FIG 4.
Probability of ototoxicity as a function of three different parameters. The probability of ototoxicity as a function of cumulative AUC is sigmoidal, with the TC50 of 87,232 days · mg · h/liter shown in the equation. This value is very close to the 91,914 days · mg · h/liter identified by CART. The more continuous relationship between concentration and toxicity can be used to calculate the cumulative AUC versus the probability and risk of toxicity that can be tolerated by clinicians and patients. (B) Probability of ototoxicity as a function of patient weight. Since this is a nonmodifiable patient factor at the time when a patient presents with MDR-TB, it would not factor much in the decision making. (C) Probability of ototoxicity as a function of duration of therapy. The risk increases at the inflection point of 6 months and is a near certainty at 9 months.