Biomedical subjects

C M Dangor

Publications and source records attributed to C M Dangor.

11 recordsLinked to original sources

PubMed2005

Optimisation and characterisation of bioadhesive controlled release tetracycline microspheres.

A Box-Behnken experimental design was employed to statistically optimise the formulation parameters of a tetracycline microsphere preparation for maximum bioadhesivity and controlled drug release. The quantitative effect of the formulation parameters at different levels on bioadhesion and drug release could be predicted using polynomial equations. A formulation comprising of 3% (w/w) chitosan, 10% (w/w) tetracycline HCl and 9% (w/v) tripolyphosphate was identified for maximising bioadhesivity and obtaining controlled drug release. The optimal microsphere preparation was subsequently characterised in terms of hydration dynamics, release kinetics, antimicrobial activity, thermal properties, morphology and surface pH. Kinetic models revealed that drug release followed Fickian diffusion while textural analysis showed minimal hydration over the test period. Antimicrobial studies showed that the drug concentrations in the in vitro release samples were above the minimum concentration of drug required for inhibition of Staphylococcus aureus growth. Thermal analyses showed a possible interaction between the drug and polymer. Scanning electron microscopy confirmed the integrity of the microspheres and identified the morphological changes following drug release. Surface pH of the microspheres was similar to salivary pH and did not show extremes in changes over the test period.

Adhesiveness↗

PubMed2005

Formulation of rate-modulating pellets for the release of ibuprofen: an extrusion-spheronization process.

PURPOSE: To develop a stable and reproducible modified release pellet formulation containing ibuprofen. METHODS: Using extrusion-spheronization technology to produce pellets. RESULTS: The percentage yield, size distribution and overall pellet shape within the desired size range of 1000-1400 microm was found to be dependent on various process variables. These include extrusion and spheronization speed, spheronization time and composition of the granulation fluid. Formulation factors such as viscosity grade of hydroxypropylmethylcellulose and concentration of microcrystalline cellulose were shown to influence the drug release rate of the pellets. In vitro dissolution studies revealed that the pellets behaved in a pH-dependent manner. Pellets exposed to different drying techniques exhibited an increase in drug release rate in the order corresponding to oven-dried, vacuum-dried, fluid bed-dried and freeze-dried pellets. In conjunction with scanning electron microscopy, kinetic modelling and statistical treatment of dissolution data, it was confirmed that the predominant release rate-controlling mechanism was diffusion, as evidenced from the power law expressions incorporating Fickian and relaxational parameters (M(t) /M(infinity) = K(1)t(n); M(t) /M(infinity) = K(1)t(2n)). Matrix swelling and erosion were not significant factors in modulating the drug release rate. CONCLUSIONS: The pH-dependent property of the pellets may be strategically employed towards development of a site-specific drug delivery system for non-steroidal anti-inflammatory agents. In general, targeting the delivery of an agent with potential for gastric irritation to the proximal intestine/colon may effectively reduce its ulcerogenic effect and ultimately contribute towards improved patient compliance.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1987

Bioavailability of amfepramone hydrochloride sustained release pellets formulation in healthy subjects.

The relative bioavailability and pharmacokinetic profile of two amfepramone (diethylpropion) hydrochloride oral preparations were evaluated in 12 normal volunteers using a newly developed gas-liquid chromatographic procedure to monitor the unchanged drug and its two major metabolites in urine, plasma and saliva. The sustained release pellets formulation (Regenon retard) provided excellent bioavailability and gave broad plateau levels extending over 6 to 8 h after administration, which were intermediate between the "peaks and troughs" shown by the same total dose of the free drug in three equal portions at 4-h intervals.

Adult↗

PubMed1986

Sugar-free liquid pharmaceuticals.

With the reported increased incidence of dental disease in chronically ill children receiving sugar-containing medicines, health care personnel should be made aware of the availability of sucrose-free paediatric preparations. The list of sugar-free liquid preparations for oral use presented will require updating as more products are reformulated to avoid inclusion of fermentable carbohydrates.

