PEGylated liposomes of anastrozole for long-term treatment of breast cancer: in vitro and in vivo evaluation.

The aim of present study was to develop conventional and PEGylated (long circulating), liposomes containing anastrozole (ANS) for effective treatment of breast cancer. ANS is a third-generation non-steroidal aromatase inhibitor of the triazole class used for the treatment of advanced and late-stage breast cancer in post-menopausal women. Under such disease conditions the median duration of therapy should be prolonged until tumor regression ends (>31 months). Liposomes were prepared by the thin film hydration method by using ANS and various lipids such as soyaphosphatidyl choline, cholesterol and methoxy polyethylene glycol distearoyl ethanolamine in different concentration ratios and evaluated for physical characteristics, in vitro drug release and stability. Optimized formulations of liposome were studied for in vitro cytotoxic activity against the BT-549 and MCF-7 cell lines and in vivo behavior in Wistar rats. Preformulation studies, both Fourier transform infrared study and differential scanning calorimetry analysis showed no interaction between the drug and the excipients used in the formulations. The optimized formulations AL-07 and AL-09 liposomes showed encapsulation efficiencies in the range 65.12 ± 1.05% to 69.85 ± 3.2% with desired mean particle size distribution of 101.1 ± 5.9 and 120.2 ± 2.8 nm and zeta potentials of -43.7 ± 4.7 and -62.9 ± 3.5 mV. All the optimized formulations followed Higuchi-matrix release kinetics and when plotted in accordance with the Korsemeyer-Peppas method, the n-value 0.5 < n < 1.0 suggests an anomalous (non-Fickian) transport. Likewise, the PEGylated liposomes showed greater tumor growth inhibition on BT-549 and MCF-7 cell lines from in vitro cytotoxicity studies (p < 0.05). Pharmacokinetic study of conventional and PEGylated liposomes in Wistar rats demonstrated a 3.33- and 20.28-fold increase in AUC(0-∞) values when compared to pure drug (p < 0.001). Among the formulations, PEGylated liposomes showed encouraging results by way of their long circulation and sustained delivery properties for effective treatment of breast cancer.

Development and validation of a HPLC method for quantification of rivastigmine in rat urine and identification of a novel metabolite in urine by LC-MS/MS.

A sensitive, specific and accurate HPLC method for the quantification of rivastigmine (RSM) in rat urine was developed and validated. The method involves the simple liquid-liquid extraction of RSM and pyridostigmine as an internal standard (IS) from rat urine with tertiary methyl butyl ether. The chromatographic separation of RSM and IS was achieved with 20 mm ammonium acetate buffer (pH 6.5) and acetonitrile (65:35, v/v) delivered at flow-rate of 1 mL/min on a Kromasil KR-100. The method was in linear range from 50 to 5000 ng/mL. The validation was done as per FDA guidelines and the results met the acceptance criteria. The method was successfully applied for the quantification of RSM in rat urine. Besides method validation, we have identified two metabolites of RSM in urine. Both the metabolites were characterized by HPLC-PDA and LC-MS/MS and it was found that one metabolite is novel.

Sustained release optimized formulation of anastrozole-loaded chitosan microspheres: in vitro and in vivo evaluation.

