TABLE 4

Parameter estimates for pyrazinamide and ethambutol in TB-HIV-coinfected patients

ParameterPyrazinamideEthambutol
Estimated valueRelative SE (%)Estimated valueRelative SE (%)
CL (liters/h)a2.97335.620
V (liters)a33.0380.517
Ka (h)3.0490.45411
Vp (liters)a,b649110
Qa,b43.732
Tlag (l/h)0.419120.816
F1 (fixed)1 (fixed)
Proportional error (%)0.051831.74
Additive error (mg/liter)2.49120.25 (fixed)d
Between-subject variability of CLc (%CV)30.1733.917
Between-subject variability of Vc (%CV)15.11177.212
Between-occasion variability of Kac (%CV)64.2736.726
Between-occasion variability of Tlagc (%CV)66.71222.832
Between-occasion variability of Fc (%CV)16.7430.69
  • a Allometric scaling was used for CL, Vc, Q, and Vp, and values are reported for the median weight of the cohort (52 kg).

  • b Q and Vp were estimated using Bayesian priors, with typical values of 64.4 liters/h and 420.7 liters, respectively, from a previous study (7), with 50% uncertainty.

  • c The between-subject and between-occasion variability values were assumed to be log-normally distributed and are reported as approximate coefficients of variation (%CV).

  • d The estimate of the additive error was approximating zero and was therefore fixed to half the value of the lowest limit of quantification (0.5 mg/liter).