Targeting enteral endocrinal L-cells with dietary carbohydrates, by increasing the availability of miglitol in the intestinal lumen, leads to multi-fold enhancement of plasma glucagon-like peptide-1 levels in non-diabetic canines.

The principle aim of this study was to design a controlled release (CR), bioadhesive formulation of miglitol (in form of pellets) which would regulate the post-prandial glucose levels via reversible inhibition of α-glucosidase enzyme as well as by modulating the glucagon-like peptide-1 (GLP-1) pathway in non-diabetic canines. A multilayered pellet formulation which was both bioadhesive (because of hydroxy propyl methyl cellulose polymer) and CR (because of the ethyl cellulose layer) was formulated. We report a novel finding that the CR formulation of miglitol (S3) induced a 2.2-fold elevation in the C(max) as well as the overall AUC(0-24) of GLP-1 values in comparison to the non-CR (immediate release (IR) formulation). The S3 formulation also resulted in better, steady, and prolonged control of glucose levels over a time period of 7 h in comparison to the IR formulation possibly due to combination of both, prolonged inhibition of the α-glucosidase enzyme and enhanced plasma GLP-1 levels. The S3 formulation was stable with no changes in the dissolution profiles at both of the stability conditions tested, 25°C/60% RH and 40°C/75% RH. Aqueous polymeric coating of the pellets (in contrast to coating using organic solvents) resulted morphologically in a uniform polymeric film and also releases profiles with lower burst effect. Curing played a significant role in determining release profile of the pellets, prepared by aqueous polymeric coating method.

Core-in-cup tablet design of metoprolol succinate and its evaluation for controlled release.

The core-in-cup matrix tablets of Metoprolol succinate were prepared by wet granulation technique. Of all the investigated formulations, the optimized formulation of MS-09 followed zero-order kinetics of drug release. Trail on MS-09 was formulated using 7.5% hydrogenated castor-oil (HCO) and 4% of hydroxyl propyl methylcellulose (HPMC K15M) with an objective to achieve a linear release profile for 24 h. There is no initial burst release, with 16.17% of drug released during the first hour and release was extended up to 24 hrs. Study of drug release kinetics was performed by application of dissolution data to various kinetic equations like zero-order; first order, Higuchi and Korsmeyer-Peppas, from R(2) value (0.9975) it was concluded that the drug release followed zero order kinetics with both erosion and diffusion as the release mechanisms.

Design and evaluation of oral bioadhesive controlled release formulations of miglitol, intended for prolonged inhibition of intestinal alpha-glucosidases and enhancement of plasma glucagon like peptide-1 levels.

Alpha-glucosidase enzyme is present ubiquitously throughout the lumen of the small intestine. It is responsible for the breakdown of complex into simple carbohydrates. alpha-Glucosidase inhibitors such as miglitol, are drugs that have greater affinity towards this enzyme in comparison to carbohydrates. Miglitol regulates the postprandial glucose levels directly by inhibiting the enzyme reversibly and also indirectly by including the secretion of glucagon like peptide-1 (GLP-1). The aims of this study were (i) to design a controlled release (CR) mucoadhesive (in the intestine) formulation of miglitol which would inhibit the alpha-glucosidase enzyme for a longer duration of time (in comparison to the non-controlled release (IR) formulation) thus reducing the dosing frequency, and also controlling the postprandial glucose levels more effectively over a longer period of time; (ii) to assess the effect of different formulation parameters on the release of miglitol in vitro from the CR pellets; (iii) to evaluate the mucoadhesion of pellets in the intestine ex vivo; (iv) to study the effect of formulation parameters on plasma GLP-1 levels; and (v) to find out the effect of formulations on postprandial glucose levels. The data obtained was analysed to find out whether there was a correlation between these different parameters. Four controlled release formulations (CR1, CR2, CR3 and CR4) of miglitol comprising of multilayered pellets were designed successfully. The CR4 formulation containing 30% of 20 cps of ethyl cellulose (the retarding layer of the formulation) displayed slowest release of miglitol in vitro in comparison to other formulations. We designed an ex vivo experimental setup for studying the mucoadhesion of the pellets in the lumen of the intestine. Results indicated that amongst all of the adherent pellets, 5% were found to be adhering in the duodenal region, 61% in the jejunum, 32% in the ileum and 2% in the colon. Two of the controlled release formulations CR1 and CR4 were evaluated in vivo in dogs. Both the formulations displayed significantly higher and more prolonged (greater AUC) levels of GLP-1 in comparison to either the placebo or the immediate release (IR) formulations. They even displayed a significantly better control of postprandial glucose in comparison to either placebo or IR formulations. However, a comparison between the two controlled release formulations (CR1 and CR4) revealed that the plasma GLP-1 (AUC by CR1=63.1+/-1.32 and CR4=66.2+/-0.82) and postprandial glucose values due to both the formulations were rather similar despite their differences in in vitro release as well as pharmacokinetic profiles (plasma miglitol AUC of CR1=16.17+/-4.11 and CR4=27.17+/-4.33).

