenous administration of midazolam solution and after sublingual administration of midazolam solution, midazolam/HP-ß-CD/sucrose solution or midazolam/HP-ß-CD/sucrose powder. Midazolam displayed rapid sublingual absorption (mean t(max) ≤30min from the liquid formulations and 60 min from the solid formulation) with high absolute bioavailability (>68%) from all evaluated formulations. Based on the results, HP-ß-CD and sucrose can be utilized together to prepare more concentrated and palatable midazolam formulations for sublingual administration in pediatric patients.

Determination of midazolam and 1-hydroxymidazolam from plasma by gas chromatography coupled to methane negative chemical ionization mass spectrometry after sublingual administration of midazolam.

A sensitive and selective gas chromatographic mass spectrometric method for the determination of midazolam and its biologically active metabolite, 1-hydroxymidazolam, in rabbit plasma has been developed and validated. Sample preparation includes mixed-mode solid-phase extraction and derivatization with silylating reagents. Midazolam-d4 was used as an internal standard for the determination of parent drug and its active metabolite. The instrumentation consisted of a capillary column gas chromatography and a single quadrupole mass spectrometer with a negative chemical ionization. The method was found to be valid in terms of selectivity, linearity, precision, accuracy, and recovery over the concentration range of 2-200 ng/ml and 1-100 ng/ml for midazolam and 1-hydroxymidazolam, respectively. For both analytes, the lower limit of quantification was 2 ng/ml. Midazolam was stable in stock solutions stored three months at -20°C and in human plasma stored for three months at -80°C. In addition, no degradation of midazolam was found after three freeze-thaw cycles, in short-term stability at room temperature for 24h, or in post-preparative stability in the autosampler. The validity of the method was further tested by performing a pharmacokinetic study of sublingual administration of midazolam in rabbits. The method will be used in studies related to a formulation development of novel midazolam formulations for use in paediatric anaesthesia.

Fast-dissolving sublingual solid dispersion and cyclodextrin complex increase the absorption of perphenazine in rabbits.

OBJECTIVES: The sublingual administration route as well as solid dispersion formation with macrogol 8000 and complexation with ß-cyclodextrin (ß-CyD) were investigated as ways for improving the absorption of perphenazine, a poorly water-soluble drug subjected to substantial first-pass metabolism. METHODS: The absorption of perphenazine was studied in rabbits after sublingual administration of perphenazine/macrogol solid dispersion, solid perphenazine/ß-CyD complex and plain micronized perphenazine, as well as after peroral administration of an aqueous perphenazine solution. Solid formulations were prepared by freeze-drying (perphenazine/macrogol solid dispersion) or spray-drying (perphenazine/ß-CyD complex). KEY FINDINGS: The value for area under the curve from 0 to 360 min (AUC(0-360 min) ) of perphenazine after peroral administration was only 8% of the AUC(0-360 min) value obtained after intravenous administration, while the corresponding values for the sublingually administered formulations were 53% (perphenazine/macrogol solid dispersion), 41% (perphenazine/ß-CyD complex) and 64% (micronized perphenazine). There are three possible mechanisms to explain these results: avoidance of the first-pass metabolism; good sublingual absorption of perphenazine; and rapid dissolution rate of perphenazine from the studied formulations. CONCLUSIONS: With sublingual administration, the drug has to dissolve rapidly in a small volume of saliva. Based on the present absorption studies in rabbits, the solid dispersion preparation and cyclodextrin complexation were postulated to be useful ways to attain successful sublingual administration of perphenazine. Good sublingual absorption was also achieved by micronization of perphenazine. As far as we are aware, this paper is one of the first to evaluate the sublingual administration of a solid dispersion in vivo.

An optical method for continuous monitoring of the dissolution rate of pharmaceutical powders.

