Correlation of "in vitro" release and "in vivo" absorption characteristics of rifampicin from ethylcellulose coated nonpareil beads

Superhydrophobic Surface for Enhancing the Bioavailability of Salbutamol Sulfate from Cross-Linked Microspheres: Formulation, Characterization, and in vivo Evaluation

Introduction

The aim of the work was to formulate salbutamol sulfate (SB) microspheres by using superhydrophobic surface (SHS) under different processing factors for improving its encapsulation efficiency, controling its release rate, and hence enhancing its bioavailability.

Methods

Cross-linked microspheres of chitosan (CN) and carrageenan (KN) were made on a SHS under a glutaraldehyde-saturated atmosphere. The formulations were designed and optimized based on 4² factorial design. Percentage encapsulation efficiency (%EE), particle size, swelling ratio, and in vitro release rate were characterized, and the in vivo performance of optimized formula was investigated in beagle dogs.

Results

The results showed that the prepared microspheres have a high %EE (97.11±0.78%) for F13. The swelling ratio was 4.2 at the end of the 8 hours for the optimized formula, and the in vitro release rate was controlled for 12 hours. In vivo study verified that there was a 1.61-fold enhancement in SB bioavailability from optimized formula (F13) compared to market tablet.

Conclusion

The study suggested that microspheres prepared from CN/KN crosslinking on an SHS using glutaraldehyde atmosphere is a promising technique that can encapsulate and sustain the release of water-soluble drugs such as SB in addition to improving its in vivo pharmacokinetic profile.

Estimation of the In Vivo Release of Amiodarone From the Pharmacokinetics of Its Active Metabolite and Correlation With Its In Vitro Release

Due to its very low water solubility and complex pharmacokinetics, a reliable point-to-point correlation of its in vitro release with its pharmacokinetics has not been achieved so far with amiodarone. The correlation of the in vitro dissolution of a drug with the pharmacokinetics of one of its metabolites was recently proposed by the authors of the article as an additional or alternative analysis to the usual in vitro correlations in vivo, mainly in the case of fast-absorbing drugs that have metabolites with a significant therapeutic effect. The model proposed by the authors considers that amiodarone has a slow dissolution, rapid absorption, and rapid metabolism, and before returning to the blood from other compartments, its pharmacokinetics is determined mainly by the kinetics of release in the intestine from the pharmaceutical formulation. Under these conditions, the rate of apparition of desethylamiodarone in the blood is a metric of the release of amiodarone in the intestinal fluid. Furthermore, it has been shown that such an estimated in vivo dissolution is similar, after time scaling, to the dissolution measured experimentally in vitro. Dissolution data of amiodarone and the pharmacokinetic data of its active metabolite desethylamiodarone were obtained in a bioequivalence study of 24 healthy volunteers. The elimination constant of the metabolite from plasma was estimated as the slope of the linear regression of logarithmically transformed data on the tail of plasma levels. Because the elimination of desethylamiodarone was shown to follow a monoexponential model, a Nelson–Wagner-type mass equilibrium model could be applied to calculate the time course of the “plasma metabolite fraction.” After Levi-type time scaling for imposing the in vitro–in vivo correlation, the problem became that of the correlation between in vitro dissolution time and in vivo dissolution time, which was proven to follow a square root model. To validate the model, evaluations were performed for the reference drug and test drug separately. In both cases, the scaled time for in vivo dissolution, t*, depended approximately linearly on the square root of the in vitro dissolution time t, with the two regression lines being practically parallel.

The Evaluation of Valsartan Biopharmaceutics Properties

BACKGROUND

Solubility, intestinal permeability and dissolution are the main factors that govern the rate and extent of drugs absorption and are directly related to bioavailability. Biopharmaceutics Classification System (BCS) is an important tool which uses in vitro results for comparison with bioavailability in vivo (biowaiver). Valsartan is widely used in the treatment of hypertension and shows different BCS classification in the literature (BCS class II or III).

OBJECTIVE

This work proposes the study of valsartan biopharmaceutics properties and its BCS classification.

METHODS

High Performance Liquid Chromatography (HPLC) method was developed and validated to quantify the drug in buffers pH 1.2, 4.5 and 6.8 respectively. Valsartan solubility was determined in these three different media using shake flask method and intrinsic dissolution rate. Evaluation of dissolution profile from coated tablets was conducted.

RESULTS

The low solubility (pH 1.2 and 4.5) and high solubility (pH 6.8) were observed for both solubility methods. Permeability data reported from the literature showed that valsartan is a low permeability drug. Valsartan presented the rapid release profile only in pH 6.8.

CONCLUSION

We defined that valsartan is a class IV drug, in disagreement with what has been published so far. It is important to emphasize that the conditions considered here are indicated to define the biopharmaceutics classification by regulatory agencies.