Ketorolac tromethamine transdermal gel: development, in vitro and in vivo evaluation.

The authors developed and evaluated a transdermal gel formulation of ketorolac tromethamine (ketorolac) for the treatment of nociceptive somatic pain. The formulation was optimized for skin permeation enhancers, pH of the system, and dosage strength using in vitro and in vivo techniques. Of the various permeation enhancers evaluated, dimethyl sulfoxide (DMSO) and oleic acid were found to significantly increase skin permeation flux of ketorolac. The concentration of DMSO affected the rate as well as extent of transdermal absorption. Use of citric acid further improved the skin penetration of ketorolac. In vitro diffusion results indicated significant increase in drug permeation with increasing drug concentration. However, the same did not translate into higher skin permeation during in vivo study. Although the area under concentration time curve (AUC(0-t)) increased significantly with increasing dose, the effect on maximum serum concentration (C(max)) was insignificant. The formulation can be used for inflammatory pain management while avoiding gastric adverse events associated with oral ketorolac.

Lipid nanoparticles for transdermal delivery of flurbiprofen: formulation, in vitro, ex vivo and in vivo studies.

The aim of the study is to prepare aqueous dispersions of lipid nanoparticles--flurbiprofen solid lipid nanoparticles (FLUSLN) and flurbiprofen nanostructured lipid carriers (FLUNLC) by hot homogenization followed by sonication technique and then incorporated into the freshly prepared hydrogels for transdermal delivery. They are characterized for particle size, for all the formulations, more than 50% of the particles were below 300 nm after 90 days of storage at RT. DSC analyses were performed to characterize the state of drug and lipid modification. Shape and surface morphology were determined by TEM which revealed fairly spherical shape of the formulations. Further they were evaluated for in vitro drug release characteristics, rheological behaviour, pharmacokinetic and pharmacodynamic studies. The pharmacokinetics of flurbiprofen in rats following application of SLN gel (A1) and NLC gel (B1) for 24 h were evaluated. The Cmax of the B1 formulation was 38.67 +/- 2.77 microg/ml, which was significantly higher than the A1 formulation (Cmax = 21.79 +/- 2.96 microg/ml). The Cmax and AUC of the B1 formulation were 1.8 and 2.5 times higher than the A1 gel formulation respectively. The bioavailability of flurbiprofen with reference to oral administration was found to increase by 4.4 times when gel formulations were applied. Anti-inflammatory effect in the Carrageenan-induced paw edema in rat was significantly higher for B1 and A1 formulation than the orally administered flurbiprofen. Both the SLN and NLC dispersions and gels enriched with SLN and NLC possessed a sustained drug release over period of 24 h but the sustained effect was more pronounced with the SLN and NLC gel.

Development of SLN and NLC enriched hydrogels for transdermal delivery of nitrendipine: in vitro and in vivo characteristics.

