Development and validation of an in vitro-in vivo correlation for buspirone hydrochloride extended release tablets

D-optimal mixture design inspired modified release tablet formulation of lamotrigine for the treatment of seizures: An in-depth characterization

OBJECTIVE

Lamotrigine (LTG) an anticonvulsant drug with a dissociation constant (pKa: 5.7), suffers from enhanced blood plasma spike after each dose, when administered as fast release tablet. Being BCS class-II candidate and pH dependent solubility, development of release-controlled tablets of LTG is a major challenge. This investigation aims at designing the release-controlled tablet (RCT) formulation of LTG using a solid dispersion (SD) technique via addressing its solubility and release problems.

MATERIAL AND METHODS

RCT of LTG was fabricated using SD blend of Eudragit RL and Eudragit RS and PVP K-30 with different polymer blend ratio (1:5 and 1:7). The optimization of RCT of LTG was performed using D-optimal mixture design with three independent variables, three response variables, and one constraint. The dissolution rate was determined and data were then fitted to different mathematical models. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies and tableting parameters were analyzed.

RESULT

In vitro studies of predicted optimized batches (POBs) have shown that drug release over a period of 12hours was 88.05±3.4% in media I, 86.10±3.7% in media II and 85.84±4.2% in media III. An in vitro kinetic model equating R2-value for all the tested models indicated that the first order and Higuchi release kinetics model were the most appropriate.

CONCLUSION

Based on the optimized formulation consisting of SD of LTG with Eudragit RL, Eudragit RS and PVP K-30, the release rate was consistently similar throughout the GI tract, regardless of the pH of the environment.

Evaluation of in vitro dissolution profiles of modified-release metoprolol succinate tablets crushed using mortar and pestle technique

PURPOSE

Clinical practice guidelines advise against crushing modified-release dosage forms. Metoprolol succinate modified-release (MS-MR) tablets are commonly crushed in clinical practice to facilitate administration to patients with swallowing difficulties or using feeding tubes. To date, the effect of this practice remains unexplored. The in vitro effects of crushing commercially available MS-MR tablets were explored using a holistic approach.

METHODS

Dissolution profiles of crushed versus whole MS-MR tablets were compared. Tablets were crushed to powder state using pragmatic method mimicking hospital practices. For standardization purposes, the same operator, duration (60 seconds), hand, and mortar-pestle apparatus were used. Dissolution studies were conducted per U.S. Pharmacopeia at pH 1.2, pH 4.5, and pH 6.8 with USP apparatus 2 (paddle) at rotation speed of 50 rpm at 37±0.5 °C in 500 mL dissolution media. Samples were withdrawn at predetermined time points. Percent drug dissolved was measured by validated UV-vis Spectrophotometry. Comprehensive analysis of the dissolution data was conducted using model-independent, model-dependent, and ANOVA-based approaches (SPSS v.23 at α=0.05). Similarity (f2) and difference (f1) factors were calculated to compare the dissolution profiles between crushed (CT) and whole tablets (WT). Goodness of fit (GOF) analysis examined the compliance between in vitro dissolution behaviors and several drug release models. Model selection was based on GOF plots, Akaike criteria and adjusted coefficient of determination (R2adj). Imaging and particle size distribution analysis were conducted to examine associated surface and morphologic changes.

RESULTS

The dissolution profiles were not similar at pH 4.5 (f2=45.43, f1=18.97) and pH 6.8 (f2=31.47, f1=32.94). CT best fitted with Higuchi (pH 1.2: R2adj=0.9990), Weibull (pH 4.5: R2adj=0.9884), and Korsmeyer-Peppas (pH 6.8: R2adj=0.9719). Contrastingly, WT best fitted with Hopfenberg (pH 1.2: R2adj=0.9986), logistic (pH 4.5: R2adj=0.9839) and first-order (pH 6.8: R2adj=0.9979) models. A significant difference in the dissolution profiles was found between CT and WT using multivariate analysis of variance per time points and between the tablet forms (p=0.004). This was confirmed by unparalleled dissolution profiles. Crushing resulted in variations in particle size and surface morphological changes to the micropellets.