Monitoring systems providing fast and reliable, even on-line data, from a distinct process stage or final product are needed in drug development, from the early stages of drug discovery until the drug product manufacturing procedures. This includes also processes involving solid particles, such as drug dissolution. However, the existing in vitro drug dissolution test methods suffer limitations, such as long sampling times of 30-60s and thus the inability to be adapted to continuous monitoring, time consuming sample preparation and consumption of large amounts of reagents. In this study, an optical method for monitoring the dissolution rate of pharmaceutical powders was evaluated with model drugs having different dissolution rates. The measuring system consisted of a laser source, light detector, oscilloscope, magnetic stirrer and sample vessel. The intensity of laser light transmitted through the dissolution medium was recorded and displayed by the oscilloscope. Dissolution curves were produced by fitting the raw data with mathematical functions. The optical method was found to be resource-saving, reliable and capable of detecting differences in even rapid dissolution rates of drug compounds. This technique might have targets of application in real-time monitoring of processes in many different sectors, including the pharmaceutical industry.

Preparation and physicochemical characterization of a novel water-soluble prodrug of carbamazepine.

N-acyl-urea derivatives of carbamazepine (CBZ) were synthesized through the reactions of iminostilbene with acyl-isocyanates to form N-glycyl-carbamazepine (N-Gly-CBZ, after a deprotection step) or N-acetyl-carbamazepine (N-acetyl-CBZ). N-Gly-CBZ was isolated as its water-soluble HCl salt and was designed to act as a prodrug and convert to CBZ and glycine in vivo by enzymatic cleavage of the acyl-urea bond. The stability pH-rate profiles for N-Gly-CBZ and N-acetyl-CBZ were determined. The stability of N-Gly-CBZ was found to range over four orders of magnitude with its greatest stability at pH 3-4 and a t(90) value of 5.9 day at pH 4 at 25 degrees C. From the fit of the pH rate profile two pK(a) values were estimated to be 7.2 (terminal amine) and 10.0 (imide), which were independently verified using UV-visible spectroscopic analysis. The solubility of N-Gly-CBZ in aqueous solution was determined in the range of pH 5.5-7.5. The intrinsic solubility of the neutral form of the prodrug was found to be 4.4 mg/mL, and the solubility of the prodrug increased exponentially (log linear) as pH was decreased below its pK(a1) value. N-Gly-CBZ was found to have an aqueous solubility in excess of 50 mg/mL at pH 4. The presence of N-Gly-CBZ was found to increase the aqueous solubility of CBZ, a degradation product. CBZ showed an 8.6-fold greater solubility in an aqueous solution containing 23 mg/mL of N-Gly-CBZ than in water alone. The solubilization of CBZ by N-Gly-CBZ was investigated by examining the diffusion coefficients of the predominant species in D(2)O and was found to be more consistent with stacking complex formation than micelle formation. The stability of N-Gly-CBZ makes a ready-to-use parenteral formulation impractical, but a freeze-dried preparation for reconstitution appears to be feasible.

Cyclodextrins and chitosan derivatives in sublingual delivery of low solubility peptides: A study using cyclosporin A, alpha-cyclodextrin and quaternary chitosan N-betainate.

Systemic drug delivery through intraoral membranes may offer a promising administration route for lipophilic peptide drugs. The aim of the present study was to investigate the effect of alpha-cyclodextrin (alpha-CD) and a novel chitosan derivative, chitosan N-betainate (CH), on sublingual absorption of a hydrophobic model peptide cyclosporin A (CsA), and the effect of temperature on the complexation of CsA with alpha-CD. Complexation of CsA with alpha-CD was studied using the phase-solubility method. Sublingual absorption of CsA was studied by administration of solid CsA/alpha-CD complex (with and without CH solution), solid CsA/alpha-CD/CH formulation and solid plain CsA to rabbits. The solubility of CsA in aqueous alpha-CD solution (14%) increased with decreasing temperature; the solubility of CsA at room temperature, +5 and +1 degrees C was 1.2, 12 and 19mg/ml, respectively. The bioavailability of CsA after administration of plain CsA, solid CsA/alpha-CD and solid CsA/alpha-CD/CH (0.6+/-0.5, 1.4+/-0.7 and 1.7+/-0.8%, respectively; mean+/-S.D.) was further increased when solid CsA/alpha-CD was administered together with CH solution (3.2+/-2.2%). The present study shows that decreased temperature can be effectively utilized to produce CsA/alpha-CD complexes. It was also shown that alpha-CD and CH may be advantageous in sublingual delivery of lipophilic peptides, although the absolute bioavailability remains low.