The purpose of this study was to develop sustained release formulation of anastrozole-loaded chitosan microspheres for treatment of breast cancer. Chitosan microspheres cross-linked with two different cross-linking agents viz, tripolyphosphate (TPP) and glutaraldehyde (GA) were prepared using single emulsion (w/o) method. A reverse phase HPLC method was developed and used for quantification of drug in microspheres and rat plasma. Influence of cross-linking agents on the properties of chitosan microspheres was extensively investigated. Formulations were characterized for encapsulation efficiency (EE), compatibility of drug with excipients, particle size, surface morphology, swelling capacity, erosion and drug release profile in phosphate buffer pH 7.4. EE varied from 30.4 ± 1.2 to 69.2 ± 3.2% and mean particle size distribution ranged from 72.5 ± 0.5 to 157.9 ± 1.5 µm. SEM analysis revealed smooth and spherical nature of microspheres. TPP microspheres exhibited higher swelling capacity, percentage erosion and drug release compared to GA microspheres. Release of anastrozole (ANS) was rapid up to 4 h followed by slow release status. FTIR analysis revealed no chemical interaction between drug and polymer. DSC analysis indicated ANS trapped in the microspheres existed in amorphous form in polymer matrix. The highest correlation coefficients (R (2)) were obtained for Higuchi model, suggesting a diffusion controlled mechanism. There was significant difference in the pharmacokinetic parameters (AUC(0-∞), Kel and t(1/2)) when ANS was formulated in the form of microspheres compared to pure drug. This may be attributed to slow release rate of ANS from chitosan microspheres and was detectable in rat plasma up to 48 h which correlates well with the in vitro release data.

Erythrocytes as carrier for prednisolone: in vitro and in vivo evaluation.

Resealed erythrocytes, as drug delivery system has tremendous potential to achieve site specificity and prolonged release of drug thereby enhancing therapeutic index and patient compliance. In the present investigation erythrocytes obtained from healthy volunteers were loaded with prednisolone using preswell dilution and dilution technique with two different cross-linking agents, glutaraldehyde and dimethylsulphoxide. Carrier erythrocytes, having acceptable loading parameters showed increased percentage drug content with the addition of cross-linking agents. In vitro drug release followed zero-order kinetics, haemoglobin content was found to be satisfactory and osmotic fragility study indicated that increased drug entrapment efficiency was found at 0.3%w/v concentration of sodium chloride (hypotonic solution). In vivo tissue distribution studies were carried out for optimized formulation and order of distribution was found to be Liver>Lung>Kidney> Spleen. The developed drug delivery system is endowed with several exclusive advantages and hence holds potential for further research and clinical application.

Multiparticulate drug delivery system of aceclofenac: development and in vitro studies.

The aim of this study was to develop an enteric-coated multiunit dosage form containing aceclofenac, a nonsteroidal anti-inflammatory drug. The pellets were prepared by using extrusion/spheronization method, and the core pellets were coated with a pH-sensitive poly(meth) acrylate copolymer (Eudragit L100-55) to achieve site-specific drug release. The formulated pellets were characterized for percentage yield, size distribution, surface morphology studies, drug content, and flow properties. In vitro dissolution test was used for comparison of drug release profiles of various coated pellets. The practical yield was found to be 90-95%. The particle size of enteric-coated pellets was found to be in the range of 0.59-0.71 mm. The pellets were spherical in shape and surfaces of pellets were found to be rough and showing micropores. Enteric-coated pellets showed good flow properties and in vitro dissolution profile. Dissolution tests were carried out in a USP type II dissolution apparatus in media-simulating pH conditions of the gastrointestinal tract. The release of the aceclofenac from formulated pellets was established to be minimum in the pH 1.2 (<5%) for a period of 2 h, and at pH 6.8, it shows the maximum release (85 +/- 5% release within 1 h) which indicates gastric resistance of the formulated pellets. The 20% wt/wt enteric-coated pellets were compared to that of marketed product (tablets), it was observed that pellets showed better release profile. The study concluded that the formulated multiparticulate dosage forms can be used as an ideal drug delivery system for the aceclofenac.

Development of mucoadhesive buccal films for the treatment of oral sub-mucous fibrosis: a preliminary study.