The purpose of this research was to investigate novel particulate carrier systems such as solid lipid nanoparticles (SLN) and nanostructured lipid carrier (NLC) for transdermal delivery of nitrendipine (NDP). For this investigation, four different gel-forming agents were selected for hydrogel preparation. Aqueous dispersions of lipid nanoparticles made from trimyristin (TM) were prepared by hot homogenization technique followed by sonication and then incorporated into the freshly prepared hydrogels. The particle size was analyzed by photon correlation spectroscopy (PCS) using Malvern zetasizer, which shows that for all the tested formulations, more than 50% of the particles were below 250 nm after 90 days of storage at room temperature. DSC analysis was performed to characterize the state of drug and lipid modification. Shape and surface morphology were determined by scanning electron microscope (SEM) and transmission electron microscope (TEM), which revealed fairly spherical shape of the formulations. The antihypertensive activity of the gels in comparison with that of oral NDP was studied using desoxy corticosterone acetate (DOCA)-induced hypertensive rats. It was observed that both carbopol SLN (A1) and carbopol NLC (B1) gels significantly controlled hypertension from the first hour (p < .05). The developed gels increased the efficacy of NDP for the therapy of hypertension. Both the SLN and NLC dispersions and the gels enriched with SLN and NLC possessed a sustained drug release over a period of 24 h, but the sustained effect was more pronounced with the SLN and the NLC gel formulations. Further, they were evaluated for zeta potential, entrapment efficiency, in vitro release, ex vivo permeation, and skin irritation studies.

Design and evaluation of a novel matrix type multiple units as biphasic gastroretentive drug delivery systems.

A biphasic gastroretentive floating drug delivery system with multiple-unit mini-tablets based on gas formation technique was developed to maintain constant plasma level of a drug concentration within the therapeutic window. The system consists of loading dose as uncoated core units, and prolonged-release core units are prepared by direct compression process; the latter were coated with three successive layers, one of which is seal coat, an effervescent (sodium bicarbonate) layer, and an outer polymeric layer of polymethacrylates. The formulations were evaluated for quality control tests, and all the parameters evaluated were within the acceptable limits. The system using Eudragit RL30D and combination of them as polymeric layer could float within acceptable time. The drug release was linear with the square root of time. The rapid floating and the controlled release properties were achieved in this present study. When compared with the theoretical release profile, the similarity factor of formulation with coating of RS:RL (1:3)-7.5%, was observed to be 74, which is well fitted into zero-order kinetics confirming that the release from formulation is close to desired release profile. The stability samples showed no significant change in dissolution profiles (p > 0.05). In vivo gastric residence time was examined by radiograms, and it was observed that the units remained in the stomach for about 5 h.

Development of nitrendipine controlled release formulations based on SLN and NLC for topical delivery: in vitro and ex vivo characterization.

The aim of the investigation is to develop solid lipid nanoparticles (SLN) and nano-structured lipid carrier (NLC) as carriers for topical delivery of nitrendipine (NDP). NDP-loaded SLN and NLC were prepared by hot homogenization technique followed by sonication, and they were characterized for particle size, zeta potential, entrapment efficiency, stability, and in vitro release profiles. Also the percutaneous permeation of NDPSLN A, NDPSLN B, and NDPNLC were investigated in abdominal rat skin using modified Franz diffusion cells. The steady state flux, permeation coefficient, and lag time of NDP were estimated over 24 h and compared with that of control (NDP solution). The particle size was analyzed by photon correlation spectroscopy (PCS) using Malvern zeta sizer, which shows that the NDPSLN A, NDPSLN B, and NDPNLC were in the range of 124-300 nm during 90 days of storage at room temperature. For all the tested formulations (NDPSLN A, NDPSLN B, and NDPNLC), the entrapment efficiency was higher than 75% after 90 days of storage. The cumulative percentage of drug release at 24 h was found to be 26.21, 30.81, and 37.52 for NDPSLN A, NDPSLN B, and NDPNLC, respectively. The results obtained from in vitro release profiles also indicated the use of these lipid nanoparticles as modified release formulations for lipophilic drug over a period of 24 h. The data obtained from in vitro release from NDPSLN A, NDPSLN B, and NDPNLC were fitted to various kinetic models. High correlation was obtained in Higuchi and Weibull model. The release pattern of drug is analyzed and found to follow Weibull and Higuchi equations. The permeation profiles were obtained for all formulations: NDPSLN A, NDPSLN B, and NDPNLC. Of all the three formulations, NDPNLC provided the greatest enhancement for NDP flux (21.485 +/- 2.82 microg/h/cm(2)), which was fourfold over control (4.881 +/- 0.96 microg/h/cm(2)). The flux obtained with NDPSLN B (16.983 +/- 2.91 microg/h/cm(2)) and NDPNLC (21.485 +/- 2.82 microg/h/cm(2)) meets the required flux (16.85 microg/h/cm(2)).