The stability and dissolution properties of solid glucagon/gamma-cyclodextrin powder.

In the present study, the solid-state stability and the dissolution of glucagon/gamma-cyclodextrin and glucagon/lactose powders were evaluated. Freeze-dried powders were stored at an increased temperature and/or humidity for up to 39 weeks. Pre-weighed samples were withdrawn at pre-determined intervals and analyzed with HPLC-UV (HPLC=high performance liquid chromatography, UV=ultraviolet), HPLC-ESI-MS (ESI-MS=electrospray ionization mass spectrometry), SEC (size-exclusion chromatography), turbidity measurements and solid-state FTIR (Fourier Transform Infrared Spectroscopy). Dissolution of glucagon was evaluated at pH 2.5, 5.0 and 7.0. In addition, before storage, proton rotating-frame relaxation experiments of solid glucagon/gamma-cyclodextrin powder were conducted with CPMAS ((13)C cross-polarization magic-angle spinning) NMR (nuclear magnetic resonance) spectroscopy. In the solid state, glucagon was degraded via oxidation and aggregation and in the presence of lactose via the Maillard reaction. The solid-state stability of glucagon/gamma-cyclodextrin powder was better than that of glucagon/lactose powder. In addition, gamma-cyclodextrin improved the dissolution of glucagon at pH 5.0 and 7.0 and delayed the aggregation of glucagon after its dissolution at pH 2.5, 5.0 and 7.0. There was no marked difference between the proton rotating-frame relaxation times of pure glucagon and gamma-cyclodextrin, and thus, the presence of inclusion complexes in the solid state could not be ascertained by CPMAS NMR. In conclusion, when compared to glucagon/lactose powder, glucagon/gamma-cyclodextrin powder exhibited better solid-state stability and more favorable dissolution properties.

Development and validation of a gas chromatographic-mass spectrometric method for quantitative determination of perphenazine in rabbit plasma after sublingual administration.

Perphenazine is a phenothiazine-type antipsychotic that is a potential candidate for sublingual administration due to its extensive first-pass metabolism. In this study, a gas chromatographic-mass spectrometric method was developed for quantification of perphenazine in rabbit plasma after sublingual administration. The plasma samples were purified by mixed-mode solid phase extraction with good recovery (>83%). The method was linear (r(2)>0.99) over a range of 2-64 ng/ml, with a lower limit of quantification of 2 ng/ml. The accuracy was 100+/-4%, and the within-day and between-day precisions were <6.8% R.S.D. and <14% R.S.D., respectively. Perphenazine was stable in stock solutions and plasma. The method was successfully applied for analysing perphenazine in plasma after sublingual administration to rabbits.

Quantitative analysis of natural cyclodextrins by high-performance liquid chromatography with pulsed amperometric detection: application to cell permeation study.

Simple HPLC-PAD methods were developed for quantitation of cyclodextrins (CDs) in aqueous matrices from in vitro cell permeation studies. C-18 solid-phase extraction was used for sample pretreatment. Samples were analysed using acetonitrile-water mobile phase with post-column alkalization by 0.5M NaOH. Zorbax SB-Aq (for alpha-CD) and Zorbax SB-Phenyl (for beta-CD and gamma-CD) columns gave excellent peak shape and sufficient resolution of CD to glucose (2.7-3.2). The methods showed good concentration-response relationship (r > or = 0.999), precision (RSD% 0.7-5.1), repeatability (RSD% 3.4-13.7) and accuracy (87-107%). The limits of quantitation were 0.78, 0.46 and 0.52 microg/ml for alpha-CD, beta-CD and gamma-CD (RSD% of 10.6, 8.1 and 16.3, respectively).

In vitro toxicity and permeation of cyclodextrins in Calu-3 cells.