The objective of the present study was to develop the mucoadhesive buccal film of valdecoxib for the treatment of oral sub mucous fibrosis, a localized buccal disease. Valdecoxib, a novel COX-2 inhibitor has been reported to be used in various osteopathic and rheumatoid conditions as oral therapy. The films were made out of chitosan and HPMC K4M as polymers. Sodium taurocholate was used as a permeation enhancer. All the formulations were examined for film thickness, swelling properties, drug content, weight variation, in vitro release studies, bioadhesive force, tensile strength, diffusion studies using pig mucosa and pharmacokinetic study in healthy male volunteers. Prepared films were thin, flexible, smooth and transparent. Bioadhesive force and tensile strength of the optimized formulation were found to be 75 +/- 4 kg m(-1) S(-2) and more than 2.5 kg/3 cm(2), respectively. The percent drug content was 98.5 +/- 1.3%. The in vitro drug release from the selected formulation showed that about 69.34% of the drug payload was released up to 6 hours. The drug permeation through the dialysis sac and pig buccal mucosa was found to be 62.70% and 54.39%, respectively. Pharmacokinetic studies of the buccal mucoadhesive film showed that the drug was released locally at the target site of action, and a very small amount might have absorbed systemically.

Development and in vivo evaluation of functionalized ritonavir proliposomes for lymphatic targeting.

AIMS: The aim of the present work was to prepare, characterize, and evaluate proliposomes containing lipophilic prodrug ritonavir for targeting towards CD4+ T cells in the lymphatic system. MATERIALS AND METHODS: The liposomes were prepared by lipid thin film hydration method and lyophilized in the presence of cryoprotectant mannitol to obtain proliposomes. The optimized proliposomes by Central Composite Design, were surface modified with biotin. The proliposomes were evaluated for particle size, zeta potential, polydispersity index (PDI), entrapment efficiency, in vitro drug release, in vivo pharmacokinetics and biodistribution studies. KEY FINDINGS: The mean particle size was found to be in the range of 126.6 to 306.2nm with PDI of 0.340-1.00. The entrapment efficiency was found to be in the range of 18.9 to 86.2%. The formulations showed a zeta potential in the range of -18.1 to -20.2mv. Biotinylated proliposomes (LIP-5B) were in the size of 149.8±6.8nm with entrapment efficiency 61.6%. The % CDR of pure drug, conventional, biotinylated proliposome in 3h was found to be 58.3, 82.04, and 95.9% respectively. In vitro drug release and in vivo pharmacokinetics of the pure drug, optimized conventional proliposomes (LIP-5) and biotin proliposomes (LIP-5B) were executed. SIGNIFICANCE: The AUC for the liposomes were found to be much higher in the spleen and thymus compared to that in the plasma which indicated that the developed formulations enhance the bioavailability and target specificity compared to that of the pure drug thereby enhancing bioavailability at target site.

A novel long-acting biodegradable depot formulation of anastrozole for breast cancer therapy.

The purpose of the present study was to fabricate PLGA 50:50 and PLA microspheres for controlled delivery of anastrozole. The microspheres were prepared by oil-in-water (o/w) emulsion/solvent evaporation technique and evaluated for particle size and encapsulation. The optimised formulations were studied for solid state characterization, in vitro release and pharmacokinetic studies. The maximum encapsulation efficiency for PLGA 50:50 and PLA microspheres with 40:1 polymer - drug ratio was observed to be 78.4±2.5 and 87.7±2.6%. The solid state characterization confirmed dispersion of drug at the molecular level in the polymeric matrix. Microspheres were spherical in shape with a very smooth surface texture. Drug release was found to be in a sustained fashion, releasing constantly up to 720h (30days) for PLGA and 60days for PLA microspheres. The pharmacokinetic study data revealed that the intramuscular administration of PLA microspheres showed improved pharmacokinetic profile as compared to PLGA microspheres, and therefore this formulation can be considered as the best optimised formulation with sustained exposure of the drug in vivo compared to other microspheres. From experimental results, PLA microspheres demonstrate the feasibility of employing biodegradable depot polymeric microspheres of anastrozole for long-term treatment of breast cancer.

Development and evaluation of carboplatin-loaded PCL nanoparticles for intranasal delivery.