Pharmacokinetics, tissue distribution and bioavailability of nitrendipine solid lipid nanoparticles after intravenous and intraduodenal administration.

PURPOSE: The aim of this research was to study whether the bioavailability of nitrendipine (NDP) could be improved by administering nitrendipine solid lipid nanoparticles (SLN) duodenally to rats. METHODS: Nitrendipine was incorporated into SLN prepared by hot homogenization followed by ultrasonication method. SLN were produced using various triglycerides (trimyristin, tripalmitin and tristearin), soy phosphatidylcholine 95%, poloxamer 188 and charge modifiers (dicetyl phosphate, DCP and stearylamine, SA). Particle size and charge measurements were made with a Malvern Zetasizer. Pharmacokinetics of nitrendipine SLNs (NDP-SLNs) after intravenous (i.v.) and intraduodenal (i.d.) administration to conscious male Wistar rats were studied. Tissue distribution studies of NDP-SLNs were carried out in Swiss albino mice after i.v. administration and compared to nitrendipine suspension (NDP-Susp). RESULTS: Average size and zeta potential of SLNs of different lipids, with and without charge modifiers ranged from 101.9 +/- 3.0 to 123.5 +/- 3.0 nm and - 35.1 +/- 0.5 to +34.6 +/- 2.3 mV, respectively. AUC(0-infinity) was increased (up to 4.51-folds) and clearance was decreased (up to 4.54-folds) after i.v. administration of NDP-SLNs with and without charge modifiers compared to NDP-Susp. Effective bioavailability of NDP-SLNs were 2.81-5.35-folds greater after i.d. administration in comparison with that of NDP-Susp. In tested organs, the AUC and MRT of NDP-SLNs were higher than those of NDP-Susp especially in brain, heart and reticuloendothelial cells containing organs. CONCLUSIONS: SLN are suitable drug delivery systems for the improvement of bioavailability of nitrendipine. Negatively and positively charged SLN were better taken up by the liver and brain, respectively.

Radioprotective effect of transferrin targeted citicoline liposomes.