Child↗

PubMed1986

Simultaneous determination of amfepramon and its two major metabolites in biological fluids by gas liquid chromatography.

Sensitive and specific procedures based on gas liquid chromatography for the identification, separation and determination of amfepramon (diethylpropion) and its major metabolites ethylaminopropiophenone and diethylnorpseudoephedrine in human plasma, saliva and urine have been described. Acidification of the biological fluid samples has improved the stability of the compounds under conditions of storage.

Biotransformation↗

PubMed1985

Ethanol content of some pharmaceuticals available in the RSA.

The Medicines Control Council is concerned about the influence of the simultaneous ingestion of alcohol and medicines on certain psychomotor functions and the consequent inability of the consumer to perform tasks which require mental clarity. Health care personnel should be aware of the alcohol content of medications when counselling patients receiving drugs against alcoholism or patients who should avoid alcohol. A compilation, short-listed from over 300 ethanol-containing prescription and non-prescription drug products available in the RSA, is presented.

Ethanol↗

PubMedDate not supplied

Effect of formulation variables on in vitro drug release and micromeritic properties of modified release ibuprofen microspheres.

Modified release microspheres of the non-steroidal anti-inflammatory drug, ibuprofen, were formulated and prepared using the emulsion solvent diffusion technique. The contribution of various dispersed phase and continuous phase formulation factors on in vitro drug release and micromeritic characteristics of microspheres was examined. The results demonstrated that the use of Eudragit RS 100 and Eudragit RL 100 as embedding polymers modified the drug release properties as a function of polymer type and concentration. Eudragit RS 100 retarded ibuprofen release from the microspheres to a greater extent than Eudragit RL 100. The drug/polymer concentration of the dispersed phase influenced the particle size and drug release properties of the formed microspheres. It was found that the presence of emulsifier was essential for microsphere formation. Increasing the concentration of emulsifier, sucrose fatty acid ester F-70, decreased the particle size which contributed to increased drug release properties. Scanning electron microscopy revealed profound distortion in both the shape and surface morphology of the microspheres with the use of magnesium stearate as added emulsifier. The application of an additional Eudragit RS 100 coat onto formed microspheres using fluid bed technology was successful and modulated the drug release properties of the coated microspheres.

Delayed-Action Preparations↗

PubMedDate not supplied

In vitro characterization of a controlled-release chlorpheniramine maleate delivery system prepared by the air-suspension technique.

Non-pareil cores were spray-coated with a chlorpheniramine maleate (an alkylamine antihistamine) layer and a Eudragit NE30D overcoat in a Wurster air-suspension apparatus. In vitro dissolution studies demonstrated that drug release was a function of polymer membrane thickness. Polyethylene glycol 6000, as a hydrophillic additive, increased the in vitro release of chlorpheniramine maleate from the pellets. Pellets coated with 8.30% Eudragit NE30D, 0.50% talc and 1.00% polyethylene glycol 6000 were found to display desirable controlled release characteristics for chlorpheniramine maleate over the 8-h testing period, which were also comparable with that of Dykatuss capsules. The controlled release pellets exhibited first-order release characteristics for chlorpheniramine maleate. Reproducibility of the manufacturing conditions employed in the study were confirmed thus ensuring reproducibility of drug release characteristics between batches of chlorpheniramine maleate pellets. Drug release from the pellets was shown to be independent of the dissolution method and medium used. Pellets displayed no significant change in drug release characteristics relative to the initial drug release data when stored for 12 weeks at room temperature (20 +/- 2 degrees C) and for 8 weeks at a low temperature (5 +/- 1 degrees C). However, pellets stored at 37 degrees C with 80% relative humidity and at 40 +/- 2 degrees C showed a slower in vitro drug release after 8-week storage and therefore failed to maintain their initial drug release profile.

Capsules↗

PubMedDate not supplied

Formulation and preparation of controlled release pellets of salbutamol by the air suspension technique.

