A population pharmacokinetic model is beneficial in quantifying hair concentrations of ritonavir-boosted atazanavir: a study of HIV-infected Zimbabwean adolescents

Table 5 Final model parameters describing joint fixed plasma and hair pharmacokinetics of ritonavir

Parameter	Population mean (SE as %)	1000 samples bootstrap medians (90% CI)	Variability (SE as %)	1000 samples bootstrap medians (90% CI)
k₁₂ (litres hour⁻¹)	2.31 fixed	2.31 fixed	0.45 fixed	0.45 fixed
CL/F (litres hour⁻¹)	12.8 fixed	12.8 fixed	0.28 (31)	0.28 (0.01 to 0.68)
V_c (litres)	105 fixed	105 fixed	0.50 fixed	0.50 fixed
F_rac	0.18 (16)	0.18 (0.14 to 0.21)
V_h (litres)	1 fixed	1 fixed
Occasion (Follow-up)_ F_rac	*	*
Occasion (Enrolment)_ F_rac	−0.42 (22)	−0.39 (−0.56 to −0.21)
Adherence score_ F_rac	0.02 (47)	0.014 (0.008 to 0.017)
ɛADD	0.34 (95)	0.36 (0.04 to 0.63)
ɛPROP	0.26 (26)	0.24 (0.13 to 0.31)
σ	1	1

k₁₂: Absorption rate constant; CL/F: apparent drug clearance; V_c and V_h: apparent volume of distribution in the central and hair compartments, respectively; F_rac: amount of drug cleared into the hair as a proportion of the amount of drug in plasma; FACTOR_ F_rac: effect of covariate on F_rac; ɛ_ADD and ɛ_PROP: additive and proportional error terms, respectively; σ: residual error; SE: standard error. *: reference category

ISSN: 2050-6511