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Results for “drug delivery systems”

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At least 19 recordsLinked to original sources
PubMed1979

Placebo granules as cores for timed release drug delivery systems.

A drug delivery system is proposed constituted of spherical placebo granules as cores with polymeric surface films containing drug. This timed release dosage form has been prepared by means of a fluidized bed coating technique using ethyl cellulose as the polymeric film and caffeine and salicylic acid as model drugs. The release of the drugs from the dosage form (a) at different drug concentrations and (b) into solutions of different pH showed that drug release was linearly related to the square root of time. Good agreement was found between the theoretical release rate of caffeine, calculated according to Higuchi's equation for a homogenous matrix using membrane permeation parameters measured on linear films, and the experimental results in the case of low drug concentrations. Deviation of the release rate from the homogenous model at high drug concentrations could be explained by crystallization of the drug from the film.

Caffeine↗
PubMed1977

Analysis of theoretical behavior of a proposed zero-order drug delivery system.

An analysis of the theoretical behavior of a proposed zero-order drug delivery system is presented. Equations describing drug release with time are developed using a physically realistic model. The theory agrees well with experimental data and indicates that drug release from the device is nearly, although not rigorously, zero order.

Delayed-Action Preparations↗
PubMed1977

Dosage form index: an objective criterion for evaluation of controlled-release drug delivery systems.

A dimensionless parameter, the dosage form index (DLtau) is proposed for evaluating the performance of drug delivery systems. The index is defined as the ratio of the maximum to minimum concentrations of the drug in plasma within each interdose interval (in hours), tau, during repetitive administration of the dosage form in the quasisteady state. Dosage form indexes can be averaged among subjects or within subjects at successive time periods to arrive at a mean value. As an example, two GI therapeutic systems--the 15- and 20-mg/hr acetazolamide systems that deliver drug at constant rates for 6 and 12 hr and contain 125 and 250 mg, respectively--were compared in normal subjects with a commercial sustained-release product containing 500 mg of acetazolamide. The dosage form index, DI24, was 4.9 for the sustained-release dosage form and 3.2 for the 20-mg/hr system; DI12 was 1.6 for the 15-mg/hr system.

Acetazolamide↗
PubMed1976

Testing of drug delivery systems for use in the treatment of narcotic addiction.

The evaluation of the drug release characteristic of four naltrexone delivery systems has been carried out together with the development of analytical techniques and an investigation of the metabolic profile of naltrexone. Pharmacologic evaluation of the four delivery systems in the mouse indicated significant analgesic antagonism for a period of from 16-22 days. Further evaluation of one of these systems by measurement of the rate of excretion of radioactivity after administration of radiolabelled naltrexone in the delivery system confirmed that significant release occurs for a time period of about 15 days. Electron capture gas-liquid chromatographic assays for naltrexone and naloxone in plasma or urine have been developed that yield linear calibration curves and are sensitive to one ng/ml. Studies on naltrexone disposition indicate that (a) binding to plasma proteins in several species varies from 20-26%, (b) distribution of drug from blood is extremely rapid and extensive, (c) beta-naltrexol is a major metabolite of naltrexone in man, monkey and guinea pig among six species studies, whereas alpha-naltrexol is a minor metabolite in the monkey and guinea pig only, and (d) metabolic reduction of naltrexone occurs in the 100,000 x g supernatant of guinea pig liver. Pharmacokinetic studies of naltrexone in the dog and monkey indicate that the drug is rapidly distributed and eliminated, has a very large apparent volume of distribution and a total body clearance greater than the rate of liver blood flow.

Animals↗
PubMed1975

Testing of drug delivery systems for use in the treatment of narcotic addiction.

The evaluation of the drug release characteristic of four naltrexone delivery systems has been carried out together with the development of analytical techniques and an investigation of the metabolic profile of naltrexone. Pharmacologic evaluation of the four delivery systems in the mouse indicated significant analgesic antagonism for a period of from 16-22 days. Further evaluation of one of these systems by measurement of the rate of excretion of radioactivity after administration of radiolabelled naltrexone in the delivery system confirmed that significant release occurs for a time period of about 15 days. Electron capture gas-liquid chromatographic assays for naltrexone and naloxone in plasma or urine have been developed that yield linear calibration curves and are sensitive to one ng/ml. Studies on naltrexone disposition indicate that (a) binding to plasma proteins in several species varies from 20-26 per cent, (b) distribution of drug from blood is extremely rapid and extensive, (c) beta-naltrexol is a major metabolite of naltrexone in man, monkey and guinea pig among six species studied, whereas alpha-naltrexol is a minor metabolite in the monkey and guinea pig only, and (d) metabolic reduction of naltrexone occurs in the 100,000 x g supernatant of guinea pig liver. Pharmacokinetic studies of naltrexone in the dog and monkey indicate that the drug is rapidly distributed and eliminated, has a very large apparent volume of distribution and a total body clearance greater than the rate of liver blood flow.

Animals↗
PubMed1977

Zero-order drug delivery system: theory and preliminary testing.

A new approach to zero-order drug delivery that includes geometric factors is described. An experimental device based on the theory was tested by following the release of stearic acid into ethanol. Three separate trials indicated that the solid was released via a zero-order process in a reproducible manner.

Delayed-Action Preparations↗
PubMed1976

The role of drug delivery systems in cancer chemotherapy.