CONCLUSION

Crushing practices change the dissolution profile of MS-MR tablets by deforming the surface morphology of embedded micropellets. Amounts of drug dissolved between CT and WT were not the same at the compared time points across gastrointestinal pH ranges. This suggests potential clinical impact on plasma-concentration profiles of critically ill patients using feeding tube.

Applications of bio-predictive dissolution tools for the development of solid oral dosage forms: Current industry experience

Development and optimization of orally administered drug products often require bio-predictive tools to help with informing formulation and manufacturing decisions. Reliable bio-predictive dissolution toolkits not only allow rational development of target formulations without having to conduct excessive in vivo studies but also help in detecting critical material attributes (CMAs), critical formulation variables (CFVs), or critical process parameters (CPPs) that could impact a drug's in vivo performance. To provide early insights for scientists on the development of a bio-predictive method for drug product development, this review summarizes current phase-appropriate bio-predictive dissolution approaches applicable to address typical concerns on solubility-limited absorption, food effect, achlorhydria, development of extended-release formulation, clinically relevant specification, and biowaiver. The selection of an in vitro method which can capture the key rate-limiting step(s) of the in vivo dissolution and/or absorption is considered to have a better chance to produce a meaningful in vitro-in vivo correlation (IVIVC) or in vitro-in vivo relationship (IVIVR).

Response Surface Methodology for Optimization of Buspirone Hydrochloride-Loaded In Situ Gel for Pediatric Anxiety

The purpose of the current investigation was to formulate, assess, and optimize oral in situ gels of buspirone hydrochloride (BH) with the specific end goal of expanding the time the medication spends in the stomach, thereby ensuring an extended medication discharge. This would allow the use of a once-a-day dose of liquid BH formulations, which is ideal for the treatment of pediatric anxiety. In situ gels loaded with BH were prepared using various concentrations of sodium alginate (Na alg.), calcium chloride (CaCl₂), and hydroxypropyl methylcellulose (HPMC K15M). The in situ gels exhibited the desired consistency, drug distribution, pH, ability to form gel, and prolonged drug release in vitro. The (3³) full factorial design was utilized for the revealing of the ideal figures for the selected independent variables, Na alg. (X₁), HPMC (X₂), and CaCl₂ (X₃) based on measurements of the viscosity (Y₁) and percentage drug release after 6 h (Y₂). A pharmacokinetic study of the optimum formulation on rabbits was also performed. The formulation containing 2% of Na alg., 0.9% of HPMC-K15M, and 0.1125% of CaCl₂ was selected as the ideal formulation, which gave the theoretical values of 269.2 cP and 44.9% for viscosity and percentage of drug released after 6 h, respectively. The pharmacokinetic study showed that the selected oral Na alg. in situ gel formulation displayed a prolonged release effect compared to BH solution and the marketed tablet (Buspar^®), which was confirmed by the low C_max and high T_max values. The optimum oral Na alg. in situ gel showed a 1.5-fold increment in bioavailability compared with the drug solution.

Formulation and bioequivalence studies of choline alfoscerate tablet comparing with soft gelatin capsule in healthy male volunteers

Purpose

The aim of this study was to develop a tablet formulation of choline alfoscerate and to assess its bioequivalence by comparing its pharmacokinetic parameters with those of a commercially available soft gelatin capsule (Gliatilin^®) in healthy Korean male volunteers.

Materials and methods

Film-coated tablet formulation was optimized to control the hygroscopicity of choline alfoscerate. Bioequivalence study was performed under fasted condition with a randomized, single-dose, two-period crossover design. Subjects were orally treated with 1,200 mg of test or reference choline alfoscerate (400 mg × three doses) formulation. Blood samples were collected up to 12 hours the day before dosing to correct the baseline level of choline and 12 hours after dosing to obtain drug absorption profile. Pharmacokinetic parameters were determined after analyzing plasma concentration of choline by using LC–MS/MS.