CONTEXT: The study was aimed to develop a polymeric nanoparticle formulation of anticancer drug carboplatin using biodegradable polymer polycaprolactone (PCL). The formulation is intended for intranasal administration to treat glioma anticipating improved brain delivery as nasal route possess direct access to brain and nanoparticles have small size to overcome the mucosal and blood-brain barrier. OBJECTIVE: Development and evaluation of carboplatin-PCL nanoparticles for brain delivery by nasal route. METHODOLOGY: Carboplatin-loaded PCL nanoparticles (CPCs) were prepared by double emulsion-solvent evaporation technique and characterized by particle size, zeta potential, entrapment efficiency, scanning electron microscopy and differential scanning calorimetry. The CPCs were assessed for in vitro release kinetics, ex vivo permeation and in situ nasal perfusion. Cytotoxic potential of CPCs in vitro was evaluated on LN229 human glioblastoma cells. RESULTS AND DISCUSSION: The optimized formulation of carboplatin-PCL nanoparticle CPC-08 with particle size of 311.6 ± 4.7 nm and zeta potential -16.3 ± 3.7 mV exhibited percentage entrapment efficiency of 27.95 ± 4.21. In vitro drug release showed initial burst release followed by slow and continues release indicating biphasic pattern. The ex vivo permeation pattern through sheep nasal mucosa also exhibited a similar release pattern as for in vitro release studies. In situ nasal perfusion studies in Wistar rats demonstrate that CPCs show better nasal absorption than carboplatin solution. In vitro cytotoxicity studies on LN229 cells showed an enhancement in cytotoxicity by CPCs compared to carboplatin alone. CONCLUSION: CPC-08 effectively improves nasal absorption of carboplatin and can be used for intranasal administration of carboplatin for improved brain delivery.

Development of risperidone liposomes for brain targeting through intranasal route.

The present paper is aimed at development of functionalized risperidone liposomes for brain targeting through nasal route for effective therapeutic management of schizophrenia. The risperidone liposomes were prepared by thin film hydration method. Various parameters such as lipid ratio and lipid to drug ratio were optimized by using Design-Expert(®) Software to obtain high entrapment with minimum vesicle size. The surface of the optimized liposomes was modified by coating stearylamine and MPEG-DSPE for enhanced penetration to the brain. The formulations were evaluated for vesicle size, zeta potential, and entrapment efficiency. The morphology was studied by Transmission Electron Microscopy (TEM). In vivo efficacy was assessed by performing pharmacokinetic study in Wistar albino rats following intranasal administration of the formulations in comparison to intravenous bolus administration of pure drug. The mean vesicle size of optimized liposomes ranged from 90 to 100nm with low polydispersity index (<0.5). The entrapment efficiency of optimized liposomes was between 50 and 60%, functionalized liposomes showed maximum entrapment. The TEM images showed predominantly spherical vesicles with smooth bilayered surface. All formulations showed prolonged diffusion controlled drug release. The in vivo results showed that liposomal formulations provided enhanced brain exposure. Among the formulations studied, PEGylated liposomes (LP-16) had shown greater uptake of risperidone into the brain than plasma. High brain targeting efficiency index for LP-16 indicating preferential transport of the drug to brain. The study demonstrated successful formulation of surface modified risperidone liposomes for nasal delivery with brain targeting potential.

A novel nanoproliposomes of lercanidipine: Development, in vitro and preclinical studies to support its effectiveness in hypertension therapy.

