Transdermal delivery of propranolol using mixed grades of Eudragit: design and in vitro and in vivo evaluation

A matrix-dispersion-type transdermal drug delivery system of propranol was developed using different ratios of mixed polymeric grades of Eudragit. Formulations were evaluated for in vitro dissolution characteristics using a Cygnus' sandwich patch holder. Selected formulations followed zero-order release kinetics. In vivo evaluation was carried out on healthy human volunteers following a balanced incomplete block design (BIBD). In vitro dissolution rate constant k and pharmacokinetic parameters generated from plasma and urine were evaluated statistically. Statistically excellent correlation was found between percentages of drug absorbed from patch versus C_max, AUC_0-24, and AUC_0-∞. A highly significant difference was observed when C_max and AUC_0- generated from plasma and urine data were compared, but when k_e, t_1/2e, k_a, t_1/2awere compared, the difference was not significant. Urinary excretion data are suggested as a simpler alternative to blood-level data in studying the kinetics of absorption and deriving the absorption parameter.     

Steady-State Pharmacokinetics of a Multiparticulate Matrix Sustained-Release Theophylline Preparation

A novel multiparticulate matrix sustained-release theophylline preparation was evaluated in comparison with a reference product, Neulin-SR®, in a multiple-dose administration study, conducted according to a randomized, two-way crossover design involving 12 healthy volunteers. Comparison was made using the parameters, area under the serum concentration-time curve from time 0 to 12 hr (AUC_0-12), time to reach peak serum concentration (T_max), peak serum concentration (C_max), trough serum concentration (C_min), average drug concentration (C_av), degree of fluctuation (DF), percentage of time serum drug concentrations lie within the therapeutic range (occupancy time) and time for 50% of dose absorbed (T_50%). The parameters, C_max, C_min, AUC_0-12 C_av, and DF were logarithmic transformed prior to statistical analysis. A statistically significant difference was obtained between the values of the two preparations in the T_max, C_min, DF, and T_50%; but not in the C_max, AUC_0-12, C_av, and occupancy time. These findings suggest that the novel preparation has a more sustained rate but equivalent extent of absorption compared to Neulin-SR, leading to a more uniform steady-state serum profile.     

In Vivo Bioavailability of a Multiparticulate Matrix Sustained-Release Theophylline Preparation Under Fed and Fasted Conditions

The in vivo bioavailability of a novel multiparticulate matrix sustained-release theophylline preparation was compared under fed and fasted conditions. Twelve healthy volunteers participated in the study conducted according to a randomized, two-way crossover design. The parameters used for the comparison were: total area under the serum concentration-time curve (AUC₀), time to reach peak serum concentration (T_max), and peak serum concentration (C_max). No statistically signifcant difference was observed bemeen the fed and fasted logarithmic transformed values of AUCG₀ and C_max as well as the fed and fasted values of T_max In addition, the 90% confidence interval for the ratio of logarithmic transformed AUC₀ values of the fed condition over those of the fasted was calculated to lie between 0.90 and 1.04, which is within the bioequivalence limit of 0.80-1.25. These findings indicate that both the rate and extent of absorption of the novel preparation were not significantly affected by food, although a lag time in absorption was observed in the fed condition     

Evaluation of bioequivalence of two formulations containing 100 milligrams of aceclofenac

The bioequivalence of two oral formulations containing aceclofenac 100 mg was determined in 24 healthy Indian male volunteers. The study was designed as a single dose, fasting, two-period two-sequence crossover study with a washout period of 1 week. The content of aceclofenac in plasma was determined by a validated HPLC method with UV detection. The preparations were compared using the parameters area under the plasma concentration-time curve (AUC_0-t), area under the plasma concentration-time curve from zero to infinity (AUC_0-∞), peak plasma concentration (C_max), and time to reach peak plasma concentration (t_max). No statistically significant difference was observed between the logarithmic transformed AUC_0-∞ and C_max values of the two preparations. The 90% confidence interval for the ratio of the logarithmic transformed AUC_0-t, AUC_0-∞, and C_max were within the bioequivalence limit of 0.80-1.25.     