Results

Hygroscopicity of choline alfoscerate was successfully controlled by adding suitable amount of Neusilin^® (magnesium aluminometasilicate) in the film-coated tablet. Stability of the tablet formulation was also confirmed under the accelerated condition for 3 months. Bioequivalence study showed that the mean area under the plasma concentration–time curve from time 0 to infinity of test tablet and reference soft capsule was 3.428±2.170 and 3.305±1.803 µg⋅h/mL, respectively; the mean C_max was 0.365±0.158 and 0.380±0.108 µg/mL, respectively; and the mean T_max was 3.51±2.57 and 3.85±3.19 hours, respectively. The 90% CIs for geometric mean ratios of test to reference formulation for AUC_0–t and C_max were 84.51%–111.98% and 83.31%–104.10%, respectively, and satisfied the EMA regulatory criteria for bioequivalence.

Conclusion

Pharmacokinetic parameters including the C_max and AUC_0–t determined after oral administration of the two formulations in healthy Korean male volunteers showed that the differences between the formulations (tablet vs soft capsule) were not significant for bioequivalence. Both formulations were well tolerated, with no serious adverse events reported.

Development, Internal and External Validation of Naproxen Sodium Sustained Release Formulation: an Level A In Vitro-In Vivo Correlation

Objectives

The aim of the present study was to develop and validate an in vitro-in vivo correlation (IVIVC) for naproxen sodium-sustained release tablets and to compare their plasma concentrations over time with the immediate-release tablets.

Materials and Methods

In vitro release rate data were obtained for each tablet by using the USP Apparatus II, paddle stirrer at 50 rpm in pH 7.4 phosphate buffer. A four-way crossover study was conducted in 6 healthy subjects by administering naproxen sodium sustained release 375 mg and 500 mg of immediate release tablets. Series of blood samples were collected over 24 hours and estimated by using the validated liquid chromatography tandem-mass spectrometry method.

Results

The similarity factor was calculated and it was found that values between, 50 and 100 indicates similarity of the profiles. Assessment of predicted and observed bioavailability was performed and prediction errors (PE) % calculated, as per the Food Drug Administration guidelines, the average absolute PE% of C_max and AUC of individual formulation was found below 15% for establishment of IVIVC, based on internal prediction strongly suggesting that the naproxen sodium IVIVC models are valid. During external validation the predicted curve for the naproxen sodium sustained-release tablets was found to be identical to immediate release tablets and considered as valid.

Conclusion

IVIVC can serve as a surrogate for in vivo bioavailability study and supports biowaivers, supports and validates the dissolution methods and specification settings and assists in quality control during scale-up and post-approval changes. It may be used to predict the variation in site change, process changes and to predict the absorption performance of naproxen sodium products with different release rates.

Dissolution method for delapril and manidipine combination tablets based on an absorption profile of manidipine

The present study describes the development and validation of a dissolution method for delapril (DEL) and manidipine (MAN) combination tablets, using a simulated absorption profile based on in vivo data for MAN. The suitable in vitro dissolution profile for this formulation was obtained using 900 mL of citrate buffer pH 3.2 at 37 °C±0.5 °C as dissolution medium and USP apparatus 2 (paddle) at 75 rpm. All samples were analyzed by a liquid chromatography (LC) method. Under these conditions, a significant linear relationship between the absorbed (calculated by deconvolution approach) and dissolved fractions of MAN was obtained (R=0.997) and an in vivo-in vitro (IVIV) correlation for this particular formulation containing MAN can be established. Validation parameters for dissolution methodology such as the specificity, linearity, accuracy and precision were also evaluated according to the international guidelines, giving results within the acceptable range. Therefore, the proposed dissolution conditions can be applied for the simultaneous release analysis of DEL and MAN from the solid dosage form, contributing to the improvement of the quality control of pharmaceutics and minimizing the number of bioavailability studies.

