K. V. Ramana Murthy

Evaluation of modified gum karaya as carrier for the dissolution enhancement of poorly water-soluble drug nimodipine

Modified gum karaya (MGK), a recently developed excipient was evaluated as carrier for dissolution enhancement of poorly soluble drug, nimodipine (NM). The advantages of MGK over the parent gum karaya (GK) were illustrated by differences in the in vitro dissolution profiles of respective solid mixtures prepared by co-grinding technique. The influence of process variable, such as polysaccharide concentration and method of preparation of solid mixture on dissolution rate was studied. Solubility studies were also performed to explain the differences in dissolution rate. Solid mixtures were characterized by differential scanning calorimetry (DSC), X-ray diffraction studies (XRD) and scanning electron microscopy (SEM). The dissolution rate of NM was increased as the MGK concentration increased and optimum ratio was found to be 1:9 w/w ratio (NM:MGK). It is found that method of preparation of solid mixtures was significantly effected the dissolution rate of NM from solid mixtures. The order of method of preparation in according to their Dissolution Efficiency is physical mixture < co-grinding mixture < swollen carrier mixture < kneading mixture (water as kneading agent) < kneading mixture (70% v/v ethanol as kneading agent) < solid dispersion. Though, the solid mixtures prepared by other methods like solid dispersion, swollen carrier mixture and kneading technique gave faster release, co-grinding mixture prepared in 1:9 w/w ratio (NM:MGK) was found to exhibit a significant improvement in dissolution rate without requiring addition of organic solvents or high temperatures for its preparation and the process is less cumbersome. Hence, co-grinding technique appears to be more easier and the most convenient method from a practical point of view.

Studies on rifampicin release from ethylcellulose coated nonpareil beads

The rifampicin release studies from ethylcellulose coated nonpareil beads were studied. Propylene glycol and Castor oil were used as plasticizers. The in vitro dissolution studies revealed that the release rate is inversely proportional to percent of coating thickness. The release rate also depends on the type of plasticizer used in the coating polymer. The mechanism of drug release follows Higuchi diffusion model. Water vapour permeation studies indicated that the water vapour transport rate through free films is directly related to the drug release rate. DSC thermograms and IR spectras revealed that there is no interaction between rifampicin and other additives. SEM photographs of coated beads, before dissolution and after dissolution, also indicates that the drug release mechanism follows diffusion model.

Nimesulide-Modified Gum Karaya Solid Mixtures: Preparation, Characterization, and Formulation Development

Abstract Solid mixtures of nimesulide (NS) and modified gum karaya (MGK) were prepared to improve the dissolution rate of NS. The effect of drug-carrier ratio on dissolution rate of NS was investigated by preparing the solid mixtures of different ratios by cogrinding method. Solid mixtures were also prepared by physical mixing, kneading, and solid dispersion techniques to study the influence of method of preparation. Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and equilibrium solubility studies were performed to explain the results of in vitro dissolution rate studies. It was clearly evident from the results that the NS dissolution rate was dependent on the concentration of MGK in the solid mixtures, and optimum weight ratio was found to be 1:4 (NS:MGK). Though the dissolution rate of NS from all solid mixtures prepared by different methods improved significantly, maximum improvement in dissolution rate was observed with solid dispersions. The order of methods basing on their effect on dissolution efficiency is solid dispersion>kneading>cogrinding> physical mixing>pure NS. Tablets of pure drug and solid mixtures (1:4 w/w, NS:MGK) were prepared. Though the best results from the dissolution test were obtained for the tablets containing solid dispersions, tablets containing cogrinding mixture were found to be suitable, from a practical point of view, for commercialization.

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

The purpose of this study was to investigate the possibility to develop different levels of correlation between in vitro dissolution parameters and in vivo pharmacokinetic parameters for three rifampicin formulations. A level A correlation of in vitro release and in vivo absorption could be obtained for individual plasma level data by means of the Wagner and Nelson method. Linear correlation could be obtained when percent dose released in vitro was plotted vs percent dose absorbed in vivo with correlation coefficients between 0.954,0.983 and 0.997 for the formulations studied. A second level correlation between mean in vitro dissolution time (MDT) and mean in vivo residence time (MRT) was performed with a correlation coefficient of 0.536,0.420 and 0.335. Finally, it was also possible to establish a good in vitro-in vivo correlation when the T(50%hrs) (time taken to release 50% of rifampicin) in vitro and C(max),T(max) or AUC in vivo were compared.