In Vitro-In Vivo Correlations Based on In Vitro Dissolution of Parent Drug Diltiazem and Pharmacokinetics of its Metabolite

In this study a novel type of in vitro-in vivo correlation (IVIVC) is proposed: The correlation of the in vitro parent drug dissolution data with the in vivo pharmacokinetic data of drug's metabolite after the oral administration of the parent drug. The pharmacokinetic data for the parent drug diltiazem (DTZ) and its desacetyl diltiazem metabolite (DTZM) were obtained from an in vivo study performed in 19 healthy volunteers. The pharmacokinetics of the parent drug and its metabolite followed a pseudomono-compartmental model and deconvolution of the DTZ or DTZM plasma concentration profiles was performed with a Wagner-Nelson-type equation. The calculated in vivo absorption fractions were correlated with the in vitro DTZ dissolution data obtained with USP 2 apparatus. A linear IVIVC was obtained for both DTZ and DTZM, with a better correlation observed for the case of the metabolite. This type of correlation of the in vitro data of the parent compound with the in vivo data of the metabolite could be useful for the development of drugs with active metabolites and prodrugs.

Superhydrophobic Substrates for Ultrahigh Encapsulation of Hydrophilic Drug into Controlled-Release Polyelectrolyte Complex Beads: Statistical Optimization and In Vivo Evaluation

: In this work, ultrahigh drug-loaded chitosan (Ch)/K-carrageenan (Kc) polyelectrolyte complex (PEC) beads were formed in situ by cross-linking in a glutaraldehyde-saturated atmosphere and were prepared on superhydrophobic substrates fabricated by spraying glass surfaces with ready-made spray for domestic use (NeverWet^®). Verapamil hydrochloride (VP), a highly hydrophilic drug with a short biological half-life, was incorporated into a series of Ch-based and/or Ch/Kc-PEC-based beads to control its release profile in vivo. The formulation of VP-loaded beads was optimized using stepwise statistical designs based on a prespecified criterion. Several characteristics of the prepared beads, such as entrapment efficiency (EE%), in vitro drug release, swelling ratio, size and surface microstructure as well as molecular interactions between the drug and formulation ingredients, were investigated. In vivo pharmacokinetic (PK) studies were carried out using the rabbit model to study the ability of the optimized VP-loaded beads to control the absorption rate of VP. Results revealed that the prepared superhydrophobic substrates were able to fabricate VP-loaded beads with extremely high EE exceeding 90% w/w compared to only 27.80% when using conventional ionotropic gelation technique. PK results showed that the rate of VP absorption was well controlled following oral administration of the optimized beads to six rabbits compared to a marketed VP immediate release (IR) tablet, as evidenced by a 2.2-fold increase in mean residence time (MRT) and 5.24-fold extension in half value duration (HVD) over the marketed product without any observed reduction in the relative oral bioavailability.

Ultrahigh verapamil-loaded controlled release polymeric beads using superamphiphobic substrate: D-optimal statistical design, in vitro and in vivo performance

Controlled-release multiparticulate systems of hydrophilic drugs usually suffer from poor encapsulation and rapid-release rate. In the present study, ultra-high loaded controlled release polymeric beads containing verapamil hydrochloride (VP) as hydrophilic model drug were efficiently prepared using superamphiphobic substrates aiming to improve patient compliance by reducing dosing frequency. Superamphiphobic substrates were fabricated using clean aluminum sheets etched with ammonia solution and were treated with 1.5% (w/v) perfluorodecyltriethoxysilane (PFDTS) alcoholic solution. The effect of the main polymer type (lactide/glycolide (PLGA) 5004A, PLGA 5010, and polycaprolactone (PCL)), copolymer (Eudragit RS100) content together with the effect of drug load on encapsulation efficiency (EE%) and in vitro drug release was statistically studied and optimized via D-optimal statistical design. In vivo pharmacokinetic study was carried out to compare the optimized system relative to the market product (Isoptin®). Results revealed that superamphiphobic substrates were successfully prepared showing a rough micro-sized hierarchical structured surface upon observing with scanning electron microscope and were confirmed by high contact angles of 151.60 ± 2.42 and 142.80°±05.23° for water and olive oil, respectively. The fabricated VP-loaded beads showed extremely high encapsulation efficiency exceeding 92.31% w/w. All the prepared systems exhibited a controlled release behavior with Q12 h ranging between 5.46 and 95.90%w/w. The optimized VP-loaded system composed of 150 mg (1.5% w/v) PCL without Eudragit RS100 together with 160 mg VP showed 2.7-folds mean residence time compared to the market product allowing once daily administration instead of three times per day.

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.

In vitro-in vivo correlation of modified release dosage form of lamotrigine

The plasma concentration profile of lamotrigine was predicted from the dissolution test data of the modified release 100 mg lamotrigine tablet by applying the in vitro-in vivo correlation (IVIVC). Three different release formulations (L-1, L-2 and L-3) and its profiles of in vitro data were generated in different dissolution media. Pharmacokinetics evaluation of these formulations was carried out in 12 healthy volunteers. In vitro-in vivo correlation was established from the generated dissolution and bioavailability data. A good correlation between the percentages dissolved vs absorbed (r2>0.989) was obtained using level A correlation. Evaluation of the internal predictability of level A correlation was calculated in terms of percent prediction error, which was found to be below 15%.

Archaeal tetraether bipolar lipids: Structures, functions and applications

Archaea have developed specific tools permitting life under harsh conditions and archaeal lipids are one of these tools. This microreview describes the particular features of tetraether-type archaeal lipids and their potential applications in biotechnology. Natural and synthetic tetraether lipid structures as well as their applications in drug/gene delivery, vaccines and proteoliposomes or as lipid films are reviewed.