Provesicular granisetron hydrochloride buccal formulations: in vitro evaluation and preliminary investigation of in vivo performance

Granisetron hydrochloride (granisetron) is a potent antiemetic that has been proven to be effective in acute and delayed emesis in cancer chemotherapy. Granisetron suffers from reduced oral bioavailability (≈60%) due to hepatic metabolism. In this study the combined advantage of provesicular carriers and buccal drug delivery has been explored aiming to sustain effect and improve bioavailability of granisetron via development of granisetron provesicular buccoadhesive tablets with suitable quality characteristics (hardness, drug content, in vitro release pattern, exvivo bioadhesion and in vivo bioadhesion behavior). Composition of the reconstituted niosomes from different prepared provesicular carriers regarding type of surfactant used and cholesterol concentration significantly affected both entrapment efficiency (%EE) and vesicle size. Span 80 proniosome-derived niosomes exhibited higher encapsulation efficiency and smaller particle size than those derived from span 20. Also, the effect of %EE and bioadhesive polymer type on in vitro drug release and in vivo performance of buccoadhesive tablets was investigated. Based on achievement of required in vitro release pattern (20-30% at 2h, 40-65% at 6h and 80-95% at 12h), in vivo swelling behavior, and in vivo adhesion time (>14 h) granisetron formulation (F19, 1.4 mg) comprising HPMC:carbopol 974P (7:3) and maltodextrin coated with the vesicular precursors span 80 and cholesterol (9:1) was chosen for in vivo study. In vivo pharmacokinetic study revealed higher bioavailability of buccal formulation relative to conventional oral formulation of granisetron (AUC0-∞ is 89.97 and 38.18 ng h/ml for buccal and oral formulation, respectively). A significantly lower and delayed Cmax (12.09±4.47 ng/ml, at 8h) was observed after buccal application compared to conventional oral tablet (31.66±10.15 ng/ml, at 0.5 h). The prepared provesicular buccoadhesive tablet of granisetron (F19) might help bypass hepatic first-pass metabolism and improve bioavailability of granisetron with the possibility of reducing reported daily dose (2mg) and reducing dosing frequency.

Gemifloxacin mesylate (GFM): dissolution test based on in vivo data

Gemifloxacin mesylate (GFM) is a synthetic, broad-spectrum, fluoroquinolone antibacterial agent. It is different from other class members because it achieves adequate plasma concentrations to inhibit both topoisomerase IV and gyrase. The aim of this study was to develop and validate a dissolution test for GFM in coated tablets, using a simulated absorption profile based on in vivo data obtained from the literature. The fraction and percentage of the dose absorbed were calculated using model-dependent Loo-Riegelman approach for two compartments. The best in vitro dissolution profile was obtained using 900 mL of pH 6.0 phosphate buffer as a dissolution medium at 37 °C ± 0.5 °C and paddles at 50 rpm. The in vitro dissolution samples were analyzed using a liquid chromatography method, and the validation was performed according to USP 34 (2011). The method showed specificity, precision, accuracy, robustness and linearity. Under these conditions, a level-A in vitro-in vivo correlation was suggested (r = 0.9926). The prediction errors were calculated to determine the validity and accuracy of the suggested correlation. The dissolution test can be used to evaluate the dissolution profile of GFM-coated tablets and minimize the number of bioavailability studies as part of new formulation development.

Preparation and in vitro/in vivo evaluation of microparticle formulations containing meloxicam

In this study, we have formulated chitosan-coated sodium alginate microparticles containing meloxicam (MLX) and aimed to investigate the correlation between in vitro release and in vivo absorbed percentages of meloxicam. The microparticle formulations were prepared by orifice ionic gelation method with two different sodium alginate concentrations, as 1% and 2% (w/v), in order to provide different release rates. Additionally, an oral solution containing 15 mg of meloxicam was administered as the reference solution for evaluation of in vitro/in vivo correlation (ivivc). Following in vitro characterization, plasma levels of MLX and pharmacokinetic parameters [elimination half-life (t(1/2)), maximum plasma concentration (C(max)), time for C(max) (t(max))] after oral administration to New Zealand rabbits were determined. Area under plasma concentration-time curve (AUC(0-∞)) was calculated by using trapezoidal method. A linear regression was investigated between released% (in vitro) and absorbed% (in vivo) with a model-independent deconvolution approach. As a result, increase in sodium alginate content lengthened in vitro release time and in vivo t(max) value. In addition, for ivivc, linear regression equations with r(2) values of 0.8563 and 0.9402 were obtained for microparticles containing 1% and 2% (w/v) sodium alginate, respectively. Lower prediction error for 2% sodium alginate formulations (7.419 ± 4.068) compared to 1% sodium alginate formulations (9.458 ± 5.106) indicated a more precise ivivc for 2% sodium alginate formulation.

