Drug release and swelling kinetics of directly compressed glipizide sustained-release matrices: establishment of level A IVIVC.

The purpose of this study was to examine a level A in vitro-in vivo correlation (IVIVC) for glipizide hydrophilic sustained-release matrices, with an acceptable internal predictability, in the presence of a range of formulation/manufacturing changes. The effect of polymeric blends of ethylcellulose, microcrystalline cellulose, hydroxypropylmethylcellulose, xanthan gum, guar gum, Starch 1500, and lactose on in vitro release profiles was studied and fitted to various release kinetics models. Water uptake kinetics with scanning electron microscopy (SEM) was carried out to support the drug release mechanism. An IVIVC was established by comparing the pharmacokinetic parameters of optimized (M-24) and marketed (Glytop-2.5 SR) formulations after single oral dose studies on white albino rabbits. The matrix M-19 (xanthan:MCC PH301 at 70:40) and M-24 (xanthan:HPMC K4M:Starch 1500 at 70:25:15) showed the glipizide release within the predetermined constraints at all time points with Korsmeyer-Peppas' and zero-order release mechanism, respectively. Kopcha model revealed that the xanthan gum is the major excipient responsible for the diffusional release profile and was further supported by SEM and swelling studies. A significant level A IVIVC with acceptable limits of prediction errors (below 15%) enables the prediction of in vivo performance from their in vitro release profile. It was concluded that proper selection of rate-controlling polymers with release rate modifier excipients will determine overall release profile, duration and mechanism from directly compressed matrices.

Nateglinide quantification in rabbit plasma by HPLC: optimization and application to pharmacokinetic study.

A rapid, simple, and sensitive HPLC method with UV detection was developed and validated for the determination of nateglinide (NTG) from rabbit plasma. The retention behavior of NTG and gliclazide (GLZ, internal standard-IS) as a function of mobile phase pH, composition and flow rate was investigated. Separation was developed on a reverse-phase C(18) column (250 mm x 4.6mm i.d., 5 microm particle size), using a mixture of acetonitrile (ACN):10mM phosphate buffer (PBS, pH 3.0) in the ratio of 70:30(%v/v) at a flow rate of 1.0 ml/min with UV detection at 203 nm within 8 min, and quantified based on drug/IS peak area ratios. The plasma samples were prepared by a simple deproteinization with a mixture of methanol and acetonitrile, yielding more than 97.86% extraction efficiencies. The calibration curve was linear (correlation coefficient of 0.9984) in the concentration range of 10-2500 ng/ml. The limit of detection (LoD) and limit of quantitation (LoQ) were found to be 2.91 and 9.70 ng/ml, respectively. Both the intra-day and inter-day precisions at four tested concentrations were below 1.32% R.S.D. The present method was selective enough to analyze NTG in rabbit plasma without any tedious sample clean-up procedure and was successfully applied for estimating the pharmacokinetic parameters of NTG following oral administration of a single 15 mg NTG to white albino rabbits.

Reversed chitosan-alginate polyelectrolyte complex for stability improvement of alpha-amylase: optimization and physicochemical characterization.

The present work explores, using response surface methodology, the main and interaction effects of some process variables on the preparation of a reversed chitosan-alginate polyelectrolyte complex (PEC) with entrapped alpha-amylase for stability improvement. A 3(3) full factorial design was used to investigate the effect of the chitosan and alginate concentrations and hardening time on the percent entrapment, time required for 50% (T(50)) and 90% (T(90)) enzyme release, and particle size. The beads were prepared by dropping chitosan containing alpha-amylase into a sodium alginate solution without any salt. The in vitro enzyme release profile of the beads was fitted to various release kinetics models to study the release mechanism. A topographical characterization was carried out using scanning electron microscopy (SEM), and the entrapment was confirmed using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). Stability testing was carried out according to the International Conference on Harmonization (ICH) guidelines for zones III and IV. Beads prepared using 2.5%w/v chitosan and 3%w/v sodium alginate with a hardening time of 60 min had more than 90% entrapment and a T(90) value greater than 48 min. Moreover, the shelf-life of the enzyme-loaded beads was found to increase to 3.68 years, compared with 0.99 years for the conventional formulation. It can be inferred that the proposed methodology can be used to prepare a reversed PEC of chitosan and alginate with good mechanical strength, provided both the reactants are in a completely ionized form at the time of the reaction. Proper selection of the reaction pH, polymer concentration and hence charge density, and hardening time is important and determines the characteristics of the PEC.

