Anomalous behavior of some hydroflumethiazide crystal samples.
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Crystallization↗
Biomedical subjects
O I Corrigan
Publications and source records attributed to O I Corrigan.
In vitro evaluation of physiological availability of aspirin tablets.
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Aspirin↗
Characterization of drug release from diltiazem-loaded polylactide microspheres prepared using sodium caseinate and whey protein as emulsifying agents.
The influence of milk protein emulsifying agents on the characteristics, particularly drug release, of polylactide microspheres was investigated. Diltiazem loaded polylactide (PL) microspheres were successfully prepared using the dairy proteins, sodium casinate (SC) and whey protein isolate (WPI) as the emulsifying agents. Microspheres were characerized in terms of microsphere yield, electron microscopy, particle size, drug loading, DSC and XRD analysis and drug release. The yields of microspheres obtained were 53-63% and were independent of the emulsifying agent used. SEM revealed that, regardless of the emulsifying agent employed, the microspheres were of good sphericity, but the surface appearance of the microspheres was not the same in all cases. The milk proteins resulted in microspheres approximately half the size of those obtained with methylcellulose (MC). Significant differences in drug loading were observed between the three emulgents, the MC systems giving the highest values. Release profiles were sigmoidal in shape and were well fitted to the equation ln (x/1 - x) = k x t - k x tmax, reflecting degradation controlled drug release. The parameter k increased with drug loading, while tmax decreased. The relationships between the release parameters [P(k and tmax)] and loading (L) could be quantified by equations of the form P = a x L(N), N being negative in the case of tmax. Apart from the effect on loading efficiency, neither SC nor WPI appeared to significantly alter drug release. The quantitative relationships observed in this study may have more general application in quantifying drug release from drug-polymer composites at low loadings where polymer degradation controls drug release.
Calorimetry, Differential Scanning↗
Impact of a nationwide limited prescribing list: preliminary findings.
In the Republic of Ireland, the state pays the cost of medical care for around 40 percent of the population through the General Medical Services (GMS). Doctors treating GMS patients are entitled to prescribe from an approved list of drugs. In October 1982, many antacids, cough and cold preparations, antihistamines, and mild analgesics were removed from the GMS prescribing list. The visiting rate and the amount of prescribing fell in the GMS during 1982-83. Drug utilization within the GMS was measured using prescription numbers and in the total population using data obtained from pharmaceutical wholesalers expressed as defined daily doses. These results showed substantial changes in GMS prescribing in the utilization of mefenamic acid, carbocysteine, and H2-receptor antagonists associated with the introduction of the limited list, suggesting a switch to these agents from delisted preparations. The therapeutic and economic implications of this policy are discussed.
Drug Prescriptions↗
Release kinetics of fluphenazine from biodegradable microspheres.
Fluphenazine-loaded microspheres were prepared using biodegradable lactide and lactide-co-glycolide polymers. Sustained release of fluphenazine was achieved with fluphenazine loadings of up to 30 per cent in both the lactide and lactide-co-glycolide polymers. Fluphenazine release from microspheres was found to increase with increasing drug loading and was most rapid from the poly-L-lactide-co-glycolide microspheres. The release profiles showed a 'lag' period followed by an accelerating release phase and in some cases a decay period, i.e. the release profiles were sigmoidal and fitted the Prout-Tomkins equation (Prout and Tompkins 1944). Consequently it was considered that polymer degradation, the primary rate-determining step controlling drug release, occurred by a mechanism involving propagation of active sites, drug release reflecting the spread of this degradation throughout the polymer.
Biodegradation, Environmental↗
In vitro analysis of the release of incorporated agents from sodium caseinate microspheres.
Drug loaded microspheres were successfully prepared using the dairy protein, sodium caseinate (SC), as the carrier material and containing hydrochlorothiazide, eosin, patent blue violet and sodium salicylate. The morphology of the microspheres varied depending on the incorporated material. Release of the incorporated agents from these systems was rapid with over 90% release in each case within 1 h. Further drug release occurred at a greatly reduced rate with a certain proportion of the drug loading appearing to be indefinitely entrapped within some of the microspheres. The drug release profiles were poorly described using the square root of time and Sinclair and Peppas equations but were well described by a biexponential equation. Analysis of the parameter estimates from the biexponential equation indicated that the initial rapid release phase was essentially completed within 5 min for all but the eosin microsphere systems and this timeframe was of the same order of magnitude as that found for the initial swelling of these microsphere systems as analysed by swelling studies using optical microscopy. Considering both the swelling study and the results from the release experiments, it seems likely that addition of SC microspheres to aqueous media results in immediate hydration and swelling. This process facilitates the rapid diffusional passage of water soluble drugs through the swollen and hydrated microsphere matrix, with drug release occurring almost unhindered unless other factors favour the retention of the incorporated agent with the microsphere.
Caseins↗
Preparation and evaluation of microspheres prepared from whey protein isolate.
Whey protein (WPI) microspheres were successfully produced containing hydrochlorothiazide, eosin, patent blue violet and sodium salicylate using a w/o emulsification method with glutaraldehyde cross linking. The release of these compounds from WPI microspheres occurred rapidly, with at least 70% of the incorporated material released for all systems within the first 20 min. Release of microsphere payload was essentially complete within 1 h. The degree of glutaraldehyde cross-linking was found to have no effect on the release profile for durations of cross-linking up to 24 h. Of a range of release equations examined, the experimental release data was best described by a biexponential equation and this agrees with the work of Tomlinson et al. (1984) for the release of drugs from albumin microspheres. Swelling of the microsphere systems was examined as this may contribute to the rapid release of drug from these systems.
Chemical Phenomena↗