Results and discussion
Drug content and viscosity.
All prepared cream formulations of BRB contained 99.2–100.1% of the indicated amount of BRB. As the concentration of menthol
increased in the formulations, the viscosity decreased in both gel formulations (see Table III).
The results of the experiments on the antimicrobial effectiveness of the various cream formulations of BRB, as measured by
the diameter of zone of inhibition (mm), are presented in Figure 1. The combination of variables significantly influenced
the effectiveness of the cream formulations. All the creams generally showed considerable effectiveness against S. aureus. In the case of C. albicans, creams with a BRB concentration of 0.5% and 1.0% w/w had little effectiveness. The effectiveness of the creams, however,
increased considerably with an increase in BRB concentration.
The relevant values of the zones of inhibition were used to calculate the independent and interaction coefficients of the
variables' influence on the creams' effectiveness. The values of the coefficients are presented in Table II. The variables
had positive and negative influences on the cream formulations' effectiveness. A positive influence was increased inhibition
of bacterial growth, and a negative influence was a decreased inhibitory effect on bacterial growth.
The independent coefficient values show the influence of individual variables on the effectiveness of the cream formulations
(see Table II). The effects of the variables were highly dependent on the concentration of BRB in the formulation.
Table II: Quantitative effects of type of emulsifier (T), concentration of emulsifier (C), and time of storage (S) on the
diameter of zone of inhibition (mm) for BRB creams against Staphylococcus aureus and Candida albicans.
The type of emulsifier had by far the greatest effects on the inhibitory value of the creams, especially at higher concentrations
of BRB. The effects of T were generally positive, indicating that a change in emulsifier from Plurol, the low level of T, to Apifil, the high level of T, increased the creams' antimicrobial effectiveness. T had a much greater effect on the creams' effectiveness against C. albicans than did C and S at all concentrations of BRB.
C generally had moderate effects on the inhibitory value of the creams, especially at higher concentrations of BRB, where these
effects were generally positive. This result indicates that changing the concentration of emulsifier from 5 to 10% would increase
the effectiveness of the creams that contained higher concentrations of BRB.
S generally had the least effects on the inhibitory value of the creams, and thus the time of storage should be the least influential
variable. The effects were all negative, thereby showing that the creams' effectiveness decreases with time. This reduction
in effectiveness is negligible, however, because the creams stored for 12 months showed a similar zone of inhibition to that
of creams stored for no time.