Physicochemical characterization of papain entrapped in ionotropically cross-linked kappa-carrageenan gel beads for stability improvement using Doehlert shell design.

This work examines the influence of various process parameters on papain entrapped in cross-linked kappa-carrageenan beads for improvement of its stability. A Doehlert shell design (DSD) was employed to investigate the effect of three process variables, namely kappa-carrageenan concentration, KCl concentration, and hardening time, on the entrapment, time required for 50% enzyme release (T50), time required for 90% enzyme release (T90), and particle size. The beads were prepared by dropping the kappa-carrageenan containing papain into a magnetically stirred KCl solution. Topographical characterization was carried out by scanning electron microscopy and entrapment was confirmed by Fourier transform infrared spectroscopy and differential scanning calorimetry. Stability testing was carried out according to the International Conference on Harmonization (ICH) guidelines for zone III and IV. A polymeric matrix was prepared with kappa-carrageenan (3.5% w/v) and potassium chloride (0.5 M) using the ionotropic gelation method, with a hardening time of 20 min. Beads characterized by a spherical disc shape with a collapsed center, an absence of aggregates, an entrapment of 82.75%, a T90 value of 55.36 min, and a composite index of 88.55 were produced. The shelf-life of the enzyme-loaded beads was found to increase to 3.63 years compared with 1.01 years for the conventional formulation. It can be inferred that the proposed methodology can be used to prepare papain-loaded kappa-carrageenan beads for stability improvement.

Stability improvement of alpha-amylase entrapped in kappa-carrageenan beads: physicochemical characterization and optimization using composite index.

PURPOSE: This work examines the influence of various process parameters on alpha-amylase entrapped in crosslinked kappa-carrageenan beads for stability improvement. A three level full factorial design was employed to investigate the effect of three process variables namely kappa-carrageenan concentration, potassium chloride concentration and hardening time on % entrapment, time required for 50% (T50) and 90% (T90) of enzyme release and particle size. METHODS: The beads were prepared by dropping the kappa-carrageenan-containing alpha-amylase to magnetically stirred potassium chloride solution. The composite index was applied to optimize the process under study. 'In vitro' enzyme release profile of the beads was fitted to various release kinetics models to understand the release mechanism. Topographical characterization was carried out by SEM and entrapment was confirmed by FTIR and DSC. Stability testing according to the ICH guidelines for zone III and IV was carried out. RESULTS: With the use of ionotropic gelation method, a polymeric matrix prepared by 3.5% (w/v) kappa-carrageenan, 0.7 M potassium chloride and hardening time of 30 min resulted in the production of beads characterized by disc shaped with collapsed center, absence of aggregates, % entrapment of 73.79, T90 of 74.4 min, and composite index of 83.01. Moreover, shelf-life of the enzyme loaded beads was found to increase up to 3.53 years compared to 0.99 year of the conventional formulation. CONCLUSIONS: It can be inferred that the proposed method can be used to prepare alpha-amylase loaded kappa-carrageenan beads for stability improvement. Also the proper selection of rate-controlling carrageenan concentration and its interactive potential for crosslinking is important and will determine the overall size and shape of beads, the duration and pattern of dissolution profiles and enzyme loading capacity.

Papain entrapment in alginate beads for stability improvement and site-specific delivery: physicochemical characterization and factorial optimization using neural network modeling.

