Following IV administration,
the plasma concentration vs time data of norfloxacin in goldfishes
were fitted to a two-compartment open model system according to
the following bi-exponential equation [9]: C
p
=Ae-αt+Be-βt
where C
p
is the concentration of drug in the plasma at time t,
A and B are the zero-time drug intercepts of the distribution and
elimination phase expressed as μg ml-1, α and β are the distribution
and elimination rate constants expressed in units of reciprocal time
(h-1), and e is the natural logarithm base.
For the IV data, the appropriate pharmacokinetic model was
determined by visual examination of individual concentration-time
curves and by application of Akaike’s Information Criterion (AIC)
[10]. The volume of distribution at steady state (Vdss), the total body
clearance (Cl) and mean residence time (MRT) were computed
according to standard equations [11]. Following PO administration,
plasma concentration data in fishes were analyzed by compartmental
and non compartmental methods based on the statistical moment
theory [11]. In compartmental analysis, best fitting of the data was
accomplished using the one compartment open model. The area
under the concentration time curve (AUC), and area under the first
moment curve (AUMC), was calculated by the method of trapezoids.
Mean residence time (MRT) was calculated as MRT=AUMC/
AUC and the systemic clearance as Cl=Dose/AUC. The absolute
bioavailability was calculated as F=AUCIM or PO/AUCIV×100. Mean
absorption time was calculated as MAT=MRT
poMRT
IV.
The data were analyzed using SPSS (16) software (SPSS Inc.,
Chicago, USA) and differences between the averages were examined
by Duncan’s multiple-range test. Mean values within a row with
different superscript letters are significantly different (P< 0.05).