Table 3

Parameter estimates based on the final rifampin pharmacokinetic-enzyme turnover modela

ParameterEstimated value% RSE
TV(CL/F)STD (liters · h−1)10.03.7
TV(V/F)STD (liters)86.72.3
MTT (h)0.7131.6
No. of transit compartments1 FIX1 FIX
Emax1.042.6
EC50 (mg · liter−1)0.07056.3
kENZ (h−1)0.003695.6
CL-V correlation (%)91.120.7
(Ffat)CL/F0.31140.2
(Ffat)V/F0.18849.1
IIVCL/F (%)30.012.3
IIVV/F (%)19.214.8
IIVEC50 (%)493.019
IOVMTT (%)68.07
IOVF (%)16.211.2
V/F-HIV (%)29.617.2
Additive error (mg · liter−1)0.9652.8
Proportional error (%)9.94.7
  • a IIV, interindividual variability expressed as a coefficient of variation; IOV, interoccasion variability expressed as a coefficient of variation; RSE, relative standard error reported on the approximate standard deviation scale; TV(CL/F)STD, the typical oral clearance at the preinduced state in a patient weighing 70 kg; TV(V/F)STD, the typical apparent volume of distribution in a patient weighing 70 kg; MTT, mean transit time; Emax, maximal increase in the enzyme production rate; EC50, rifampin concentration at which half the Emax is reached; kENZ, rate constant for first-order degradation of the enzyme pool; CL-V correlation, correlation between CL/F and V/F; (Ffat)CL/F, estimated contribution of fat-free mass and body weight to CL/F; (Ffat)V/F, estimated contribution of fat-free mass and body weight to V/F; V/F-HIV, increase in apparent volume of distribution in HIV-infected patients; 1 FIX, number of transit compartments fixed to 1.