The high level of expression of transferrin receptors (Tf-R) on the surface of endothelial cells of the blood-brain-barrier (BBB) had been widely utilized to deliver drugs to the brain. The primary aim of this study was to use transferrin receptor mediated endocytosis as a pathway for the rational development of holo-transferrin coupled liposomes for drug targeting to the brain. Citicoline is a neuroprotective agent used clinically to treat for instance Parkinson disease, stroke, Alzheimer's disease and brain ischemia. Citicoline does not readily cross the BBB because of its strong polar nature. Hence, citicoline was used as a model drug. (Citicoline liposomes have been prepared using dipalmitoylphosphatidylcholine (DPPC) or distearoylphosphatidylcholine (DSPC) by dry lipid film hydration-extrusion method). The effect of the use of liposomes composed of DPPC or DSPC on their citicoline encapsulation efficiency and their stability in vitro were studied. Transferrin was coupled to liposomes by a technique which involves the prevention of scavenging diferric iron atoms of transferrin. The coupling efficiency of transferrin to the liposomes was studied. In vitro evaluation of transferrin-coupled liposomes was performed for their radioprotective effect in radiation treated cell cultures. In this study, OVCAR-3 cells were used as a model cell type over-expressing the Tf-R and human umbilical vein endothelial cells (HUVEC) as BBB endothelial cell model. The average diameter of DPPC and DSPC liposomes were 138 +/- 6.3 and 79.0 +/- 3.2 nm, respectively. The citicoline encapsulation capacity of DPPC and DSPC liposomes was 81.8 +/- 12.8 and 54.9 +/- 0.04 microg/micromol of phospholipid, respectively. Liposomes prepared from DSPC showed relatively better stability than DPPC liposomes at 37 degrees C and in the presence of serum. Hence, DSPC liposomes were used for transferrin coupling and an average of 46-55 molecules of transferrin were present per liposome. Free citicoline has shown radioprotective effect at higher doses tested. Interestingly, encapsulation of citicoline in pegylated liposomes significantly improved the radioprotective effect by 4-fold compared to free citicoline in OVCAR-3 but not in HUVEC. Further, citicoline encapsulation in transferrin-coupled liposomes has significantly improved the radioprotective effect by approximately 8-fold in OVCAR-3 and 2-fold in HUVEC cells with respect to the free drug. This is likely due to the entry of citicoline into cells via transferrin receptor mediated endocytosis. In conclusion, our results suggest that low concentrations of citicoline encapsulated in transferrin-coupled liposomes could offer therapeutic benefit in treating stroke compared to free citicoline.

Quaternary salts of 4,3' and 4,4' bis-pyridinium monooximes. Part 2: synthesis and biological activity.

In continuation of our investigations of unsymmetrical bisquaternary monooximes, we synthesized four new series of compounds bridged by hexyl, heptyl, octyl and nonyl groups. All eight monooximes viz., dibromides of 1-(4-hydroxyiminomethylpyridinium)6-(3/4-carbamoylpyridinium)hexane, 1-(4-hydroxyiminomethylpyridinium)-7-(3/4-carbamoylpyridinium)heptane, 1-(4-hydroxyiminomethylpyridinium)-8-(3/4-carbamoylpyridinium)octane, 1-(4-hydroxyiminomethylpyridinium)-9-(3/4-carbamoylpyridinium)nonane as well as the corresponding bis-oximes were synthesized and characterized by spectral data. Their ability to reactivate tetraethylpyrophosphate (TEPP) inhibited mouse total brain cholinesterase was investigated and compared with the conventional oxime 2-pyridinealdoxime chloride (2-PAM). Mouse brain homogenate was used as the source of acetylcholinesterase. Among all the compounds, tested the compound with the hexylene bridge (6b) and a 3-carbamoyl group on the second pyridine ring was found to be the most active acetylcholinesterase reactivator (72%) which is greater than that of 2-PAM (56%). However, the activity was reversed; as the chain length increased from a heptylene to a nonylene bridge, they potentiated the inhibitory effect of TEPP rather than reactivation. It is interesting to note that compound 6b with a carbamoyl group at the 3rd position of the pyridine ring showed dose dependent reactivation whereas the corresponding compound 6a with the carbamoyl group present at the 4th position of the pyridine ring showed reactivation at lower concentration (30 microM) and potentiation of TEPP inhibition at higher concentrations (100 and 300 microM).

Pharmacokinetics, tissue distribution and bioavailability of clozapine solid lipid nanoparticles after intravenous and intraduodenal administration.