AIM: The aim of the present study was to develop nanoproliposomes of lercanidipine, in order to overcome its poor biopharmaceutical properties and to improve its therapeutic efficacy in treating hypertension. MAIN METHODS: The nanoproliposomes were prepared using a modified thin-film hydration method, and the formula was optimized by varying the ratio of lipids and the types of cryoprotectants. This optimized formulation was characterized in terms of its particle size, solid-state, drug release, in-situ absorption, in-vivo pharmacokinetics, and in-vivo anti-hypertensive activity in DOCA-salt induced hypertensive rats. Finally, a PK-PD correlation was established in order to understand the clinical implications of the developed novel nanoproliposomes. KEY FINDINGS: The nanoproliposomes showed a particle size of 174.7nm and an entrapment efficiency of 85.4%. The in-vitro release displayed initial rapid release (19.33%) followed by a sustained release profile, releasing 88.37% of the encapsulated drug. The in-situ studies showed a significant increase in absorption rate across the rat intestinal membrane. The pharmacokinetics of this novel form indicated a 2.75-fold increase in the absolute bioavailability as compared to pure lercanidipine. In addition, the nanoproliposomes were found to be efficient in treating hypertension in DOCA-salt induced hypertensive rats. The PK-PD correlation demonstrated no time lag between effect and exposure, indicating that a direct PK-PD relationship can be expected in the clinic. SIGNIFICANCE: These findings suggest that nanoproliposomes are promising carriers in improving the oral bioavailability and bioactivity of lercanidipine, and can be an effective therapy in the management of hypertension.

Nanomedicine of anastrozole for breast cancer: Physicochemical evaluation, in vitro cytotoxicity on BT-549 and MCF-7 cell lines and preclinical study on rat model.

AIM: Formulation and evaluation of anastrozole, an anti-cancer drug loaded in different biodegradable polymeric nanoparticles. MATERIALS AND METHODS: Different carrier systems such as poly(lactide-co-glycolide) (PLGA 50:50), poly(lactic-acid) (PLA) and poly(ε-caprolactone) (PCL) are used to prepare nanoparticles by simple emulsion technique. The surfactants polyvinyl alcohol and sodium deoxycholate were studied for their use as stabilizing agents at varying concentrations. The formulations were studied for their particle size, zeta potential, entrapment efficiency and solid state characteristics, and also were tested for their in vitro cytotoxicity and in vivo behavior in rats. KEY FINDINGS: The entrapment ranged from 35 to 85%, depending on the drug-polymer ratio used. Particle size ranged from 100 to 350nm with optimal zeta potential. Accordingly, discrete spherical nanoparticles with smooth surface were obtained as evidence from Field Emission Scanning Electron Microscopy (FESEM) study. The solid state characteristics revealed dispersion of drug at the molecular level in the polymeric matrix of nanoparticles. A non-Fickian transport with initial burst release followed by slow release was observed with nanoparticles. The remarkable decrease in cell viability at various time points was observed for PLGA nanoparticles compared to other polymer matrices. The AUC(0→∞) of PLGA, PLA and PCL nanoparticles were found to be 4.77, 19.31 and 19.81 fold higher than (p<0.05) anastrozole in solution, respectively. Also, pharmacokinetics study revealed the long time circulation of anastrozole loaded polymeric nanoparticles. SIGNIFICANCE: The results suggest that developed nanoparticles could be used successfully for effective management of breast cancer chemotherapy.

Supercritical fluid technology: concepts and pharmaceutical applications.

In light of environmental apprehension, supercritical fluid technology (SFT) exhibits excellent opportunities to accomplish key objectives in the drug delivery sector. Supercritical fluid extraction using carbon dioxide (CO(2)) has been recognized as a green technology. It is a clean and versatile solvent with gas-like diffusivity and liquid-like density in the supercritical phase, which has provided an excellent alternative to the use of chemical solvents. The present commentary provides an overview of different techniques using supercritical fluids and their future opportunity for the drug delivery industry. Some of the emerging applications of SFT in pharmaceuticals, such as particle design, drug solubilization, inclusion complex, polymer impregnation, polymorphism, drug extraction process, and analysis, are also covered in this review. The data collection methods are based on the recent literature related to drug delivery systems using SFT platforms. SFT has become a much more versatile and environmentally attractive technology that can handle a variety of complicated problems in pharmaceuticals. This cutting-edge technology is growing predominantly to surrogate conventional unit operations in relevance to the pharmaceutical production process. LAY ABSTRACT: Supercritical fluid technology has recently drawn attention in the field of pharmaceuticals. It is a distinct conception that utilizes the solvent properties of supercritical fluids above their critical temperature and pressure, where they exhibit both liquid-like and gas-like properties, which can enable many pharmaceutical applications. For example, the liquid-like properties provide benefits in extraction processes of organic solvents or impurities, drug solubilization, and polymer plasticization, and the gas-like features facilitate mass transfer processes. It has become a much more versatile and environmentally attractive technology that can handle a variety of complicated problems in pharmaceuticals. This review is focused on different techniques that use supercritical fluids and their opportunities for the pharmaceutical sector.