Improved bioavailability of poorly water-soluble drug curcumin in cellulose acetate solid dispersion

Curcumin (Cur), one of the most widely used natural active constituents with a great variety of beneficial biological and pharmacological activities, is a practically water-insoluble substance with a short biologic half-life. The aim of this study was to develop a sustained-release solid dispersion by employing water-insoluble carrier cellulose acetate for solubility enhancement, release control, and oral bioavailability improvement of Cur. Solid dispersions were characterized by solubility, in vitro drug release, Fourier transform infrared spectroscopy, X-ray diffractometry, and differential scanning calorimetry studies. The in vivo performance was assessed by a pharmacokinetic study. Solid-state characterization techniques revealed the amorphous nature of Cur in solid dispersions. Solubility/dissolution of Cur was enhanced in the formulations in comparison with pure drug. Sustained-release profiles of Cur from the solid dispersions were ideally controlled in vitro up to 12 h. The optimized formulation provided an improved pharmacokinetic parameter (C(max) = 187.03 ng/ml, t(max) = 1.95 h) in rats as compared with pure drug (C(max) = 87.06 ng/ml, t(max) = 0.66 h). The information from this study suggests that the developed solid dispersions successfully enhanced the solubility and sustained release of poorly water-soluble drug Cur, thus improving its oral bioavailability effectively.

Formulation and optimization of solid lipid nanoparticles of buspirone HCl for enhancement of its oral bioavailability

Solid lipid nanoparticles (SLNs) of buspirone HCl as a water-soluble drug were prepared by emulsification-evaporation, followed by the sonification method. A preliminary screening of the most effective parameters on the production of nanoparticles by a Taguchi L(8) orthogonal array showed that the lipid type, surfactant percentage, speed of homogenizer, and acetone:dichloromethane (DCM) ratio had a significant effect on particle size. In the next step, the lipid was fixed on cetyl alcohol, surfactant on Tween 20, lecithin:lipid weight ratio on 20:70, sonication time on 30 seconds, and the other effective, independent factors aforementioned were studied each at three levels by a three-factor, three-level Box-Behnken design. The percentage of drug entrapment, mean particle-size diameter, and zeta potential were studied as the responses. Contour plots were constructed to further elucidate the relationship between the independent and dependent variables. A pharmacokinetic study was conducted in male Wistar rats after oral administration of 15 mg.kg(-1) buspirone in the form of free drug or SLNs. The optimized SLNs had aq particle size of 345.7 nm, loading efficiency of 32.8%, and zeta potential of -6.8 mV. Buspirone released about 90% during 4.5 hours in vitro. It was found that the relative bioavailability of the drug in SLNs was significantly increased, compared to that of the drug solution.

Application of biorelevant dissolution tests to the prediction of in vivo performance of diclofenac sodium from an oral modified-release pellet dosage form

In vitro biorelevant dissolution tests enabling the prediction of in vivo performance of an oral modified-release (MR) dosage form were developed in this study. In vitro dissolution of MR diclofenac sodium pellets containing 100mg active ingredient was evaluated under simulated pre- and postprandial conditions using USP Apparatus 3 (reciprocating cylinder, Bio-Dis) and 4 (flow-through cell) and results compared with compendial methods using USP Apparatus 1 (basket) and 2 (paddle). In vivo, the effects of food on the absorption of diclofenac sodium from the pellet dosage form were investigated by administering the product to 16 healthy volunteers pre- and postprandially in a crossover-design study. The in vitro results were compared with the in vivo data by means of Level A in vitro-in vivo correlation (IVIVC) and Weibull distribution analysis. The compendial dissolution tests were not able to predict food effects. The biorelevant dissolution tests predicted correctly that the release (and hence absorption) of diclofenac sodium would be slower in the fed state than in the fasted state. No significant differences in extent of absorption due to changes in extent of release were predicted or observed. The results demonstrate good correlations between in vitro drug release and in vivo drug absorption in both pre- and postprandial states using the biorelevant dissolution test methods.

