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Biomedical subjects

M S Roberts

Publications and source records attributed to M S Roberts.

At least 253 records · Page 14Linked to original sources
PubMed1981

Determination of therapeutic plasma concentrations of tetrabenazine and an active metabolite by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method for the determination of tetrabenazine and a hydroxy metabolite in plasma is described. Tetrabenazine and the hydroxy metabolite are quantified as their dehydro derivatives using fluorescence detection. This method has been applied to the analysis of plasma samples from patients with Huntington's chorea and has been found to be sensitive, reliable and specific for tetrabenazine and the hydroxy metabolite. The plasma concentrations of tetrabenazine found in patients were lower than could be detected using previously published methods.

Chromatography, High Pressure Liquid↗
PubMed1981

Availability of isosorbide dinitrate, diazepam and chlormethiazole, from i.v. delivery systems.

The loss of isosorbide dinitrate from aqueous solutions stored in plastic infusion bags and/or infused through plastic giving sets was investigated. During simulated infusions, the loss of isosorbide dinitrate was found to be flow-rate dependent. The clinical and pharmacokinetic significance of this loss is discussed. Infusion o isosorbide dinitrate from a glass syringe through high density polyethylene tubing overcame the loss associated with its administration via plastic infusion bags and intravenous giving sets. This method was also applied successfully to minimise the previously reported loss of diazepam and chlormethiazole during infusions.

Adsorption↗
PubMed1981

Pharmacists' tasks, skills and attributes. Their professional importance and desirable teaching environment in the Australian state of Tasmania.

The professional importance of tasks, skills and attributes of pharmacists in an Australian state have been evaluated by various groups of pharmacists and allied health professionals. The most desirable teaching environment (academic or workplace) for the teaching of these tasks and skills has also been determined. Essential tasks, skills and attributes include those on drug knowledge, prescription handling and bench skills, verbal skills and professional responsibility. Most pharmacists' tasks and skills should be taught in both the academic environment and the workplace.

Allied Health Personnel↗
PubMed1981

Interactions between drugs and polyvinyl chloride infusion bags.

Forty-six injectable drug products, many of which are administered by i.v. infusion, were studied for loss from aqueous solutions stored in polyvinyl chloride infusion bags for various periods of time. The polyvinyl bags were stored in the dark at room temperature for up to three months. Drugs stored in glass vials served as controls. The solutions were assayed spectrophotometrically at regular intervals. The effects of drug concentration and pH on the loss of drug from solution were studied. Octanol-water partition coefficients were used as a gauge of lipid solubility of the drugs. Five of the drug products-clomethiazole edisylate, diazepam, hydralazine hydrochloride, thiopental sodium, and warfarin sodium-were found to be lost to a substantial extent after one week. For all drugs studied, the effects of the initial concentration on drug loss varied. The amount of drug lost over a given time was a function of the pH of the solution. The main physico-chemical determinants controlling drug sorption appeared to be the extent of ionization and the lipid solubility of the drug. For most of the drugs studied, minimal losses from the aqueous solutions were observed over short periods of storage time. Disappearance was slow and time dependent, indicating a diffusion-controlled sorption process. The losses of clomethiazole edisylate, thiopental sodium, and diazepam may be clinically important.

Drug Packaging↗
PubMed1980

Effect of posture and sleep on pharmacokinetics. I. Amoxycillin.

The pharmacokinetics of amoxycillin in normal male volunteers was studied during the states of bedrest, sleep and ambulation. The absorption and disposition of amoxycillin in ambulatory subjects was found to be comparable to that reported previously by other workers. Serum amoxycillin concentrations were found to be significantly greater during ambulation than during bedrest and sleep. The difference in serum levels resulted from an increased apparent total serum clearance and amoxycillin renal clearance during bedrest and sleep compared to ambulation. No significant differences in the clearance was found between the states of bedrest and sleep. The change in renal clearance of amoxycillin during ambulation was attributed to a diminished renal blood flow. Although the terminal half-life of amoxycillin did not differ significantly, the apparent volume of distribution appears to be much greater during bedrest and sleep than during ambulation. This difference could be explained pharmacokinetically using a two compartment model. No significant difference was found between the rates of absorption of amoxycillin as reflected by the lag time and time to peak serum amoxycillin. The actual values for these parameters would suggest, however, that the absorption of amoxycillin is faster during ambulation than in bedrest and that the absorption rate during sleep is slowest. The clinical implications of the effect of posture and sleep on the pharmacokinetics of amoxycillin are discussed.

Adult↗
PubMed1980

Metabolism of salicylate during chronic aspirin therapy.

1. The effects of chronic administration of aspirin in therapeutic doses (3.9 g/day) on plasma and salivary salicylate levels were studied in eight subjects. 2. The urinary excretion profile for free salicylic acid and metabolites of salicylate were examined. 3. Plasma and salivary salicylate levels declined significantly after peak levels were achieved between days 3 and 10. 4. The decline in plasma and salivary salicylate levels may be due to an induction of a metabolic pathway such as salicylurate formation (Furst, Gupta & Paulus, 1977). Only the mean fraction of salicylate excreted as salicylurate appears to increase with time during the present study, although the change was not significant statistically. 5. The decline in plasma and salivary salicylate levels during chronic therapy may lead to an apparent 'tolerance' of some rheumatoid patients to aspirin.