Controlled release chitosan microspheres of mirtazapine: in vitro and in vivo evaluation.

The purpose of the study was to formulate and evaluate controlled release chitosan microspheres of mirtazapine (MTZ) to improve the bioavailability by altering the pharmacokinetic profiles of the drug. Chitosan microspheres were prepared to prolong the release of the drug into the systemic circulation. Microspheres were prepared by a single water in oil (w/o) emulsion technique varying the chitosan/drug ratio, stirring speed and concentration of the crosslinking agent (glutaraldehyde). Drug-polymer compatibility studies were carried out using fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The microspheres were evaluated for encapsulation efficiency, particle size, surface morphology, swelling index, in vitro release, as well as erosion and in vivo studies in rats. The FT-IR and DSC studies revealed no interaction between drug and polymer. The encapsulation efficiency of different formulation varied from 53 ± 1.2% to 78 ± 1.5%. The mean particle size of the optimized formulation F-14 was 106.4 ± 0.5 µm. Surface morphology revealed that chitosan microspheres were discrete and spherical in shape with a porous surface. The release of MTZ from chitosan microspheres was rapid up to 4 h, and then it was continuously and slowly released up to 48 h. Optimized formulation (F-14) was found to be stable under accelerated storage conditions based on International Conference on Harmonisation guidelines. Pharmacokinetic studies revealed that the optimized formulation showed significant increases in systemic exposure (AUC = 177.70 ± 7.39 µg·h/mL), half-life (4.72 ± 0.46 h) and reduced clearance (0.009 ± 0.0001 L/h) compared to pure drug administration. Hence, the present study demonstrates that controlled release formulation of MTZ microspheres using chitosan can improve pharmacokinetic profiles of MTZ.

Evaluation of pharmacokinetic, biodistribution, pharmacodynamic, and toxicity profile of free juglone and its sterically stabilized liposomes.

The present study was aimed to formulate and compare the pharmacokinetic, biodistribution, pharmacodynamic, and toxicity profiles of free 5-hydroxy-1,4-naphthoquinone (juglone) with sterically stabilized liposomal form. The liposomes were optimized for size, zeta potential, entrapment efficiency (EE), and in vitro release properties. The optimized formulation had a mean size, zeta potential, and EE value of 137.1 nm, -43.1 mV, and 67.2%, respectively. In vitro release studies showed biphasic pattern with initial burst followed by sustained release over the study period, releasing about 61% after 24 h. In vitro cytotoxicity studies against melanoma cells indicated that liposomal juglone was more toxic than free juglone. Free juglone had short plasma half-life of about 2 h, whereas liposomal juglone exhibited significantly improved pharmacokinetics with a 12-fold increase in plasma half-life. Further, biodistribution studies indicated rapid renal elimination of free juglone, evidenced by its significant localization in kidneys. Conversely, the accumulation of liposomal juglone in kidneys reduced significantly with enhanced tumor localization, thereby resulting in enhanced antitumor activity. The histological studies revealed lower levels of nephrotoxicity for liposomal juglone compared with that of free juglone. To conclude, sterically stabilized liposomes could be a promising approach for the intravenous delivery of hydrophobic compounds such as juglone.

In vitro sustained release of calcium ions and pH maintenance from different vehicles containing calcium hydroxide.