One approach to effective cancer chemotherapy is to maximize the exposure of tumor cells to cytotoxic drugs while minimizing the exposure of sensitive normal cells to such agents. This implies the need for control of the pharmacodynamics of anti-tumor drugs in terms of blood clearance kinetics, disposition in tissues, passage across membrane barriers, and interaction with metabolic pathways. A promising approach to pharmacodynamic control is the microencapsulation of drugs within liposomes. The clearance kinetics and tissue disposition of the drug is then dictated by the pharmacokinetic behavior of the liposomal carrier. The blood clearance rates and tissue uptake of liposomes themselves depend upon physical characteristics such as particle size and surface charge. It is also possible to promote specific interaction between cells and liposomes in vitro by preparing liposomes containing biological macromolecules such as lectin receptors. The potentialities of microencapsulation as an adjunct to chemotherapy are discussed.

Animals↗
PubMed1979

Sustained drug delivery systems. I. The permeability of poly(epsilon-caprolactone), poly(DL-lactic acid), and their copolymers.

The maximum steady state flux, diffusion coefficients, and solubilities of five contraceptive steroids in homopolymers and copolymers of epsilon-caprolactone and DL-lactic acid were determined. The permeabilities of polymers of epsilon-caprolactone were comparable to silicone rubber and, by inference, are suitable for the construction of drug delivery devices. Poly(DL-lactic acid) was 10(4) times less permeable, although its permeability was significantly enhanced by additives.

Delayed-Action Preparations↗
PubMed1976

[Measurements of intraocular gentamicin concentration using hydrophilic contact lenses as drug delivery system (author's transl)].

Investigations were performed with two groups of anaesthetised rabbits to test the possibility of increasing the penetration of topically administered. Gentamicin into the eye through the use of hydrophilic contact lenses. After application of Gentamicin drops the drug concentration in the aqueous humour was biologically quantitated. In the first group one eye of the animal was fitted with a hydrophilic contact lens and the other eye was submitted to a comparative measurement. In the second group both eyes were fitted with contact lenses which had been soaked in Gentamicin solutions of two different con-entrations. The result showed an increased intraocular Gentamicin level in the eyes fitted with hydrophilic contact lenses. However, in the latter group we found low intraocular drug levels where only contact lenses soaked in Gentamicin solution were used.

Absorption↗
PubMed1979

Sustained drug delivery systems II: Factors affecting release rates from poly(epsilon-caprolactone) and related biodegradable polyesters.

The release rates of several steroids from films and capsules of homopolymers and copolymer of epsilon-caprolactone, DL-lactic acid, and glycolic acid were measured in vitro and in vivo for up to 200 days. Relatively constant release rates from capsules (reservoir devices) were observed only under certain conditions. Factors that influence the drug release kinetics were evaluated. Release from poly(epsilon-caprolactone) and poly(epsilon-caprolactone-co-DL-lactic acid) was diffusion controlled. Release from poly(DL-lactic acid-co-glycolic acid) was associated with polymer degradation. Release from poly(DL-lactic acid) was very slow when diffusion controlled.

Crystallization↗
PubMed1978

Soluble gentamicin ophthalmic inserts as a drug delivery system.

A comparison was made of soluble 14C-gentamicin ophthalmic inserts with drop, ointment, and the subconjunctival routes of administration. The insert is a solid, solubilizable collagen polymer containing 14C-gentamicin. We compared the levels of 14C-gentamicin in the rabbit tear film and in multiple corneal and scleral biopsies to determine which route of administration gave the best results. The wafer route of administration gave the highest tear film and tissue concentration of drug. The tear film concentration by subconjunctival injection was surprisingly low. Soluble collagen inserts offer a new method of delivering high doses of gentamicin in infected corneal tissue in a convenient and atraumatic fashion.

Administration, Topical↗
PubMed1975

Oral absorption efficiency of acid-labile antibiotics from lipid-drug delivery systems.

The utility of cholesterol, cholesteryl acetate, and beta-sitosterol in protecting and improving the oral absorption efficiency of acid-labile antibiotics is discussed. The potassium salts of penicillin G and penicillin V and erythromycin lactobionate were studied. The stability of the two penicillins in simulated gastric fluid was determined iodometrically. The rank order of acid protective activity was: cholesteryl acetate greater than beta-sitosterol greater than cholesterol. Oral administration of erythromycin lactobionate coated with cholesteryl acetate produced a twofold increase in human urinary excretion of erythromycin when compared with the uncoated material. Potassium salts of penicillin G and penicillin V coated with cholesteryl acetate yielded 1.6- and 2-fold higher urine levels, respectively, as compared with the uncoated candidates.

Absorption↗
PubMed1977

Bioavailability and activity of topical corticosteroids from a novel drug delivery system, the aerosol quick-break foam.

Experiments were conducted to: (a) compare the bioavailability of betamethasone benzoate in a quick-break aerosol foam and semisolid dosage forms, (b) compare the activity of betamethasone benzoate, betamethasone valerate, clobetasol propionate, triamcinolone acetonide, desonide, flumethasoid reservoir formation in skin, and (d) assess the effect of a natural moisturizer. Efficacy was determined by a graded response 6-hr occluded vasoconstriction test with subsequent reocclusion for reservoir demonstration. Moisturizer effect was assessed by a nonoccluded vasoconstriction test using "plain" and sodium 2-pyrrolidone-5-carboxylate-containing concentrates on arms pretreated with water or moisturizer. The activities of betamethasone benzoate concentrate, collapsed foam, ointment, and gel were similar and significantly better than the activity of the cream. Clobetasol propionate was significantly better than the other medicated concentrates, which were equivalent. Steroid-induced blanching decreased in the presence of a moisturizer.

Administration, Topical↗