This work examines the influence of various process parameters (like sodium alginate concentration, calcium chloride concentration, and hardening time) on papain entrapped in ionotropically cross-linked alginate beads for stability improvement and site-specific delivery to the small intestine using neural network modeling. A 3(3) full-factorial design and feed-forward neural network with multilayer perceptron was used to investigate the effect of process variables on percentage of entrapment, time required for 50% and 90% of the enzyme release, particle size, and angle of repose. Topographical characterization was conducted by scanning electron microscopy, and entrapment was confirmed by Fourier transform infrared spectroscopy and differential scanning calorimetry. Times required for 50% (T(50)) and 90% (T(90)) of enzyme release were increased in all 3 of the process variables. Percentage entrapment and particle size were found to be directly proportional to sodium alginate concentration and inversely proportional to calcium chloride concentration and hardening time, whereas angle of repose and degree of cross-linking showed exactly opposite proportionality. Beads with >90% entrapment and T(50) of <10 minutes could be obtained at the low levels of all 3 of the process variables. The inability of beads to dissolve in acidic environment, with complete dissolution in buffer of pH >or=6.8, showed the suitability of beads to release papain into the small intestine. The shelf-life of the capsules prepared using the papain-loaded alginate beads was found to be 3.60 years compared with 1.01 years of the marketed formulation. It can be inferred from the above results that the proposed methodology can be used to prepare papain-loaded alginate beads for stability improvement and site-specific delivery.

Effect of pH on in vitro permeation of ondansetron hydrochloride across porcine buccal mucosa.

The influence of drug concentration, pH in donor chamber, and 1-octanol/buffer partition coefficient on transbuccal permeation of ondansetron hydrochloride (pKa, 7.4) across porcine buccal mucosa was studied by using an in-line Franz type diffusion cell at 37 degrees C. The pH was adjusted to several values and the solubility of the drug in different pH was measured. Solubility of ondansetron hydrochloride decreases with increasing pH. The permeability of the drug was evaluated at different donor pH and drug concentrations. Permeability of un-ionized (Pu) and ionized (Pi) species of drug was calculated by fitting the data to a mathematical model. The steady state flux increased linearly with the donor concentration (r2 = 0.9843) at pH 7.4. The permeability coefficient and the partition coefficient of the drug increased with increasing pH. The values of Pu and Pi were 4.86 x 10(-6) cm/sec and 7.18 x 10(-7) (c)m/sec, respectively. The observed permeability coefficients and the permeability coefficients calculated from the mathematical model at various pH showed good linearity (r2 = 0.9799). The total permeability coefficient increased with increasing the fraction of un-ionized form of the drug. The drug permeated through buccal mucosa by a passive diffusion process. The non-ionized species of drug penetrated well through buccal mucosa and the permeation was a function of pH. Transbuccal delivery is a potential route for the administration of ondansetron hydrochloride.

Estimation of trace amounts of chromium(III) in multi-vitamin with multi-mineral formulations.

Two new specific, selective, simple and inexpensive spectroscopic methods for estimating a trace amount of chromium (Cr3+) from a multi-vitamin with multi-mineral pharmaceutical formulations were developed. The proposed methods are based on the conversion of Cr3+ to Cr6+ either by oxidation with a nitric acid-perchloric acid mixture (method I) or by fusion with an excess amount of sodium carbonate (method II), followed by the complexation of Cr6+ with 1,5-diphenylcarbazide (DPC) in a mineral acidic solution of pH 1.0 +/- 0.5. The pink-colored complex was estimated at 544 nm. Both methods were found to be linear in the range of 0.1 - 0.8 microg/ml with a limit of detection in the range of 0.0123 - 0.0157 microg/ml and a limit of quantitation in the range of 0.0419 - 0.0525 microg/ml. Method I was found to be suitable for estimating Cr3+ species in various formulations, like tablets, capsules and syrups, while method II was found to be suitable for tablets and capsules. Satisfactory recovery from spiked samples of standard Cr3+ suggests no interference of any excipients and diverse ions present in the formulations. The developed methods were compared with AAS by ANOVA, and no significant difference was observed.