In vitro-in vivo correlation and comparative bioavailablity of vincamine in prolonged-release preparations

Developing an in vitro dissolution test that gives good correlation with in vivo data for a particular drug product is an important objective. Available dissolution data of vincamine prolonged-release preparations show different in vitro release behavior at different pH using the conventional dissolution techniques. This does not allow development of an in vitro-in vivo correlation (IVIVC). In the present work, the flow-through cell (FTC) dissolution system (USP apparatus 4) was utilized to compare the release rate of three marketed prolonged-release oral formulations of vincamine; namely, a brand innovator formulation used as the reference and two formulations from different manufacturers as test products. Both the open and closed systems of FTC were used at variable pH. A comparative bioavailability study was then conducted in 16 healthy volunteers for a test versus the reference product by administering a single dose of 60 mg in a crossover design. Vincamine plasma concentrations were analyzed by a sensitive high-performance liquid chromatography (HPLC) method. This was followed by assessment of IVIVC according to level A as specified by USP 23; the absorbed fraction of vincamine was determined using the Wagner-Nelson method. The results indicated that the pH of the medium affects the release rate pronouncedly. The relative bioavailability based on C_max and AUC_0-12 were found to be 83.15% and 84.15%, respectively. Good correlation was obtained between fraction absorbed in vivo and fraction dissolved in vitro by applying the open system of the FTC. This technique gave the most favorable results with regard to the percentage vincamine released and the IVIVC     

Transdermal Absorption of Zidovudine from Ethanol-Isopropyl Myristate Mixed System and Influence of Probenecid on It in Rats

Transdermal absorption of zidovudine (AZT) from an ethanol-isopropyl myristate (IPM) mixed system was examined in rats. For comparison of bioavailability (BA) after topical applications, 0.25 ml of the ethanol/IPM system containing 40% ethanol and 60 mM AZT was applied as a standard formulation. Values of the area under the plasma concentration-time curves of AZT for 8 hr (AUC_0-8), as indices of BA, following application of various formulations were compared with that of the standard formulation. Then the influence of content of the drug and ethanol, and application volume of the system was evaluated. BA was effectively improved only when the total amount of ethanol applied on the skin was increased. On the other hand, simultaneous transdermal application of AZT and probenecid increased the AU_0-8, of AZT without necessitating the increase in ethanol content in the formulation. In addition, coadministered probenecid improved cerebrospinal fluid/plasma concentration ratio of AZT.     

Average bioequivalence of clarithromycin immediate released tablet formulations in healthy male volunteers

The objective of this study was to assess average bioequivalence of two immediate released tablet formulations of 500-mg clarithromycin tablets in 24 healthy Thai male volunteers. In a randomized, single dose, fasting state, two-period, crossover study design with a 1-week washout period, each subject received a 500-mg clarithromycin tablet. Plasma samples were collected over a 24-hour period after oral administration and were analyzed by using a validated method using high performance liquid chromatography with electrochemical detection. Pharmacokinetic parameters were determined by using noncompartmental analysis. The time to reach the maximal concentration (t_max, h), the peak concentration (C_max, ng/mL), and the area under the curve (AUC_{0 - ∞}, ng.h/mL) of the Reference and Test formulations were 2.0 ± 0.8 vs. 2.2 ± 0.9, 2793 ± 1338 vs. 2642 ± 1344, and 17912 ± 7360 vs. 17660 ± 7992, respectively. Relative bioavailability was 0.99. The 90% confidence interval of C_max and AUC_{0 - ∞} were 82.6-112.1% and 84.7-112.0%. Bioequivalence between the Test and Reference formulation can be concluded.     

Relationship Between Dissolution Rate and Bioavailability of Sustained-Release Ibuprofen Capsules

Dissolution studies of three marketed brands of ibuprofen sustained-release (SR) capsules were conducted on USP XIX dissolution apparatus 1, using buffers simulating the gastrointestinal tract (GIT) pHs. The products showed almost identical drug release pattern in dissolution studies. A single-dose crossover oral bioavailability study revealed statistically significant differences in C_max, T_max, AUC and percent bioavailability values among the SR products but no such differences are evident in the t_1/2a, K_a, t_1/2e, and K_e. Retard quotient values were used to evaluate the sustained-release nature of the products. Statistical moment parameters such as MRT, MAT, and MDT were related with the dissolution parameters. Statistically significant correlations were observed between MRT_{in vitro} and MRT_{in vivo} or MDT_{in vivo} T_50% and T_max; and T_90%, and C_max, or AUC¹²₀. The determination of MRT_{in vitro}, T_50%, and T_90%, may be useful as quality control parameters to which each batch of the ibuprofen SR products could be submitted.     

