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Biomedical subjects

D F McCafferty

Publications and source records attributed to D F McCafferty.

18 recordsLinked to original sources
PubMed1991

The effects of three non-antibiotic, antimicrobial agents on the surface hydrophobicity of certain micro-organisms evaluated by different methods.

The effects of three non-antibiotic, antimicrobial agents (taurolidine, chlorhexidine acetate and providone-iodine) on the surface hydrophobicity of the clinical strains Escherichia coli, Staphylococcus saprophyticus, Staphylococcus epidermidis and Candida albicans were examined. Three recognized techniques for hydrophobicity measurements, Bacterial Adherence to Hydrocarbons (BATH), the Salt Aggregation Test (SAT) and Hydrophobic Interaction Chromatography (HIC) were compared. At concentrations reported to interfere with microbial-epithelial cell adherence, all three agents altered the cell surface hydrophobicity. However, these effects failed to exhibit a uniform relationship. Generally, taurolidine and povidone-iodine treatments decreased the hydrophobicity of the strains examined whereas chlorhexidine acetate effects depended upon the micro-organism treated. Subsequently, the exact contribution of altered cell surface hydrophobicity to the reported microbial anti-adherence effects is unclear. Comparison of the three techniques revealed a better correlation between the results obtained with the BATH test and HIC than the results obtained with the BATH and SAT or SAT and HIC. However, these differences may be due to the inaccuracy associated with the visual assessment of results employed by the SAT.

Anti-Bacterial Agents↗
PubMed1990

Clinical experiences with a novel percutaneous amethocaine preparation: prevention of pain due to venepuncture in children.

1. The efficacy and safety of a novel percutaneous anaesthetic preparation based on amethocaine has been investigated in the paediatric clinical environment. 2. There were 1241 recorded applications on a named patient basis made to patients from infant to age 16 years. Of these, 88.7% had satisfactory anaesthesia to venepuncture challenge, rising to approximately 90% when the infant group was excluded. 3. A 30 min application time was found to be adequate for reliable topical anaesthesia. 4. There were no serious adverse reactions to the preparation. Of the total 6.9% recorded reactions, 6.3% were of a mild, transient erythema later identified as due to the vasodilator action of the drug. 5. A total of 123 patients received more than one application of the preparation. There was no evidence of sensitisation on subsequent exposure to the preparation. 6. The short application time required was found to be advantageous to ward and clinic routines.

Adolescent↗
PubMed1989

In vivo assessment of percutaneous local anaesthetic preparations.

This study has demonstrated greater efficacy of a new percutaneous amethocaine preparation relative to Eutectic Mixture of Local Anaesthetics (EMLA). Initially, a double-blinded trial was undertaken on each preparation individually against placebo, as the recommended method of application was different for EMLA (2.5 g applied for 60 min under an occlusive dressing) and the amethocaine formulation (0.5 g applied for 30 min). Thereafter, the two preparations were compared directly, in a double-blinded study using a standardized application for both formulations. The results indicated that both preparations provided significant (chi-square; P less than 0.001) percutaneous local anaesthesia when compared with placebo. The amethocaine preparation produced significant anaesthesia (chi-square, P less than 0.001) after 30 min application. Furthermore, the amethocaine formulation demonstrated both increased rapidity of action and increased duration of effect, as determined by a two-tailed unpaired t test, in comparison with EMLA when application times of both 30 and 60 min were used for each preparation. The results of this study indicate that the amethocaine preparation provided more rapid and prolonged anaesthesia than EMLA.

Administration, Cutaneous↗
PubMed1989

Local anaesthesia of the skin.

Local anaesthesia of intact skin is of growing importance given the increased use of minor surgical procedures on an out-patient basis. Specific pain receptors (nociceptors) are responsible for sensing cutaneous pain. Mechanisms of pain perception and the role of local anaesthetics in reversibly blocking nociception are considered. Effective routes of administration are dermal infiltration or, more recently, anaesthesia by topical application of specifically formulated preparations which promote percutaneous absorption of the drug (percutaneous local anaesthesia). Although many other topical anaesthetic products are also available these do not permit the anaesthetic to reach the nociceptors underlying the stratum corneum and are therefore only suitable for mucosal anaesthesia or for application to damaged skin. The chemical characteristics of local anaesthesia drugs are identified. Those agents suitable for cutaneous anaesthesia are reviewed with respect to potency, onset and duration of anaesthesia and possible systemic or local adverse reactions.

Anesthesia, Local↗
PubMed1988

Pain-free cutting of split skin grafts by application of a percutaneous local anaesthetic cream.

