Table 2.
Genital and Plasma Antiretroviral Drug Concentrations (C24h)a and Within- and Between-person Variabilityb
| Antiretroviral drug |
|||
|---|---|---|---|
| FTC | TFV | ATV | |
| Geometric mean genital C24h, ng/mL (95% CI) | 903 (628–1299) | 244 (159–374) | 1440 (1020–2032) |
| Within-person CV, % | 66.1 | 81.9 | 82.4 |
| Between-person CV, % | 74.8 | 93.0 | 64.0 |
| Geometric mean plasma C24h, ng/mL (95% CI) | 76 (58–99) | 69 (54–88) | 601 (477–757) |
| Within-person CV, % | 47.4 | 41.2 | 70.7 |
| Between-person CV, % | 54.0 | 50.4 | 38.4 |
| Genital: plasma C24h geometric mean ratio (95% CI) | 11.9 (8.66–16.3) | 3.53 (2.27–5.48) | 2.39 (1.69–3.38) |
Abbeviations: ATV, atazanavir; C24h, concentration 24 hours after last dose; CI, confidence interval; CV, coefficient of variation; FTC, emtricitabine; TFV, tenofovir.
a 96 study visits from 19 subjects occurred within 2 hours of the next scheduled antiretroviral dose and were included in analysis.
b For natural log drug concentration data, the standard deviation is approximately equal to the CV in the original scale. Therefore, the within- and between-person CVs can be used as estimates of the within- and between-person standard deviations.