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Table 3 Pharmacokinetic Parameters of Gentamicin Concentrations in Perilymph

From: Mannitol and the blood-labyrinth barrier

Parameter Gentamicin(ng/ml) given alone in Perilymph (95%CI) Gentamicin(ng/ml) with Mannitol in Perilymph (95%CI) p = 0.0044
Ymax 70 (55–84) 64 (55–72) n.s.
k1 0.50 (0.25–0.75) 1.0 (0.42–1.6) *
k2 0.11 (0.49–0.18) 0.31 (0.17–0.45) *
R 2 0.59 0.69  
  1. Data were fitted to the eq. 2 as in Fig. 2 but there were significant differences between the model with gentamicin (n = 43) and without gentamicin (n = 44) (p = 0.0044), indicating that mannitol changed the permeability of the blood-labyrinth barrier. Without mannitol and (+/− 95% confidence interval), the parameters were ymax = 70 (+/− 55–84) ng/ml; k1 = 0.50 (+/−0.25–0.75) hrs−1 with t1/2 = 12.6 h; k2 = 0.11(+/− 0.49–0.18) hrs−1 with (t1/2 = 6.3 h); R2 = 0.59. With mannitol and (+/− 95% confidence interval), the parameters were ymax = 64 (+/− 55–72) ng/ml; k1 = 1.0 (+/− 0.42–1.6) hrs−1 with t1/2 = 0.69 h; k2 = 0.31 (+/− 0.17–0.45) hrs−1 with t1/2 = 2.2 h; R2 = 0.69. Ymax is not statistically significantly different but k1 and k2 are (both p < 0.05), indicating that mannitol caused increased permeability of the blood-labyrinth barrier to gentamicin, allowing more rapid entry and egress and subsequently lower concentration. The parameterized equations for gentamicin concentration without mannitol, then was \( \Big[y(t)=70\left[{e}^{-0.5t}+\left(1-{e}^{-{0.11}_{\left(t-4\right)}}\right)\right] \), and the equation with mannitol was \( \Big[y(t)=64\left[{e}^{-t}+\left(1-{e}^{-{0.31}_{\left(t-4\right)}}\right)\right] \)