Table 2. Tenofovir concentrations and infant exposure.
| Variable | All infants | Infant age ≤12 wk | Infant age 13–24 wk | p-value |
|---|---|---|---|---|
| Peak * | n = 98 | n = 49 | n = 49 | |
| Maternal plasma concentration in ng/mL | 152.0 (56.9–321.0) | 140.5 (53.3–327.5) | 165.5 (58.4–309.0) | |
| Breast milk concentration in ng/mL | 3.2 (2.3–4.7) | 3.8 (2.7–6.9) | 2.9 (2.1–3.8) | |
| M/P concentration ratio | 0.03 (0.01–0.05) | 0.03 (0.02–0.07) | 0.02 (0.01–0.04) | |
| Proportion of infant plasma samples with concentration below the lower limit of quantification† | 94% (46/49) | 96% (23/24) | 92% (24/25) | |
| Infant daily dose from breast milk in μg/kg | 0.47 (0.35–0.71) | 0.57 (0.41–1.04) | 0.44 (0.32–0.56) | 0.06 |
| Infant dose fractionⱡ | <0.01% (<0.01–0.01) | <0.01% (0–0.02) | <0.01% (<0.01–0.01) | 0.06 |
| Trough * | n = 97 | n = 48 | n = 49 | |
| Maternal plasma concentration in ng/mL | 51.9 (40.7–59.6) | 54.1 (45.7–62.3) | 46.0 (39.4–57.2) | |
| Breast milk concentration in ng/mL | 3.3 (2.3–4.4) | 3.5 (2.3–6.8) | 3.2 (2.3–3.8) | |
| M/P concentration ratio | 0.07 (0.05–0.08) | 0.07 (<0.01–0.31) | 0.07 (<0.01–0.11) | |
| Infant daily dose from breast milk in μg/kg | 0.49 (0.34–0.66) | 0.52 (0.05–0.08) | 0.49 (0.05–0.08) | 0.11 |
| Infant dose fractionⱡ | <0.01% (<0.01–0.01) | <0.01% (<0.01–0.01) | <0.01% (<0.01–0.01) | 0.11 |
Unless stated, statistics are median (interquartile range). n are for samples tested, with each woman providing a maximum of two of respective records (i.e, one on day 7 and another on day 10), while each infant provided one record.
*Peak maternal blood, breast milk, and infant blood samples were obtained after a median (IQR) of 63 (60 to 68), 70 (65 to 77), and 80 (45 to 90) min after maternal DOT PrEP dose, respectively, while maternal trough samples were obtained a median of 23 h (IQR 23 to 24) from the previous maternal DOT PrEP dose.
† n = 49, a single infant plasma sample was obtained: 24 samples for ≤12 wk age group and 25 samples for 13–24 wk age group. Only 3 of 49 infant plasma samples had detectable tenofovir concentration in plasma (Infants aged 11 and 13 wk [both had 0.9 ng/mL] and 17 wk [17.4 ng/mL]).
ⱡ Infant dose fraction, represents the daily amount of tenofovir dose an infant would be expected to ingest from breast milk as a percentage of the proposed therapeutic daily dose (6 mg/kg).
p-Values are from Mann–Whitney U test testing the null hypothesis that the two infant age groups are drawn from the same distribution.
M/P, milk to maternal plasma ratio; Lower limit of quantification was <0.31 ng/mL in plasma and <1 ng/mL in whole breast milk.