A controlled release preparation of salbutamol may improve patient compliance, minimise side effects and be valuable in the treatment of nocturnal asthma by extending drug action throughout the night. The aim of the study was therefore to formulate a controlled release pellet preparation of salbutamol via the air suspension technique. The study established that curing for 24 h at 38 +/- 0.5 degrees C was necessary for homogeneous film coats of Eudragit RS30D and hence stable drug release characteristics. Pellets coated with 6% Eudragit RS30D (polymer), 12.5% triethyl citrate (plasticiser) and 0.5% magnesium stearate (antitackiness agent) displayed desirable controlled drug release characteristics over the 8 h testing period. The manufacturing conditions employed in the study were shown to be reproducible thus ensuring reproducibility of drug release characteristics between batches of salbutamol controlled release pellets. Short term stability testing on the newly formulated pellets indicated no significant change in drug release characteristics relative to the initial drug release data when stored for 8 weeks at room temperature 20 +/- 2 degrees C or 37 degrees C with 80% Relative Humidity or at low temperature (5 +/- 1 degrees C). However, pellets stored at 40 degrees C showed a slower in-vitro drug release after 8 weeks of storage and therefore failed to maintain their initial drug release profile.

Adrenergic beta-Agonists↗

PubMedDate not supplied

Microencapsulated Eudragit RS30D-coated controlled-release pellets: the influence of dissolution variables and topographical evaluation.

The air suspension technique was employed to prepare Eudragit RS30D-coated controlled-release pellets of salbutamol. Drug release in dissolution studies can be dependent on the dissolution method and medium used. Thus, the aim of this study was to investigate the influence of various dissolution methods and dissolution medium pH values on drug release from a batch of pellets which displayed controlled drug-release characteristics over an 8-h period in deionized water using the rotating basket method. In vitro testing using the official USP XXII (rotating basket and rotating paddle) and non-official (rotating bottle) methods showed drug release to be independent of the method used. The prepared pellets displayed pH-dependent drug-release characteristics when tested in hydrochloric acid (pH 1.5), phosphate buffer (pH 6.8) and deionized water (pH 7.2). Also, in vitro testing, which exposed the pellets to a changing pH gradient that simulated the gastrointestinal pH conditions following oral administration, was used to confirm the drug-release characteristics. The results showed controlled-release characteristics to be maintained, with the drug being released over an 8-h period. Scanning electron microscopic evaluation proved useful in the elucidation of the physical characteristics of the controlled-release pellets as well as in the identification of a possible mode of drug transfer into the dissolution medium.

Acrylic Resins↗

PubMedDate not supplied

Ionotropic gelation: encapsulation of indomethacin in calcium alginate gel discs.

Ionotropic gelation by divalent metal interaction was employed as an approach to design a modified release multiple-unit oral drug-delivery system. This process was achieved by crosslinking an indomethacin-sodium alginate dispersion with calcium ions to induce the spontaneous formation of indomethacin-calcium alginate gel discs. A significant part in the validation of the integrity of the system, involved a preformulatory stage for the optimization of the curing conditions and potency determination of the gel discs. A three-phase approach was developed to establish the critical curing parameters. Since curing involved crosslinking of the sodium alginate with calcium ions, an optimal concentration of calcium chloride (phase one) and crosslinking reaction-time (phase two) had to be determined. Furthermore, the third phase involved the optimization of the air-drying time of the gel discs. In phases one and two, stabilization of in vitro drug-release characteristics was used as the marker of optimal crosslinking efficiency. Phase three was based on achieving fully dried gel discs by drying to constant weight at 21 degrees C under an extractor. The study revealed that optimal crosslinking efficiency was achieved in 1%w/v calcium chloride solution for 24 h and air-dried at 21 degrees C under an extractor for 48 h. The three solvent/solution systems investigated for their ability to liberate completely the drug from the matrix system were methanol, sodium citrate (1%w/v) and phosphate buffer pH 6.2. Phosphate buffer provided optimal drug removal, in addition to its ability to induce swelling of the calcium alginate gel discs. Furthermore, drug loading also increased with the use of increasing concentrations of sodium alginate in the formulations.

Administration, Oral↗