Pharmacokinetic calculations
Specific pharmacokinetic parameters
were used to evaluate the effect of TPE on CFP/SUL including the amount
of drug eliminated during TPE (QPE);
the fraction eliminated by TPE
(fe %); Apparent volume of distribution (Vd); Area under the
plasma level versus time curve (AUC); Elimination rate constant (Kel);
Half-life (T1/2) and Drug clearance
(CL).
QPE was calculated as total volume of efluent port
(Vep)×concentration of CFP or SUL concentration from
effluent port (Cep); In the equation:
QPE=
Vep×Cep[12].
fe % can be calculated as
QPE/TBS × 100%.
Total Body Stores (TBS)=Vd×concentration before plasma exchange
[13].
Kel=(ln Ca-ln
Cb)/(Tb-Ta).
Tb-Ta, duration of two blood collection
time points, ln Ca and ln Cb, natural
log of plasma drug concentrations at the corresponding time points
Ta and Tb. KelTotal=(ln
C1-ln
C3)/(T3-T1). ln
C1, natural log of plasma concentration at start of TPE.
ln C3, natural log of plasma concentration at the end of
TPE; KelPatient=(ln C1-ln
C3)/(T3-T1) on session
II [4]; Definitions, the Elimination rate constant during TPE
(KelTotal) represents the contribution of durg removed
due to TPE and patient; The contribution of durg eliminated due to
patient is Kelpatient. T1/2 can be
calculated as 0.693/Kel [4].
Drug clearance while off TPE (CLpatient) was calculated
for the values of KelPatient×Vd [13, 14]. The Drug
clearance due to TPE (CLPE) was calculated using the
equation:
CLPE=QPE/AUCPE.
AUCPE, the AUC during TPE [12, 13]. Total drug
clearance (CLTotal) =
CLPE+CLpatient; The proportion of
%CLPE was determined by
CLPE/CLTotal×100%. Creatinine clearance
(Ccr) was calculated using the Cockroft-Gault equation [15].
Data were analyzed using the SPSS statistic version 22 (IBM; New York,
NY, United). The Paired-samples t-test was used to compare the
pharmacokinetics of the day with and
without TPE. Calculated values of <0.05 were considered to be
statistically significant. The correlation between plasma drug
concentration before TPE and QPE were analyzed by
Pearson’s correlation coefficient.