Relaxor behaviour in certain tungsten bronze ceramics

Abstract Relaxor ferroelectrics with high Curie temperature are attractive candidates for electro-optic and pyroelectric devices. Solid solutions of (Srx Ba1–x)0.8 Na0.4 Nb2O6 where × = 0.3 to 0.6 have been prepared by the conventional ceramic technique. The properties of relaxor ferroelectrics are dependent on ceramic processing conditions. Relaxor characteristics have been studied. A broad transition is observed in all the compositions. The broadness decreases gradually with the increase of strontium concentration.

Chronotherapeutic Drug Delivery Systems - An Approach to Circadian Rhythms Diseases

The purpose of writing this review on chronotherapeutic drug delivery systems (ChrDDs) is to review the literatures with special focus on ChrDDs and the various dosage forms, techniques that are used to target the circadian rhythms (CR) of various diseases. Many functions of the human body vary considerably in a day. ChrDDs refers to a treatment method in which in vivo drug availability is timed to match circadian rhythms of disease in order to optimize therapeutic outcomes and minimize side effects. Several techniques have been developed but not many dosage forms for all the diseases are available in the market. ChrDDs are gaining importance in the field of pharmaceutical technology as these systems reduce dosing frequency, toxicity and deliver the drug that matches the CR of that particular disease when the symptoms are maximum to worse. Finally, the ultimate benefit goes to the patient due the compliance and convenience of the dosage form. Some diseases that follow circadian rhythms include cardiovascular diseases, asthma, arthritis, ulcers, diabetes etc. ChrDDs in the market were also discussed and the current technologies used to formulate were also stated. These technologies include Contin® , Chronotopic®, Pulsincaps®, Ceform®, Timerx®, Oros®, Codas®, Diffucaps®, Egalet®, Tablet in capsule device, Core-in-cup tablet technology. A coated drug-core tablet matrix, A bi-layered tablet, Multiparticulate-based chronotherapeutic drug delivery systems, Chronoset and Controlled release microchips.

Preparation and In Vitro Evaluation of Chitosan Matrices Cross-Linked by Formaldehyde Vapors

Rifampicin-chitosan matrices were prepared by a chemical cross-linking method to develop a sustained-release form. The effects of cross-linking agent (formaldehyde) on the drug release rate and release kinetics were investigated in this study. Moreover, the kinetics of rifampicin released from chitosan matrices exposed to formaldehyde vapors for predetermined time intervals were analyzed using Ritger and Peppas exponential equation. The in vitro release kinetics exhibited a non-Fickian transport model. Increasing the exposure time to formaldehyde vapors decreased the release rate of rifampicin from chitosan matrices as a result of formation of greater structural strength and tighter texture.

Studies on enhancement of dissolution rate of etoposide

Dissolution is the rate-limiting step in the absorption of drugs from solid dosage forms. This is to be focused especially when the drug is poorly soluble. Etoposide is a poorly soluble drug and its absorption is dissolution rate limited. The present study is aimed at improving the dissolution of etoposide. Solid dispersions of drug with surfactants were prepared by using kneading technique. Kneading technique is more applicable to industry. Surfactants such as cetrimide, sodium lauryl sulphate, Tween 80 and Cremophor RH40 were used in different proportions. Etoposide gave faster dissolution rates when Cremophor RH40 was used. The DSC thermograms and IR spectra revealed no interaction of etoposide with these surfactants and no degradation in etoposide molecule was observed.

Nanosuspensions as a versatile carrier based drug delivery system--an overview.

Nanotechnology is being explored in many ways to design a new chemical entity (NCE) to an active pharmaceutical ingredient (API). Of the different nanotechnologies, Nanosuspensions has gained a lot of interest due to its ease of production and applicability to a large number of drugs. This present review article on nanosuspensions is focused on the various principles, production techniques, stability problems, various marketed formulations and current trends associated with the nanosuspensions.

Formulation and Evaluation of Gastro Retentive Floating Drug Delivery System for Propranolol HCl

Asiaticoside is a triterpene obtained from Centella asiatica and demonstrated to have healing potential against various wound models. Wounds are inflicted for constructive reasons even though more often they are results of accidents. This work aims at identifying molecular targets which account for the therapeutic results attributed to the use of asiaticoside. Even though exact mechanisms of action have not been reported, experimental evidences point at the inhibition of pro-inflammation and enhanced tissue regeneration. Keywords: asiaticoside, Centella asiatica , wounds, wound healing