Comparative study on the bioequivalence of two formulations of pioglitazone tablet in healthy Thai male volunteers

The bioequivalence study of two 30 mg pioglitazone formulations was determined in healthy Thai male volunteers after a single dose administration in a randomized cross-over study with a 1-week washout period. Due to the high variability of the rate and extent of absorption of pioglitazone, an add-on subject study was required to assess bioequivalence. Reference product (Actos®, Takeda Chemical Industries, Ltd., Osaka, Japan) and test product (Glubosil®, Silom Medical Co. Ltd., Bangkok, Thailand) were given to 35 volunteers after overnight fasting. Blood samples were collected at specified time intervals. Plasma was analyzed for pioglitazone concentration using a validated HPLC method. Pharmacokinetic parameters were compared between test and reference products from plasma concentration-time profile by using non-compartment analysis. The statistical comparison of C_max and AUC_0-t, AUC_t-∞ clearly indicated that no significant difference in two products of pioglitazone tablets in add-on subject study. The 90% confidence intervals for the mean ratio (test/reference) of C_max and AUC_0-t, AUC_t-∞ were within the Thailand Food and Drug Administration acceptance range. Based on the pharmacokinetic and statistical results of this study, we can conclude that Glubosil® is bioequivalent to Actos®, and that two products can be considered interchangeable in medical practice.     

Influence of hydroxypropyl methylcellulose mixture,apparent viscosity,and tablet hardness on drug release using a 2(3) full factorial design

This study investigates the effects of three factors: (1) use of a mixture of two different grades of hydroxypropyl methylcellulose (HPMC), (2) apparent viscosity, and (3) tablet hardness on drug release profiles of extended-release matrix tablets. The lot-to-lot apparent viscosity difference of HPMC K15M on in vitro dissolution was also investigated. Four test formulations were made, each containing 10% of a very water-soluble active pharmaceutical ingredient (API), 32% HPMC K15M, or a mixture of HPMC K100LV and HPMC K100M, 56% diluents, and 2% lubricants. Each formulation was made at two hardness levels. A 2³ full factorial design was used to study various combinations of the three factors using eight experiments conducted in a randomized order. Dissolution studies were performed in USP apparatus I. The values of t_50% (time in which 50% drug is released) and t_lag (lag time, the time taken by the matrix tablet edges to get hydrated and achieve a state of quasi-equilibrium before erosion and the advance of solvent front through the matrix occur) were calculated from each dissolution profile. The similarity factor (f₂) was also calculated for each dissolution profile against the target dissolution profile. A simple Higuchi-type equation was used to analyze the drug release profiles. Statistical analysis using analysis of variance (ANOVA) and similarity factor (f₂) values calculated from the data indicated no significant difference among the t_50% values and dissolution profiles respectively for all formulations. Within the 3.3-6 kp hardness range investigated, dissolution rates were found to be independent of tablet hardness for all the formulations. Although significantly shorter lag times were observed for the tablets formulated with low- and high-viscosity HPMC mixtures in comparison to those containing a single grade of HPMC, this change had no significant impact on the overall dissolution profiles indicated by the similarity factor f₂ values. From this study it can be concluded that lot-to-lot variability in apparent viscosity of HPMC should not be a concern in achieving similar dissolution profiles. Also, results indicated that within the viscosity range studied (12,000-19,500 cps) an HPMC mixture of two viscosity grades can be substituted for another HPMC grade if the apparent viscosity is comparable. Also, the drug release is diffusion-controlled and depends mostly on the viscosity of the gel layer formed.     