Cyclodextrins (CDs) can improve the pulmonary drug delivery by increasing aqueous solubility, absorption and bioavailability of drugs. Although the systemic absorption of CDs from gastrointestinal tract is very limited, their systemic absorption after pulmonary administration cannot be excluded. The aims of this study were 1) to evaluate the in vitro toxicity of various CDs (alpha-, beta-, gamma-, hydroxypropyl-alpha-, hydroxypropyl-beta- and randomly methylated-beta-CD) in pulmonary Calu-3 cells and Calu-3 cell layers using MTT and LDH cytotoxicity tests, and 2) to study the permeation of natural CDs (alpha-, beta- and gamma-CD) at non-toxic concentrations across Calu-3 cell layers. Randomly methylated-beta-CD evoked cell death and membrane damage in Calu-3 cells at lower concentrations compared to the other CDs tested. In terms of their toxicity, gamma-CD, hydroxypropyl-beta-CD and hydroxypropyl-alpha-CD were the safest to the Calu-3 cells. Based on the cumulative penetrated amount at 4 h, the apparent permeability coefficients for alpha-, beta- and gamma-CD were 6.77+/-2.23 x 10(-8), 6.68+/-0.84 x 10(-8) and 6.71+/-0.74 x 10(-8) cm/s, respectively. In conclusion, this study indicates that 1) in terms of their local safety, hydroxypropylated CDs and natural gamma-CD seem to be the safest of the tested CDs in pulmonary drug delivery, and 2) cyclodextrins may be absorbed into the systemic circulation from the lungs.

The effect of cyclodextrins on chemical and physical stability of glucagon and characterization of glucagon/gamma-CD inclusion complexes.

The purpose of the study was to evaluate the effect of cyclodextrin (CD) complexation on the chemical and physical stability of a polypeptide hormone glucagon and to study the interactions between glucagon and gamma-cyclodextrin molecules in inclusion complexes. The chemical stability of glucagon at pH 2.0 was studied with HPLC-UV and HPLC-MS/MS. The physical stability of glucagon at pH 2.5 was studied by measuring the turbidity (A(405 nm)) and viscosity (Ostwald capillary viscosimeter) of the samples. The structure of glucagon/gamma-CD complexes at pH 2.5 was studied with 2D-NMR. The presence of various CDs increased the chemical half-life of glucagon at pH 2.0 (37 degrees C, 0.01 M HCl, ionic strength 0.15) and prolonged the lag-time before aggregation at pH 2.5 (0.9% (w/v) NaCl in 3.2 mM HCl). The NMR studies showed that the side chains of all the aromatic amino acid residues (Phe6, Tyr10, Tyr13, Phe22, Trp25) and leucines (Leu14 and Leu26) of glucagon interacted with the cavities of the gamma-CD molecules. The present study shows that glucagon forms inclusion complexes with cyclodextrins in acidic solution, resulting in an improvement in its chemical and physical stability.

Crystal structure changes of gamma-cyclodextrin after the SEDS process in supercritical carbon dioxide affect the dissolution rate of complexed budesonide.

PURPOSE: The present study describes the crystal structure changes of gamma-cyclodextrin (gamma-CD) during the solution enhanced dispersion by supercritical fluids (SEDS) process and its effect on dissolution behaviour of complexed budesonide. MATERIALS AND METHODS: gamma-CD solution (10 mg/ml in 50% ethanol) was pumped together with supercritical carbon dioxide through a coaxial nozzle with or without a model drug, budesonide (3.3 mg/ml). The processing conditions were 100 b and 40, 60 or 80 degrees C. gamma-CD powders were characterised before and after vacuum-drying (2-3 days at RT) with XRPD, SEM and NMR. Budesonide/gamma-CD complexation was confirmed with DSC and XRPD. The dissolution behaviour of complexed budesonide was determined in aqueous solution (1% gamma-CD, 37 degrees C, 100 rpm). RESULTS: During the SEDS process (100 b, 40 and 60 degrees C), gamma-CD and budesonide/gamma-CD complexes crystallized in a tetragonal channel-type form. The vacuum-drying transformed crystalline gamma-CD into amorphous form while the complexes underwent a tetragonal-to-hexagonal phase transition. The increase in the processing temperature decreased the crystallinity of gamma-CD. At 80 degrees C, amorphous gamma-CD was obtained while the complexes crystallized in a hexagonal channel-type form. The dissolution behaviour of budesonide/gamma-CD complexes was dependent on their crystal structure: the tetragonal form dissolved faster than the hexagonal form. CONCLUSIONS: The crystal structure of gamma-CD and subsequently, the dissolution rate of complexed budesonide, can be modified with the processing conditions.