INTRODUCTION: Calcium hydroxide is widely used as an intracanal medicament in endodontics. Its therapeutic effects depend on the dissociation of calcium hydroxide into calcium and hydroxyl ions, which, in turn, depends on the vehicle used. The purpose of this in vitro study was to evaluate the sustained release of calcium ions and the pH change of calcium hydroxide over a period of 30 days when formulated with propylene glycol, polyethylene glycol 6000, chitosan, and guar gum. METHODS: Various formulations were prepared and placed inside the root canals of human teeth and were suspended in glass vials containing distilled water. At specific time intervals, the calcium ion concentration was analyzed using an ultraviolet spectrophotometer. pH changes of the medium were measured at various time intervals up to 30 days. RESULTS: Results revealed that chitosan formulation showed the maximum sustained release of calcium ions compared with the other three formulations. All the formulations exhibited high alkaline pH upto 30 days. CONCLUSION: From the results of this in vitro study, it can be concluded that chitosan can be used as a promising vehicle for for the sustained release of calcium ions from the calcium hydroxide in the root canal system.

Preparation, in vitro characterization, pharmacokinetic, and pharmacodynamic evaluation of chitosan-based plumbagin microspheres in mice bearing B16F1 melanoma.

The present study was aimed to evaluate the anti-tumor efficacy and systemic toxicity of chitosan-based plumbagin microspheres in comparison to free plumbagin. The optimized formulation had a mean particle size of 106.35 mum with an encapsulation efficiency of 80.12%. Pharmacokinetic studies showed a 22.2-fold increase in elimination half-life (t(1/2)) of plumbagin from chitosan microspheres as compared to free plumbagin. Administration of plumbagin microspheres resulted in a significant tumor growth inhibition and reduced systemic toxicity. These results suggest that chitosan-based microspheres could be a promising strategy for the systemic delivery of anti-cancer agents like plumbagin.

Gender differences in the pharmacokinetics of rivastigmine in rats.

The effect of gender on the pharmacokinetics of rivastigmine (CAS 123441-03-2) was studied in male and female Wistar rats following intravenous bolus administration. The area under the plasma concentration-time curve (AUC), apparent volume of distribution (Vd), systemic clearance (CL), and terminal plasma halflife (t1/2) of rivastigmine were compared between male and female rats. Compared to male rats, female rats exhibited higher plasma rivastigmine levels showing significantly (p < 0.05) larger AUC (226.77 vs. 149.68 ng h/ml), Vd (6.70 vs. 4.13 L), t1/2 (0.84 vs. 0.34 h) and a lower CL (5.51 vs. 8.35 L/h). The male rats had a 2.5 fold greater elimination rate constant than female rats (2.02 vs. 0.82 h(-1)). Gender had a significant effect on the pharmacokinetics of rivastigmine. Gender differences were reported due to gonadal hormones, and the observed difference in pharmacokinetics of rivastigmine might be attributed to testosterone in male rats.

Chronotherapeutic drug delivery for early morning surge in blood pressure: a programmable delivery system.

The purpose of the study was to develop pulsatile capsule dosage form of valsartan for controlled delivery. In the majority of individuals blood pressure rises in the early morning hours, which lead to serious cardiovascular complications. Formulations with constant/programmable delivery rates make it possible to deliver drug at definite time or controlled rate in chronopharmacokinetic studies. The prepared system contained swellable polymer (l-hydroxypropyl cellulose (L-HPC), xanthan gum, polyethylene oxide or sodium alginate) together with drug tablet and erodible tablet (L-HPC or guar gum) in a pre-coated capsule. Various formulation factors were investigated through series of tests, in vitro dissolution and ex vivo continuous dissolution-absorption studies. We found that the type, amount of polymers and erodible tablet influenced the drug release. The formulation containing 200 mg sodium alginate and erodible tablet (150 mg) containing 50% guar gum and 46% lactose showed 5-6 h lag time and 10+/-2.1% drug release in initial 6 h following rapid release (99+/-1.7% release in 12 h) of drug was observed. The continuous dissolution-absorption study conducted using everted rat intestinal segment indicated delay in absorption of drug. Thus this approach can provide a useful means for timed release of valsartan and may be helpful for patients with morning surge.