The science of USP 1 and 2 dissolution: present challenges and future relevance

Since its inception, the dissolution test has come under increasing levels of scrutiny regarding its relevance, especially to the correlation of results to levels of drug in blood. The technique is discussed, limited to solid oral dosage forms, beginning with the scientific origins of the dissolution test, followed by a discussion of the roles of dissolution in product development, consistent batch manufacture (QC release), and stability testing. The ultimate role of dissolution testing, "to have the results correlated to in vivo results or in vivo in vitro correlation," is reviewed. The recent debate on mechanical calibration versus performance testing using USP calibrator tablets is presented, followed by a discussion of variability and hydrodynamics of USP Apparatus 1 and Apparatus 2. Finally, the future of dissolution testing is discussed in terms of new initiatives in the industry such as quality by design (QbD), process analytical technology (PAT), and design of experiments (DOE).

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 2(3) full factorial design. In vitro studies, the 2(3) 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 degrees C/60% RH, 30 degrees C/65% RH, and 40 degrees 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 Tmax (from 0.65+/-0.082 hr-4.82+/-2.12 hr) and AUC0-30 hr (from 734.88+/-230.68 ng/mL.hr-1454.86+/-319.28 ng/mL.hr) were prolonged and increased, as well as Cmax (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.

Formulation design of an HPMC-based sustained release tablet for pyridostigmine bromide as a highly hygroscopic model drug and its in vivo/in vitro dissolution properties

Pyridostigmine bromide (PB), a highly hygroscopic drug was selected as the model drug. A sustained-release (SR) tablet prepared by direct compression of wet-extruded and spheronized core pellets with HPMC excipients and exhibited a zero-order sustained release (SR) profile. The 2(3) full factorial design was utilized to search an optimal SR tablet formulation. This optimal formulation was followed zero-order mechanism and had specific release rate at different time intervals (released % of 1, 6, and 12 hr were 15.84, 58.56, and 93.10%). The results of moisture absorption by Karl Fischer meter showed the optimum SR tablet could improve the hygroscopic defect of the pure drug (PB). In the in vivo study, the results of the bioavailability data showed the T(max) was prolonged (from 0.65 +/- 0.082 hr to 4.83 +/- 1.60 hr) and AUC(0-t) (from 734.88 +/- 230.68 ng/ml.hr to 1153.34 +/- 488.08 ng/ml.hr) and was increased respectively for optimum PB-SR tablets when compared with commercial immediate release (IR) tablets. Furthermore, the percentages of in vitro dissolution and in vivo absorption in the rabbits have good correlation. We believe that PB-SR tablets designed in our study would improve defects of PB, decrease the frequency of administration and enhance the retention period of drug efficacy in vivo for personnel exposed to contamination situations in war or terrorist attacks in the future.

Predicting Human Drug Pharmacokinetics from In Vitro Permeability Using an Absorption–Disposition Model

The purpose of this research is to simulate the in vivo performance of drugs with a wide range of solubility and permeability characteristics formulated as oral dosage forms. The absorption-disposition model was developed using a number of physiological parameters as well as in vitro permeability data generated with Caco-2 cells, 2/4/A1 cells, and hexadecane membranes. A total of 13 drugs with varying solubility and permeability properties were examined using the absorption-disposition model to predict their pharmacokinetic profile. The correlation of predicted and experimentally determined AUC and Cmax, as measures of the pharmacokinetic profile, were >0.96 for all permeation techniques examined. The predictive ability of the model is influenced by the type of permeation method employed; 2/4/A1 cell data yielded the highest degree of accuracy in predicting Cmax and AUC values. The absorption-disposition model developed in this work accurately predicts the in vivo performance of a wide range of orally administered drugs with 8 of 9 drugs examined falling within 80-125% of the experimental value of AUC when using 2/4/A1 cells.