Precipitation complexation method produces cannabidiol/beta-cyclodextrin inclusion complex suitable for sublingual administration of cannabidiol.

In the present study, the precipitation complexation method was used to prepare a complex of cannabidiol (CBD) with beta-CD. The effect of beta-CD-complexation on the sublingual absorption of CBD was studied in rabbits. A solid CBD/beta-CD inclusion complex was prepared by precipitation and the effect of complex formation on the dissolution rate of CBD was studied. The absorption of CBD (a 250 microg/kg dose of CBD in all formulations) after sublingual administration of solid CBD/beta-CD complex and ethanolic CBD solution, and after oral administration of ethanolic CBD solution, was studied in vivo in rabbits. The dissolution rate of solid CBD/beta-CD complex in vitro was significantly (p<0.05) higher than that of plain CBD. The absorption of CBD (AUC0-300 min) decreased in the following order: sublingual ethanolic CBD solution (420+/-120 ngxmin/mL; mean+/-SD; n=4)>sublingual solid CBD/beta-CD complex (270+/-120 ngxmin/mL)>oral ethanolic CBD solution (concentrations in plasma below the quantitation limit). The results demonstrate that sublingual administration of a solid CBD/beta-CD complex enhances the absorption of CBD in rabbits when compared to oral administration of ethanolic CBD. Furthermore, the solid CBD/beta-CD complex may provide an alternative formulation for sublingual administration of CBD.

Preparation of budesonide/gamma-cyclodextrin complexes in supercritical fluids with a novel SEDS method.

The aim was to investigate if solid drug/cyclodextrin complexes could be produced in a single-step process with a solution enhanced dispersion by supercritical fluids (SEDS) method. Budesonide and gamma-cyclodextrin (CD) solutions (50% or 99.5% ethanol) were pumped from the same (conventional method) or separate (modified method) containers together with supercritical carbon dioxide through a coaxial nozzle into a particle formation chamber. The pressure was maintained at 100, 150 or 200 bar with a temperature of 40, 60 or 80 degrees C. SEDS-processed powders were characterised with HPLC, DSC and XRPD for budesonide content, complexation and crystallinity. The budesonide dissolution rate was determined in 1% gamma-CD aqueous solution. Solid, white budesonide/gamma-CD complex particles were formed using the conventional and modified SEDS processes. The complexation efficiency was dependent on the processing conditions. For example, with the conventional method (100 bar, 60 degrees C) the yield of the powder was 65+/-12% with 0.14+/-0.02 mg budesonide/mg powder, corresponding to 1:2 drug:CD molar ratio. The dissolution rate of this complexed budesonide (93+/-2% after 15 min) was markedly higher compared to unprocessed micronised budesonide (41+/-10%) and SEDS-processed budesonide without CD (61+/-3%). As a conclusion, SEDS is a novel method to produce solid drug/CD complexes in a single-step process.

Sublingual administration of Delta9-tetrahydrocannabinol/beta-cyclodextrin complex increases the bioavailability of Delta9-tetrahydrocannabinol in rabbits.

The bioavailability of Delta(9)-tetrahydrocannabinol (THC) was determined after its sublingual administration as solid THC/beta-cyclodextrin (THC/beta-CD) complex, and was compared to oral administration of ethanolic THC, in rabbits. The absolute bioavailability of THC after sublingual administration of solid THC/beta-CD complex powder (16.0 +/- 7.5%; mean +/- SD; n = 4) is higher than the bioavailability of THC after oral administration of ethanolic THC solution (1.3 +/- 1.4%; mean +/- SD; n = 4). The results suggest that sublingual administration of THC/beta-CD complex is a useful tool in improving absolute bioavailability of THC.

