Ethylcellulose microcapsules containing theophylline were prepared by the phase-separation coacervation process induced by non-solvent addition in the presence of variable amounts of polyisobutylene. No statistical difference was evident between the different sized microcapsules with respect to their drug content, wall thickness and in-vitro drug dissolution profiles. Poly-isobutylene was, however, found to influence the release profiles of drug to a great extent. An increase in polyisoburylene concentration retarded the release of theophylline from the microcapsules due to the formation of smaller and spheroidal coacervate droplets in larger volumes, which resulted in the formation of more evenly coated microcapsules. Although the release of theophylline from the microcapsules was found to fit both the first order and diffusion controlled release processes, differential rate treatment indicated that the overall release, in fact, was governed by diffusion controlled process.

Capsules↗

PubMedDate not supplied

Captopril renography for the detection of renovascular hypertension. A preliminary report.

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Adult↗

PubMedDate not supplied

Statistical optimization of transdermal drug delivery system of terbutaline sulfate by factorial analysis.

A matrix type of transdermal drug delivery system of terbutaline sulfate was designed and developed by full 3(2) factorial method using polyvinyl alcohol (PVA) of medium molecular weight and polyvinyl pyrrolidone (PVP K-30) as matrix forming polymer and propylene glycol as plasticizer. Patches were designed to deliver 62 micrograms/cm2/hr of the drug into the systemic circulation. These were evaluated for in vitro skin permeation study through excised guinea pig skin. The permeation followed Higuchi kinetics, as its coefficients of correlation (r = 0.965-0.978) predominates over other permeation kinetics. Various physico-chemical parameters of the patches were investigated. Statistical optimization of in vitro permeation rate of the drug from the films were evaluated using two way analysis of variance (ANOVA), regression analysis.

Administration, Cutaneous↗

PubMedDate not supplied

Assessment of bioavailability of experimental controlled release microcapsules of nifedipine.

Experimental controlled release nifedipine microcapsules composed of ethylcellulose and eudragit RL were explored for the assessment of bioavailability on rabbit. The pharmacokinetic parameters were compared between the formulations and with the pure drug material. A statistically significant difference between the formulations was noticed in the parameters, K, T1/2, AUC (0-->infinity), MRT and bioavailability but not in Vd, Cmax and Tmax and in each case a highly significant difference was observed with reference drug material. Controlled release absorption profiles in vivo were observed from the experimental microcapsules as revealed by the Wagner-Nelson method. The absorption lag time, absorption rate constant, and absorption half life were calculated by using the back projection method of residuals. A good correlation demonstrated between in vivo absorption and in vitro release data for both the products merits specific attention. There was no loss in bioavailability of the experimental ethylcellulose microcapsule (drug content 75.8%), even though nifedipine undergoes extensive first pass metabolism.

Animals↗

PubMedDate not supplied

Computer supported studies on design and evaluation of solid dispersions of carbamazepine.

The main advantages of solid dispersions (the drug could be maintained in a bioavailable form, dosage reduction and cleaner manufacturing conditions) provide scope for the continued interest in field. Additionally, their use in providing a sustained or controlled release of drugs has only been tentatively examined. In the present study, Carbamazepine has been used to develop a dosage form which will provide a booster amount followed by sustained release of the drug for effective control of epileptic seizures while keeping the serum level of the drug at minimum. Enteric polymers CAP and CAT have been used to retard the release till the formulation reaches the intestine. Either individually or combined fractions of the formulations may be used in the therapy of epilepsy.

Anticonvulsants↗

PubMedDate not supplied

Design and evaluation of microcapsules of diltiazem hydrochloride.

Diltiazem Hydrochloride (DTZ.HCl), a potent calcium channel blocker was microencapsulated by emulsion/solvent evaporation technique using non-aqueous solution of Ethylcellulose (EC) polymer to achieve its release from microcapsules at a slower rate. At the optimal conditions of process variables such as stirring speed, temperature of the medium, drug-polymer ratio, maximum encapsulation efficiency was obtained and the microcapsules produced were free flowing, discrete and spherical as evident from Scanning Electron Microscopy. The in vitro release experiments were carried out in the simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 7.2 phosphate buffer) using USP XXII apparatus II. The data obtained from the dissolution profiles were compared in the light of different kinetic models and the regression coefficients were compared.

Capsules↗

PubMedDate not supplied

Preparation and in vitro dissolution of isoniazid from ethylcellulose microcapsules.

Microcapsules of isoniazid were prepared by phase separation coacervation process induced by non-solvent addition and using ethylcellulose (EC) as coating polymer. When polyisobutylene (PIB)--a protective colloid was present at sufficient concentration, film coated drug particles were formed. At 0-6% PIB concentration, the microcapsules were aggregated. Increase of colloid concentration produced microcapsules of less aggregation and higher drug content because coating became progressively thinner. PIB concentration also controlled the particle size and the release rate of drug from microcapsules. Wall thickness and EC loss were calculated from drug content. Microcapsules coated with EC were prepared with 7-9% PIB. Scanning Electron Microscopy was used to study the nature of aggregation and coating behaviour. The in vitro dissolution study confirmed the first order release pattern and also the Higuchi Matrix model.

Antitubercular Agents↗

PubMedDate not supplied

Product development studies for stabilization of oral liquid enzyme preparations containing diastase and papain.

A product development study was undertaken with a view to stabilize acid sensitive amylolytic enzyme diastase and alkali sensitive proteolytic enzyme papain. An unique high technology method was adopted for both enzymes with enteric coating and non-enteric film forming materials respectively to achieve site specificity of action, better stability and to protect diastase from the adverse acid pH of the stomach. Feasibility of incorporating various excipients like thickening agents, surfactants, preservatives, etc., to produce stable elegant oral liquid suspension was also studied. Release studies of the enzymes both in simulated gastric and simulated intestinal juices showed steady and consistent release. The proteolytic and amylolytic activities were assessed by standard pharmacopoeial methods. The stability of the product during the studies was satisfactory. Reduction in addition of overages of costly enzymes met the project technically feasible and economically viable.

Amylases↗