The use of a novel percutaneous anaesthetic preparation for the pain-free cutting of split skin grafts has been assessed in a series of 80 patients, age range 12 to 96 years. The technique was completely successful in 80% of these cases, with complete analgesia established within one hour of initial application. Duration of anaesthesia was such that pain-free cutting of the skin was possible up to 5 hours after initial application of the preparation. Failures of the technique were largely attributed to a loss of anaesthetic potency in the preparation, application of an inadequate amount to the site or patient anxiety. The use of the percutaneous anaesthetic preparation was found to offer considerable advantages over conventional infiltration anaesthesia for this type of surgery. Several additional surgical applications of percutaneous anaesthesia are also considered.

Administration, Cutaneous↗
PubMed1988

Comparative in vivo and in vitro assessment of the percutaneous absorption of local anaesthetics.

The percutaneous absorption of local anaesthetics in a standard formulation has been compared in vitro and in vivo. In vitro data were obtained with a modified Sartorius absorption system and silastic as a lipophilic barrier membrane. With this system the greatest steady-state flux values and permeability coefficients were obtained with amethocaine and lignocaine. These drugs also performed best in an in vivo volunteer trial. However, statistical analysis revealed that amethocaine was significantly better at producing full-depth anaesthesia to the challenge of insertion of a sterile needle. An optimized amethocaine formulation may therefore be expected to meet most closely the ideal profile for a percutaneous local anaesthetic preparation.

Anesthesia, Local↗
PubMed1988

Concentration-response analysis of percutaneous local anaesthetic formulations.

The percutaneous absorption of amethocaine has been measured for different concentrations of the drug in three different formulations, A, B and C. Statistical analysis indicated that a concentration of 4% produced effective percutaneous local anaesthesia to pin-prick, together with an acceptable onset time of approximately 40 min. Increasing the concentration did not reduce the onset time further, although there was some increase in the duration of anaesthesia. Formulations A and B were hydrophilic, whereas C was an oil-in-water cream. Effective anaesthesia with formulation C required a higher drug concentration (12%), perhaps because of partitioning of the lipophilic anaesthetic into the lipid phase of the vehicle. The rate-limiting step was considered to be diffusion by the lipophilic anaesthetic through the stratum corneum, shown by onset of anaesthesia after removal of the formulation from the test site.

Administration, Cutaneous↗
PubMed1987

On the statistical evaluation of adherence assays.

Parametric (unpaired t-test) and non-parametric (Mann-Whitney U-test) methods have been used in the evaluation of adherence assays on the non-antibiotic antimicrobial agent, Taurolin. In all but one case, where the anti-adherence effect was known to be marginal, both statistical methods gave similar results although there were some minor differences in the levels of significance achieved. The effect of the agent on the deviation of adherence data from normality was quantified by calculation of the skewness coefficient for each data set. A significant anti-adherence effect appears to result in a decrease in the skewness of the adherence assay data. It was concluded that either parametric or non-parametric statistical evaluation of adherence assay data is valid for large numbers of observations. In future studies of this type it is suggested that attention should also be given to the effect of the anti-adherence agent on the deviation of adherence data from normality as denoted by the skewness coefficient.

Adhesiveness↗
PubMed1987

Reduced adherence of micro-organisms to human mucosal epithelial cells following treatment with Taurolin, a novel antimicrobial agent.

Taurolin, a non-antibiotic antimicrobial agent, significantly reduced the adherence of buccal and vaginal strains of Candida albicans blastospores and urine isolates of Escherichia coli and Staphylococcus saprophyticus to epithelial cells. Light microscopy and radio-isotopic counting methods were used to quantify the adherence of the micro-organisms to either uroepithelial or buccal epithelial cells. A maximum reduction in adherence of approximately 65% was obtained. The anti-adherence capacity was time-dependent, requiring a contact time of 30 min to achieve maximum effect. Taurolin at sub-minimum inhibitory concentrations (MIC) significantly reduced the adherence of Candida and E. coli. A concentration slightly higher than the MIC was required for Staph. saprophyticus. Treatment of either epithelial cells or micro-organisms with Taurolin resulted in reduced adherence of microorganisms.

Anti-Bacterial Agents↗
PubMed1987

A comparative study of the microbial antiadherence capacities of three antimicrobial agents.

The antimicrobioal agents, taurolidine, chlorhexidine and povidone-iodine were examined for microbial anti-adherence activity. Two adherence systems were investigated using light microscopic and radio-isotopic assay methods: that of an oral isolate of Candida albicans to human buccal epithelial cells and of a urine isolate of Escherichia coli to human uroepithelial cells. Each of the three agents exhibited significant anti-adherence activity which was concentration dependent. The activity was expressed at subminimum inhibitory concentrations of the agents. Treatment of either the microbial or epithelial cells resulted in significant reductions in adhering micro-organisms. Consideration of the data in respect of the skewness coefficient and percentage clear epithelial cells indicated that the agents exhibited a broadly based anti-adherence capacity.