An investigation of acetylcholine released in skeletal muscle and protein unbound drug released in blood based on the pyridostigmine bromide (pretreatment drug) sustained-release pellets by microdialysis technique in the rabbit model

Pyridostigmine bromide (PB) is a reversible acetylcholinesterase inhibitor that has been used as a pretreatment drug for "Soman" nerve gas poisoning in combat to increase survival. The once-daily PB-sustained-release (SR) pellets were developed by extrusion-spheronization and fluid-bed methods in our laboratory, which was followed by zero-order release mechanism. The results showed that the released concentration of acetylcholine (ACh) in skeletal muscle and the released concentration of protein unbound drug in blood were determined by microdialysis technique to have significant differences (P<0.05) among the three dosage forms (IV injection, commercial IR tablets and the PB-SR pellet). The released concentrations of ACh and protein unbound drug for PB-SR pellets were slower than IV injection and commercial IR tablets; this phenomenon indicating that the retention period of drug efficacy in vivo for PB-SR pellet was longer than the others, that is to say, the PB-SR pellets provided with SR effect in vivo as well. We believe that once-daily administered PB-SR pellets would improve limitations of post-exposure antidotes, decrease the frequency of administration and enhance the retention period of drug efficacy in vivo for personnel exposed to contamination situations in wars or terrorist attacks in the future.

Studies on controlled release effervescent osmotic pump tablets from Traditional Chinese Medicine Compound Recipe

A controlled release effervescent osmotic pump tablet (EOPT) of Traditional Chinese Medicine Compound Recipe (TCMCR), named Fuzilizhong prescription which includes acidic drugs consisted of many known and unknown effective components and has been used for several thousands years, was successfully prepared with sodium chloride, sodium hydrogen carbonate and hydroxypropylmethylcellulose(HPMC) as osmotic agents. Since the osmotic pressure in EOPT with sodium chloride and sodium hydrogen carbonate increased greatly, which was induced mostly by gas carbon dioxide generating from the reaction of sodium hydrogen carbonate and the acidic drugs in TCMCR after the fluid being imbibed into the compartment through the semipermeable membrane and the in vitro accumulative dissolution percent from prescription 3 was up to 96.6% at 14 hour, the problem that water insoluble drugs can not to be elementary osmotic pump tablet for its low dissolution rate was solved in the paper. On the basis of prescription 3, the drug in effervescent osmotic pump tablet was released controllably after HPMC was selected as retarder and has a good in-vitro-in-vivo correlation(IVIVC, r=0.9550). Threrfore, it could be concluded that the formulation of TCMCR is appropriate to being made into EOPT, which improves acidic drugs composed of soluble and poorly soluble components release more greatly and controllably. From the point of this, water insoluble drugs can be designed to elementary osmotic pump tablet for more complete dissolution release.

Improving of the accuracy of in vitro-in vivo linear correlation using kinetic models for ultra sustained release theophylline tablets

The objective of the current study was to establish and evaluate a new technique to increase the accuracy of the in vitro/in vivo linear correlation of single and multiple dose ultra-sustained release theophylline (USRT) preparation (Xantium) in hospitalized patients. In vitro dissolution data for theophylline were collected for 24 h using a USP I (basket) and USP II (paddle) methods. In vivo plasma concentration data were obtained from 8 patients after administration of either single or multiple doses of theophylline. Both in vitro and in vivo results were evaluated by zero-order, first-order, RRSBW, Hixson-Crowell, Higuchi, Hopfenberg, Langenbucher, modified Langenbucher and (Bt)a kinetic models. The individual linear correlations between each in vitro and in vivo percent results and their kinetic distributions were established and regression equations were obtained. The determination coefficient results of the linear kinetic correlations were found to be 0.994 and 0.997 for single and multiple doses by basket method and 0.992 and 0.998 for single and multiple doses by paddle method, respectively. Furthermore, the results of the linear correlations were found as 0.953 and 0.950 for single and multiple doses by basket method and 0.963 and 0.962 for single and multiple doses by paddle method respectively. Therefore, this study suggested that the accuracy of the linear correlation could be improved signilicantly by using linear kinetic correlation.