Cyclodextrins in drug delivery.

Cyclodextrins are a family of cyclic oligosaccharides with a hydrophilic outer surface and a lipophilic central cavity. Cyclodextrin molecules are relatively large with a number of hydrogen donors and acceptors and, thus, in general they do not permeate lipophilic membranes. In the pharmaceutical industry cyclodextrins have mainly been used as complexing agents to increase aqueous solubility of poorly soluble drugs, and to increase their bioavailability and stability. Studies in both humans and animals have shown that cyclodextrins can be used to improve drug delivery from almost any type of drug formulation. However, the addition of cyclodextrins to existing formulations without further optimisation will seldom result in acceptable outcome. Currently there are approximately 30 different pharmaceutical products worldwide containing drug/cyclodextrin complexes on the market.

Effects of RM-beta-CD on sublingual bioavailability of Delta9-tetrahydrocannabinol in rabbits.

The purpose of the present study was to develop novel cyclodextrin-containing sublingual formulations of cannabinoids. Complexation of model cannabinoids, Delta(9)-tetrahydrocannabinol (THC) and cannabidiol (CBD), with randomly methylated beta-cyclodextrin (RM-beta-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD), were studied by the phase-solubility method. Due to better complexation efficiency, RM-beta-CD was selected for further studies. Solid THC/RM-beta-CD and CBD/RM-beta-CD complexes were prepared by freeze-drying. The dissolutions of both THC and CBD in the presence and absence of RM-beta-CD were determined. THC was selected for in vivo studies: the pharmacokinetics of THC after both sublingual and oral administrations of ethanolic THC and THC/RM-beta-CD complex solutions were studied in rabbits. The aqueous solubility of CBD and THC increased as a function of CD concentration, showing A(L)- and A(P)-type diagrams for HP-beta-CD and RM-beta-CD, respectively. Dissolution rates of THC/RM-beta-CD and CBD/RM-beta-CD complexes were significantly (p < 0.05) higher than those of plain THC and plain CBD, respectively. The absolute bioavailability (F) of THC decreased in the following order: sublingual THC/RM-beta-CD solution (F = 12.1+/-1.4%; mean+/-S.D.; n = 4) > oral THC/RM-beta-CD solution (F = 4.0+/-6.0%) > or = sublingual ethanolic THC solution (F = 3.8+/-2.8%) > oral ethanolic THC solution (F = 1.3+/-1.4%). These results demonstrate that RM-beta-CD increases both the aqueous solubility and dissolution rate of these cannabinoids, making the development of novel sublingual formulation possible. These results also suggest that the sublingual administration of a THC/RM-beta-CD complex substantially increases the bioavailability of THC in rabbits.

Determination of Delta9-tetrahydrocannabinol from rabbit plasma by gas chromatography-mass spectrometry using two ionization techniques.

The purpose of the study was to develop a gas chromatography-mass spectrometric (GC-MS) method for the identification and quantitation of Delta(9)-tetrahydrocannabinol (THC) in rabbit plasma. Two ionization techniques were utilized for GC-MS: electron impact ionization (EI) after i.v. administration and negative chemical ionization (NCI) after sublingual administration. THC was isolated from plasma by solid phase extraction and derivatized by either trimethylsilylation (EI) or trifuoroacetylation (NCI), with deuterated THC as an internal standard. The validity of analytical method was confirmed by investigating selectivity, limit of quantitation, linearity, accuracy, precision, recovery and stability of the analyte. The method proved to be selective, linear, accurate and precise over a range of 10-430 and 0.3-530 ng/ml of THC in plasma for EI and NCI, respectively. The extraction recovery was >81% for each concentration level studied, and the analyte was shown to be stable during storage and sample preparation. The method was applied successfully in analysing THC from rabbit plasma.