Lakhasly

The antimicrobial preservative efficacy of the
eye-drops challenged with E. coli, S. aureus and
P. aeruginosa is shown in Table 1.Viable
microbial count, as recommended in both
Pharmacopeia, was determined by plate count
method using 1 ml of 1:10 dilution of product in
neutralizer and no bacterial growth means that the
number of challenging bacteria was reduced to
lower than 10 CFU per ml of the product instead
of NR. Therefore, it seems that the term of NR
should define an acceptable range.The
preservative employed in phenylephrine zinc eyedrop did not possess adequate antimicrobial
activity against P. aeruginosa to be able to bring
about acceptable low levels of microbial
contamination as demanded by regulatory bodies.Other eye-drops showed appropriate reductions in
bacterial viability after 6 hrs, 24 hrs and 7 days,
except a very low bacterial recovery after 28 days
(10-50 CFU ml-1
) which didn't comply with the
no recovery (NR) term of BP 'A' criteria.After a contact
time of 6 hrs all the eye-drops except
phenylephrine zinc which showed only 1.7 logs
reduction in P. aeruginosa initial count, reduced
at least 2 logs of all bacterial counts.The
number of P. aeruginosa in phenylephrine zinc
was reduced 2 logs after 24 hrs of inoculation and
was increased to about the initial count after 7
days.After 14 days, all the eye-drops except
phenylephrine zinc which showed 1 log reduction
in P. aeruginosa count appeared well preserved
against all the challenging organisms (?3 logs
reduction).As shown in Table 3, more than 2 logs reduction
in bacterial counts (after 30 min) and more than 3
logs reduction in fungal counts (after 24 hrs) were
observed for all eye-drops except phenylephrin
zinc.Most of the eye-drops eradicated the inoculated
microorganisms more than 3 logs in 24 hrs and
also 7 days, except phenylephrine zinc.After 28 days, there was no bacterial recovery
from betamethasone eye-drop, while the number
of P. aeruginosa in phenylephrine zinc increased.The results of this study showed that eight out of
the nine products met the BP 'B' criteria and USP
while all of them except artificial tear were highly
contaminated during hospital uses (Table 4).Other eye-drops showed no increase in bacterial
counts after 28 days which were about 10-50 CFU
ml-1
of the products. In all cases the number of fungi after 7 and 14
days were acceptable and those after 28 days were
at least 2 logs lower than the initial counts (Table
2).Therefore another effective antimicrobial
preservative system for this formulation should be
employed.