Thermodynamic Properties and Hydrogen Accumulation Ability of Fullerene Hydride C60H36

Thermodynamic properties of fullerene hydride C₆₀H₃₆ in the ideal-gas and crystal states were studied by theoretical methods. Molecular structures and vibration frequencies were calculated for 9 isomers of C₆₀H₃₆ by the density functional theory (DFT) by use of a combination of the B3LYP functional with 6-31G* basis sets. Ideal-gas thermodynamic properties were calculated based on those parameters. Enthalpies of formation of C₆₀H₃₆ isomers in the ideal-gas state were derived from homodesmic reactions involving adamantane, cyclohexane, and C₆₀ fullerene. Using the standard methods of statistical mechanics, heat capacity and derived thermodynamic properties of crystalline C₆₀H₃₆ were calculated at 340-1000 K that extended the range of experimental measurements. With a crystal-gas heat capacity difference, the experimental value of sublimation enthalpy was extrapolated to room temperature as Δ_subH_m^o (298.15 K)=(193±10) kJ · mol^-1. Combining this value with the known experimental enthalpy of formation in the crystalline state, the ideal-gas enthalpy of formation of C₆₀H₃₆ at the synthesized sample isomer composition was obtained: Δ_f H_m^o (298.15 K)=(1206±28) kJ · mol^-1. Equilibrium constants and compositions were calculated for the reactions of hydrogenation of C₆₀ fullerene in different states. It was shown that C₆₀ can act as a hydrogen accumulator.     

Pharmacokinetic Interaction Between Dapsone and Rifampicin in Leprosy Patients

Different pharmacokinetic parameters of dapsone and rifampicin following P. O. administration of dapsone 100 mg. alone, rifampicin 600 mg. alone and dapsone 100 mg. plus rifampicin 600 mg. in 7 cases of untreated patients of leprosy were investigated. The blood levels, half-life and AUC_{0-8 hrs.} of dapsone were significantly reduced with simultaneous increase in plasma clearance when it was administered along with rifampicin. The pharmacokinetic behaviour of rifampicin was, however, not significantly affected in the presence of dapsone.     

Formulation design of a highly hygroscopic drug (pyridostigmine bromide) for its hygroscopic character improvement and investigation of in vitro/in vivo dissolution properties

Pyridostigmine bromide (PB) sustained-release (SR) pellets were developed by extrusion-spheronization and fluid-bed methods using Taguchi experimental and 2³ full factorial design. In vitro studies, the 2³ full factorial design was utilized to search for the optimal SR pellets with specific release rate at different time intervals (release percent of 2, 6, 12, and 24 hr were 6.24, 33.48, 75.18, and 95.26%, respectively) which followed a zero-order mechanism (n = 0.93). The results of moisture absorption by Karl Fischer has shown the optimum SR pellets at 25°C/60% RH, 30°C/65% RH, and 40°C/75% RH chambers from 1 hr-4 weeks, attributing that the moisture absorption was not significantly increased. In the in vivo study, the results of the bioavailability data showed the T_max (from 0.65 ± 0.082 hr-4.82 ± 2.12 hr) and AUC_{0-30 hr} (from 734.88 ± 230.68 ng/mL.hr-1454.86 ± 319.28 ng/mL.hr) were prolonged and increased, as well as C_max (from 251.87 ± 27.51 ng/mL-115.08 ± 14.87 ng/mL) was decreased for optimum SR-PB pellets when compared with commercial immediate-release (IR) tablets. Furthermore, a good linear regression relationship (r = 0.9943) was observed between the fraction dissolution and fraction absorption for the optimum SR pellets. In this study, the formulation design not only improved the hygroscopic character of PB but also achieved the SR effect.     

Evaluation of topical application of clobetasol 17-propionate from various cream bases

The effect of clobetasol 17-propionate (CP), a potent corticosteroid, in various cream bases on the permeation through artificial membrane was sought. Four formulations were then chosen for a further in vivo skin blanching assay. After calculation of the relationship between in vivo flux_0-8hr determined from a surface recovery technique and in vitro release rate_0-8hr of CP from various formulations, a high correlation coefficient of 0.9996 was achieved. Therefore, the in vitro release study could be used as an index to predict and evaluate the in vivo penetration capacity of CP cream to screen the effective formulation preclinically. After a series of in vivo investigations in this study, it was concluded that myristic acid-added formulations may show a bioequivalence with commercial Dermovate®. Furthermore, the flux calculated from the surface recovery technique and ΔE^* detected from the skin blanching assay may be useful as parameters evaluating the quality and effectiveness of CP cream.     