Anti-Bacterial Agents↗
PubMed1986

Decrease in adherence of bacteria and yeasts to human mucosal epithelial cells by noxythiolin in vitro.

Adherence of buccal and vaginal isolates of Candida albicans to buccal epithelial cells and the adherence of urine isolates of Escherichia coli and Staphylococcus saprophyticus to uroepithelial cells was quantified by light microscopy. The antimicrobial agent noxythiolin reduced the adherence of these micro-organisms in both exponential and stationary growth phases. Adherence of both the blastospore and pseudohyphal forms of C. albicans was reduced. Treatment of epithelial cells and/or micro-organisms with noxythiolin resulted in decreased adherence. No anti-adherence effect was observed with formaldehyde and N-methylthiourea, the degradative products of noxythiolin.

Adhesiveness↗
PubMed1986

Inhibition of hyphal development and kill of Candida albicans blastospores by noxythiolin in vitro.

The cidal activity of the antimicrobial agent, noxythiolin, was investigated against a laboratory strain and a fresh isolate of Candida albicans. The order of resistance to noxythiolin was hyphal form (isolate) greater than or equal to 25 degrees C-grown blastospores (isolate) greater than 37 degrees C-grown blastospores (isolate) greater than laboratory strain blastospores. Noxythiolin activity was superior to that of 'equivalent' formaldehyde concentrations. Mycelial transformation in C. albicans was examined by light and scanning electron microscopy and measured in terms of percentage germination and hyphal extension. Noxythiolin, 2.5%, in contact for 30 min prevented germination of the blastospore population whereas the decomposition products, formaldehyde and N-methylthiourea, showed no appreciable effect in the expected concentrations. The implications of these results are discussed in relation to the observed clinical efficacy of noxythiolin.

Candida albicans↗
PubMed1985

The effect of ultrasound on the percutaneous absorption of lignocaine.

The influence of ultrasound on the percutaneous absorption of lignocaine from a cream base was investigated in a double-blind cross-over trial in healthy volunteers. Mean data indicated that there was a slightly faster onset time for local anaesthesia when ultrasound was administered when compared with control values (no ultrasound). However, the differences were not statistically significant. Further controlled clinical studies are required into the effect of ultrasound on percutaneous absorption since the technique (phonophoresis) has been alleged to enhance percutaneous penetration of a number of drugs.

Double-Blind Method↗
PubMed1985

Differential pulse polarographic determination of formaldehyde in stored noxythiolin solutions.

A differential pulse polarographic method has been developed for the determination of formaldehyde, by means of its kinetic current, in noxythiolin solutions. The assay conditions have been optimized so that the noxythiolin decomposition reaction was not affected. The method had the advantage of rapidity with an analysis time of about 10 min per sample. Thus formaldehyde was determined in noxythiolin solutions prepared and stored under typical clinical conditions. The low concentrations of formaldehyde present in all solutions were insufficient to account for the known cidal action of noxythiolin. There must therefore be some doubt that the mode of action of noxythiolin is simply due to formaldehyde produced as a result of the decomposition of noxythiolin in aqueous solution.

Drug Stability↗
PubMed1985

A comparison of the antimicrobial activities of noxythiolin and formaldehyde solutions.

The availability of a rapid and highly specific polarographic method of analysis for formaldehyde enabled investigation of the rate of formaldehyde release from noxythiolin solutions and actual concentrations of formaldehyde in solutions during clinical use and storage. The antimicrobial activity of noxythiolin solutions, equivalent pure formaldehyde solutions and N-methylthiourea individually or in combination was examined against standard bacteriological strains and clinical isolates. Several interesting observations were made. Clinical isolates were found to be relatively susceptible to noxythiolin in contrast to laboratory strains. The growth phase of the organism radically affects activity, early exponential phase cells being susceptible to 1.0% noxythiolin. Levels of formaldehyde detected in fresh noxythiolin solutions are extremely low and would not appear to be solely responsible for the antimicrobial activity observed.

Bacteroides fragilis↗
PubMed1982

Effect on particle size on the compaction mechanism and tensile strength of tablets.

The effect of particle size variation on tablet tensile strength for spray-dried lactose, Sta-Rx 1500 and Avicel PH-101 was investigated. Decreasing the particle size of spray-dried lactose and Sta-Rx 1500 resulted in stronger compacts whereas the tablet tensile strength of Avicel PH-101 was unaffected by particle size variation. The Heckel relationship, at two different contact times, was used to examine the predominant compaction mechanism. This was independent of the size fractions studied for all three materials. Angle of repose and Hausner ratio measurements indicated a correlation between the internal forces of friction and cohesion of the sized powders and the tensile strength of compacts formed from them.

Hardness↗