Search PubMed⌕ Search

Biomedical subjects

D A Norton

Publications and source records attributed to D A Norton.

9 recordsLinked to original sources
PubMed1979

Control of glaucoma by reduced dosage guanethidine-adrenaline formulation.

The effect of formulations of guanethidine and adrenaline of different composition has been tested in rabbits and in patients with glaucoma. The concentrations of guanethidine and adrenaline used for the rabbits were 5.0% and 1.0%; 2.5% and 0.5%; 1.0% and 0.2%; 0.5% and 0.1%. All except the lowest combination were equally effective in the magnitude of the decrease in intraocular pressure brought about and in their duration of activity. Two formulations containing guanethidine and adrenaline at concentrations of 3.0% and 0.5% and 1.0% and 0.2% respectively (formulated as Ganda drops by Smith and Nephew Pharmaceuticals Ltd) were tested in a blind, cross-over, short-term clinical trial on 20 patients. The drops containing the lower concentration of drugs were as effective as those of higher concentration. These results lead us to believe that most patients who respond to this treatment could be put on a reduced dosage regimen, which should result in a decreased incidence and severity of side effects.

Aged↗
PubMed1978

The interaction of preservatives with polyhydroxyethylmethacrylate (polyHEMA).

The interaction of the four most commonly used preservatives in contact lens solutions (chlorbutol, thiomersal, chlorhexidine gluconate and benzalkonium chloride) with polyhydroxyethylmethacrylate (polyHEMA), has been examined. Benzalkonium chloride and chlorhexidine gluconate show typical high affinity type isotherms. The interaction of benzalkonium chloride with polyHEMA from aqueous solution was reversible whereas that of chlorhexidine was only reversible in the presence of electrolyte or surfactant. Chlorbutol showed a typical reversible linear isotherm. Thiomersal does not interact with polyHEMA above pH 5.0. The extent of chlorhexidine--polyHEMA interactions in increased by the presence of formulatory adjuvants such as electrolyte and hydrophilic polymers. PolyHEMA lenses that apparently have been equilibrated with chlorhexidine gluconate will, on the addition of fresh preservative solution, bind further quantities of chlorhexidine above that which would be predicted from the sorption isotherm.

Acrylic Resins↗
PubMed1977

Loss of antibacterial preservatives from contact lens solutions during storage.

The preservative content of 34 commercially available contact lens solutions has been determined. Over half of the solutions contained less than 90% of the stated preservative content. Storage tests conducted at 40 degrees, using both simulated and commercially available contact lens solutions in plastics containers of the type used to present these products showed that thiomersal and chlorbutol appeared to be sorbed by these containers in contrast to benzalkonium chloride and chlorhexidine gluconate which interacted mainly by a surface adsorption process. The extent of any interactions was dependent upon the type of plastics material used to fabricate the container.

Anti-Infective Agents, Local↗
PubMed1975

Effect of adrenaline and guanethidine in reducing intraocular pressure in rabbits' eyes.

The effect of Adrenaline 0.5 per cent and Guanethidine 2.5 per cent alone and in combination in reducing intraocular pressure in rabbits has been studied. Six rabbits were used and the efficiencies of 5 different dosage protocols was estimated both as intensity and duration of activity. The 5 dosage protocols were Adrenaline alone; Guanethidine alone; Adrenaline and Guanethidine together; Adrenaline followed in 30 min by ?Guanethidine; and Guanethidine followed in 30 min by Adrenaline. The single formulation containing both drugs appeared to be at least as efficient as the others. Eye drops containing 1 per cent Adrenaline and 5 per cent Guanethidine having sufficient stability for normal use have therefore been formulated.

Animals↗