Bioequivalence evaluation of two formulations of doxazosin tablet in healthy thai male volunteers

The bioequivalence of two doxazosin 2 mg tablets was determined in 24 healthy Thai male volunteers after one single dose in a randomized cross-over study with a one week washout period. The study was conducted at Faculty of Pharmaceutical Sciences and Health Sciences Research Institute, Naresuan University, Phitsanulok, Thailand. Reference (Cardura®, Heinrich Mack Nachf. GmbH & Co. GK, Illertissen, Germany) and test (Dozozin-2®, Umeda Co., Ltd., Bangkok Thailand) were administered to volunteers after overnight fasting. Blood samples were collected at specified time intervals and plasma was separated. The validated HPLC method with fluorescence detection was used for quantification of doxazosin in plasma samples. The pharmacokinetic parameters, T_max, C_max, AUC_t, AUC_∞, T_1/2, λ_z, Cl and V_d, were determined from plasma concentration time profile of both formulations by using non-compartment analysis. The calculated pharmacokinetic parameters were compared statistically to evaluate bioequivalence between the two brands. The analysis of variance (ANOVA) using log-transformed C_max, AUC_t, and AUC_∞ did not show any significant difference between two formulations. The point estimates and 90% confidence intervals for C_max, AUC_t and AUC_∞ were within the acceptance range (0.80-1.25), satisfying the bioequivalence criteria of the Thailand Food and Drug Administration Guidelines. These results indicate that Dozozin-2® is bioequivalent to Cardura® and, thus, may be prescribed interchangeably.     

The in Vitro and in Vivo Performance of a Novel Slow Release Capsule-Compared with a Conventional Capsule

A comparative in vitro and in vivo performance study of a novel slow release capsule (prepared using the new laser drilled controlled drug delivery system) and a conventional capsule dosage from has been made using tetracycline hydrochloride as a model drug. The influence of variation in drug delivery system design on the in vivo performance was studied by urinary excretion rate studies in human volunteers. Slow release capsules released its contents relatively slowly, over a period of time, both in vitro and in vivo, as compared to conventional capsules, with significantly similar K_e and t_1/2 values. Plasma C_max and t_max and AUC values were predicted based on the reported correlation between serum and urinary excretion data in single dose trials.     

Preparation and pharmacokinetics in rabbits of breviscapine unilamellar vesicles

The purpose of the study was to prepare the unilamellar liposomal vesicles of breviscapine (Breviscapine-LUVs) and investigate the pharmacokinetics of Breviscapine-LUVs in rabbits. Breviscapine-LUVs were prepared by the film dispersion method and treated further by extrusion. Its size distribution and zeta potential were determined by photon correlation spectroscopy. The encapsulation efficiency (EE) and cumulative release of Breviscapine-LUVs were assayed by the dialysis method. The crossover design (two periods) was used in six rabbits, which were administered Breviscapine-LUVs and reference preparation. Results showed that the particle size of Breviscapine-LUVs was 50.8 nm, and the polydispersity index was 0.287. The zata potential was -24 mV ± 9 mV(n = 3), and the EE% was 81.1 ± 1.1% (n = 3). The cumulative release of vesicles in 0.9% NaCl was 17.2 ± 0.78%, 26.1 ± 0.68%, and 29.9 ± 0.81% in 2, 8, and 24 h, respectively. The mean concentration-time curves of breviscapine liposomes and reference preparation were both fitted to a two-compartment model with the main pharmacokinetic parameters as follows: t_1/2β of Breviscapine-LUVs and reference preparation were (42.5 ± 28.6) min and (6.01 ± 4.64) min, respectively; CL_(s) were (15.3 ± 9.03) mL × min^-1 and (84.6 ± 40.6) mL × min^-1, respectively; AUC_0-300 were (1267 ± 1083) μg × min × mL^-1 and (196 ± 107) μg × min × mL^-1, respectively. Compared with the reference preparation, breviscapine liposomes had a much higher concentration in plasma and contained characteristic of sustained-release, which ameliorated the pharmacokinetic properties of scutellarin.     

