OpenAIR @ RGU >
Health and Social Care >
Pharmacy & Life Sciences >
Theses (Pharmacy & Life Sciences) >
Please use this identifier to cite or link to this item:
|Title: ||Studies on the stability and activity of polymyxin B solutions.|
|Authors: ||Saohin, Wipawee|
|Supervisors: ||Richards, R. M. E.|
Taylor, R. B.
|Issue Date: ||Sep-1997|
|Publisher: ||Robert Gordon University|
|Abstract: ||The correlation between the chemical stability and the microbiological activity of
polymyxin B in phosphate buffer pH 6.0 and in proprietary eye drops was evaluated.
High Performance Liquid Chromatography (HPLC) was used to quantify the amount
of the main components in samples stored at 43,50,55 and 60°C for a period of 500
h. The data indicated that there are significant differences in chemical stability
among the different proprietary eye drops. The accurate decomposition rate
constants and shelf-lives (~o) at 4°C of two of the six formulated eye drops and the
standard polymyxin B solution stored in glass containers at pH 6.0 were established.
It was concluded that microbiological assay by agar diffusion was unsuitable for
determining the activity of control polymyxin B in phosphate buffer and polymyxin
B in eye drops. Killing time determinations for polymyxin B against cell
suspensions of P. aeruginosa NCTC 6750 were consequently used. Thioglycollate
broth containingp- aminobenzoic acid (PABA) 0.16 %w/v and magnesium sulphate
1 %w/v was used as an inactivating recovery medium. The effect of preservatives
and of second antibacterials contained in the eye drops were tested individually and
combined with polymyxin B. Thiomersal 0.001 %w/v, trimethoprim 0.02 %w/v
and thiomersal 0.001 %w/v plus trimethoprim 0.02 %w/v did not have an effect on
the activity of polymyxin B 2000 U/ml. Neomycin was an exception and at the
concentrations in the range 0.0192 to 0.16 %w/v exhibited an antagonistic effect.
Chemical interaction between polymyxin B and neomycin could not be detected and it was considered that the inhibitory effect of neomycin may be the result of
competition between polymyxin B and neomycin for the same binding sites on the
Gentamicin is active against P. aeruginosa NCTC 6750 and at concentrations of
0.075 and 0.036 %w/v it exhibited an additive effect with polymyxin B 2000 U/ml
against the test organism.
The results obtained with the samples stored at 55°C for a period of 500 h
demonstrated the critical effect of pH. At a pH of 6.0 microbiological activity and
chemical stability appeared optimal. The chemical stability data of five eye drop
samples correlated with microbiological activity data. Exceptions were polymyxin
B in one eye drop sample and control polymyxin B. These extensively decomposed
samples showed good antibacterial activity which appeared to result from the
activity of decomposition products. Chemical stability data for standard polymyxin
B solution at pH 6.0 also correlated to microbiological activity data over the
temperature range of 92 - 115°C. The polymyxin B retained detectable
microbiological activity when the amount of PB1 was greater than 20%. It is
suggested that the decomposition products which occurred at these higher
temperatures did not possess antibacterial activity.|
|Appears in Collections:||Theses (Pharmacy & Life Sciences)|
All items in OpenAIR are protected by copyright, with all rights reserved.