Clozapine, a lipophilic effective atypical antipsychotic drug, has very poor oral bioavailability (<27%) due to first pass effect. Clozapine solid lipid nanoparticles have been developed using various triglycerides (trimyristin, tripalmitin and tristearin), soylecithin 95%, poloxamer 188 and stearylamine as a positive charge inducer by hot homogenization followed by ultrasonication method. Particle size and charge measurements were made with Malvern Zetasizer. Pharmacokinetics of clozapine incorporated in solid lipid nanoparticles (SLNs), after intravenous (i.v.) administration to conscious male Wistar rats were studied. The aim of this research was to find out whether the bioavailability of clozapine can be improved by administering clozapine SLN duodenally to rats. Tissue distribution studies of clozapine SLN and suspension were carried out in Swiss albino mice. Average size and zeta potential of SLNs of different lipids with stearylamine ranged from 96.7+/-3.8 to 163.3+/-0.7 nm and 21.3+/-1.3 to 33.2+/-0.6 mV, respectively. AUC((0-infinity)) was increased (up to 2.91-fold) and clearance was decreased (up to 2.93-fold) when clozapine entrapped in SLNs with stearylamine were administered intravenously. Bioavailability of clozapine SLNs were 2.45- to 4.51-fold after intraduodenal administration compared with that of clozapine suspension. In tested organs, the AUC and MRT of clozapine SLNs were higher than those of clozapine suspension especially in brain and reticuloendothelial cell-containing organs. These results indicate that SLN are suitable drug delivery system for the improvement of bioavailability of lipophilic drugs such as clozapine.

Pharmacokinetics and tissue distribution of etoposide delivered in long circulating parenteral emulsion.

PURPOSE: The aim of the study is to ascertain the influence of pegylation of parenteral emulsion (PE) on their long circulating property. METHODS: Etoposide encapsulated parenteral emulsion (EPE) was prepared using soybean oil, egg lecithin and cholesterol. Etoposide encapsulated long circulating parenteral emulsion (PEG-EPE) was prepared using PEG (2000)-DSPE as a stealth agent. The effect of monovalent and divalent electrolytes on the stability of EP was assessed by measuring the fixed aqueous layer thickness (FALT) and flocculation rate. Pharmacokinetics and tissue distribution pattern of PE following i.v. (bolus) were assessed in Wistar rats and Swiss albino mice. RESULTS: FALT of PEG-EPE was larger than that of EPE. In case of PEG-EPE, as the concentration of pegylated lipid (PEG) increased from 0.15 to 0.45% w/v the flocculation rate decreased asymptomatically in the presence of monovalent and divalent electrolytes. The increased circulation time of PEG-EPE (0.3%) after intravenous injection to rats confirms the presence of FALT around globules. PEG-EPE showed improved pharmacokinetic parameters with 5.5 times higher AUC than etoposide commercial formulation (ETP). Tissue distribution results show that etoposide levels in all tissues except in brain and heart were lower in case of PEG-EPE than ETP. The percentage of tumor growth suppression rate (%T/C) in Lewis lung carcinoma bearing mice was 63.23, 62.83 and 33.78% in EPE, PEG-EPE and ETP treated mice, respectively. The improved activity of PEG-EPE is due to enhanced permeability and retention effect (EPR). CONCLUSION: Encapsulation of etoposide in PEG-coated PE produced improved pharmacokinetic profile than that of EPE and ETP.

Preparation, characterization and in vitro release kinetics of clozapine solid lipid nanoparticles.

Clozapine, a lipophilic antipsychotic drug, has very poor oral bioavailability (<27%) due to first pass effect. Solid lipid nanoparticle (SLN) delivery systems of clozapine have been developed using various triglycerides (trimyristin, tripalmitin and tristearin), soylecithin 95%, poloxamer 188 and charge modifier stearylamine. Hot homogenization of melted lipids and aqueous phase followed by ultrasonication at temperature above the melting point of lipid was used to prepare SLN dispersions. Particle size and zeta potential were measured by photon correlation spectroscopy (PCS) using Malvern Zetasizer. Process and formulation variables have been studied and optimized. Differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) studies were performed to characterize state of drug and lipid modification. In vitro release studies were performed in 0.1 N HCl, double-distilled water and phosphate buffer, pH 7.4, using modified Franz diffusion cell. Stable SLN formulations of clozapine having mean size range of 60-380 nm and zeta potential range of -23 to +33 mV were developed. More than 90% clozapine was entrapped in SLN. DSC and PXRD analysis showed that clozapine is dispersed in SLN in an amorphous state. The release pattern of drug is analyzed and found to follow Weibull and Higuchi equations.