Design and evaluation of matrix diffusion controlled transdermal patches of verapamil hydrochloride

Transdermal patches of verapamil hydrochloride were prepared using four different polymers (individual and combination): Eudragit RL100 (ERL100), Eudragit RS100 (ERS100), hydroxypropyl methylcellulose 15 cps (HPMC), and ethyl cellulose (EC), of varying degrees of hydrophilicity and hydrophobicity. The effect of the polymers on the technological properties, i.e., drug release, water vapor transmission rate (WVTR), and percentage moisture loss (ML), percentage moisture absorption (MA), folding endurance, and thickness, was investigated. Different formulations were prepared in accordance with the 2³ factorial design, with ERL100 being the parent polymer. The patch containing ERL100 alone showed maximum WVTR, % MA, and % ML, which could be attributed to its hydrophilic nature. As expected, substitution with ERS100, HPMC, and EC decreased all the above values in accordance with their decreasing degree of hydrophilicity. In vitro release studies showed zero-order release of the drug from all the patches, and the mechanism of release was diffusion mediated. Moreover, the release of the drug was sustained and it extended over a period of 24 hr in all formulations. A12 emerged as the most satisfactory formulation insofar as its technological properties were concerned. Further, release and permeation of the drug from the most satisfactory formulation (A12) was evaluated through different biological barriers (shed snake skin, rabbit skin, and rat skin) to get an idea of the drug permeation through human skin. Shed snake's skin was found to be most permeable (82.56% drug release at 24 hr) and rat skin was least permeable (52.38%). Percutaneous absorption studies were carried out in rabbits. The pharmacokinetic parameters calculated from blood levels of the drug revealed a profile typical of a sustained release formulation, with the ability to maintain adequate plasma levels for 24 hr. [AUC: 3.09 mg/mL hr, C_max: 203.95 µg/mL, T_max: 8 hr]. It can therefore be concluded that the patch containing ERL100 and HPMC in the ratio 8:2 has achieved the objectives of transdermal drug delivery system, such as avoidance of first pass effect, extended release, and reduced frequency of administration.     

Oral absorption and pharmacokinetics of rebamipide and rebamipide lysinate in rats

Rebamipide is an anti-ulcer agent exhibiting a low aqueous solubility and a poor oral bioavailability. This study was conducted to examine if the rebamipide lysinate salt form would exhibit improved solubility profiles and higher oral bioavailability compared with rebamipide free acid. Both compounds showed pH-dependent solubility profiles, with the solubility of rebamipide lysinate dramatically improved at a median pH of 5.1 (17-fold increases) over free acid, but the improvement in the solubility was not as pronounced in artificial gastric and intestinal fluids (1.4- and 1.9-fold increases, respectively). The Cl, V_ss and t_1/2 in rats after i.v. injection of rebamipide (0.5 mg/kg) averaged 21.0 ± 3.2 ml/min/kg, 0.3 ± 0.0 L/kg, and 0.4 ± 0.1 hr, respectively. No significant difference was observed in these parameters between rebamipide and rebamipide lysinate. Despite improved solubility profiles, the absolute oral bioavailability of rebamipide lysinate was not increased (5.1 vs. 4.8%) nor did AUC (407.8 vs. 383.6 ng^.hr/ml) and C_max (87.4 vs.77.0 ng/ml) compared with rebamipide free acid. Rebamipide lysinate, however, showed a more rapid absorption, and initial serum drug concentrations were higher than those found for rebamipide free acid.     

A Novel Fullerene Hydroxamic Acid for the Liquid-Liquid Extraction, Separation, Preconcentration, and Spectrophotometric and ICP-AES Determination of Vanadium

A new reagent N-phenyl-(1,2 methanofullerene C₆₀)61-formohydroxamic acid (PMFFA) is reported for extraction and trace determination of vanadium(V) in nutritional and biological substrates. The extraction mechanism of vanadium from 6 M HCl media is investigated. The influence of PMFFA, diverse ions, and temperature on the distribution constant of vanadium examined. The over all stability constant (log β₂K_e) and extraction constant (K_ex) are 20.89 ± 0.02 and 8.0 ± 0.02 × 10^-15, respectively in chloroform. The thermodynamics parameters are calculated and kinetics of vanadium transport is discussed. The system obeys Beer's law in the range of 3.2-64.0 ng mL^-1 of vanadium(V). The molar absorptivity is 7.96 × 10⁵ L mol^-1 cm^-1, at 510 nm. The PMFFA-vanadium(V) complex chloroform extract in chloroform was directly inserted into plasma for ICP-AES measurement, which increases the sensitivity by 50 folds and obey Beer's law in the range of 50-1200 pg mL^-1 of vanadium(V). The method is applied for determination vanadium in real standard samples, sea water, and environmental samples.