Arthritis, Rheumatoid↗
PubMed1980

The availability of nitroglycerin from parenteral solutions.

The availability of nitroglycerin from solution infused from Viaflex plastic infusion bags or glass infusion bottles through Buretrol plastic giving sets has been examined. Each of the individual components of the infusion bag/giving set system (i.e. infusion bag, burette and infusion tubing) sorbed nitroglycerin to a significant extent. It was found that the event and rate of nitroglycerin disappearance from solutions stored in each of the components were in the rank order: tubing greater than burette greater than infusion bag. The disappearance kinetics of nitroglycerin from solutions stored in each component was more accurately described by a 'diffusion' model than by the 'two compartment kinetic' model reported previously. The dimensions of the components and the volume of solution used were determinants of the rate and extent of nitroglycerin disappearance. In simulated infusions of nitroglycerin through plastic infusion bag (or glass bottle)/giving set system the flow rate of solution through the plastic infusion tubing affected the concentration of nitroglycerin in the effluent and the extent of sorption by the components of the infusion delivery system. The loss of nitroglycerin in these studies could be accounted for solely by the sorption of nitroglycerin by the plastic components of the infusion bag/giving set system.

Biological Availability↗
PubMed1978

Loss of nitroglycerin from intravenous infusion sets.

During initial studies with nitroglycerin infusion in patients with acute myocardial infarction, higher doses than previously reported were required to achieve the desired haemodynamic effect. A flow-rate-dependent loss of drug from the plastic infusion set was demonstrated during simulated infusion. This loss was considerably reduced when nitroglycerin was infused from glass syringes through high-density polyethylene tubing.

Acute Disease↗
PubMed1978

Effect of repeated skin application on percutaneous absorption of salicylic acid.

Various concentrations of salicylic acid in hydrophilic ointment were applied repeatedly at daily or weekly intervals to rats in vivo. Salicylic acid absorption through treated skin was monitored by determining the penetration fluxes of salicylic acid through skin excised at various times. A gradual decrease in the salicylic acid penetration flux was observed following weekly applications of either 5 or 10% salicylic acid in hydrophilic ointment. The penetration flux of 1% salicylic acid remained constant. In the daily applications of 5 and 10% salicylic acid, the penetration flux increased after approximately 2 days of treatment and declined thereafter. The penetration flux of salicylic acid from the 1% salicylic acid increased slightly after 3--4 days of treatment.

Administration, Topical↗
PubMed1978

The percutaneous absorption of phenolic compounds: the mechanism of diffusion across the stratum corneum.

The effect of temperature on the permeation of phenolic compounds from aqueous solution through excised human skin has been examined. From a thermodynamic analysis of the data, a mechanism is postulated by which these solutes penetrate through human skin. For the more polar solutes it is suggested that the main resistance to penetration is the lipid barriers in the stratum corneum. Diffusion of these substances through the stratum corneum appears to depend on the breaking of hydrogen bonds in the desolvation of the solute during this penetration process and by the overall 'viscosity' of the stratum corneum. With non-polar solutes, the aqueous boundary layers appear to provide an additional barrier to the penetration of phenolic compounds.

Chemical Phenomena↗
PubMed1978

Unsustained multiplication of treponema pallidum (nichols virulent strain) in vitro in the presence of oxygen.

Treponema pallidum (Nichols virulent strain) was incubated with or without oxygen using a modified medium supplemented with reduced glutathione and a variety of nutrients (PRNF10-B). Two- to fourfold increases in treponemal numbers were observed in cultures without mammalian cells within 96 h of incubation under 5 to 6% oxygen. Treponemal motility and multiplication were maintained more satisfactorily in cultures that were diluted and transferred daily, using an equal volume of fresh medium. Treponemes incubated without oxygen did not significantly increase in number. Virulent microorganisms were detected for at least 96 h in the cell-free system. In the presence of 3 to 4% oxygen, two- to fivefold increases in treponemal numbers were observed in the supernatant fluids of cultures containing human prepuce cells after 48 to 120 h at 35 degrees C. Without oxygen, treponemal numbers rarely approached a threefold increase. Virulent treponemes were detected by the rabbit skin lesion test after at least 120 h in vitro. Regardless of the system of incubation, increases in treponemal numbers could not be sustained for longer than 120 h, and treponemal virulence decreased as a function of time in vitro.

Animals↗
PubMed1978

The annual reproductive cycle of captive Macaca sylvana.

The annual reproductive cycle of a captive colony of Barbary apes, Macaca sylvana, was examined for the 26-year period from 1950 to 1976 and then compared with the annual reproductive cycle of semifree ranging M.sylvania in Gibraltar. Mating and birthing seasons for the two populations were similar although birth synchrony was more pronounced in the Gibraltar colony. The environmental factors influencing the maintenance of the annual cycles in both localities are examined.

Animals↗