Using In Vitro Data to Estimate In Vivo Starting Doses for Acute Toxicity 3.0 PROCEDURE FOR QUALIFYING A CYTOTOXICITY TEST FOR USE WITH THE REGISTRY OF CYTOTOXICITY (RC) PREDICTION MODEL

Workshop participants agreed that tests of basal cytotoxicity were sufficiently predictive for the rodent LD50 such that cytotoxicity tests could be used to predict a starting dose for an in vivo lethality assay (NIEHS, 2001). This section discusses how to proceed. Theoretically, any in vitro test capable of determining basal cytotoxicity could be used to determine the best estimate of a starting dose for acute testing in the UDP (OECD, 1998b), the ATC method (OECD, 1996), or the Fixed Dose Procedure (FDP; TG 420, OECD, 1992). In addition, if the LD50 predicted from cytotoxicity is high (i.e., ≥ 2,000 mg/kg b.w.), a range-finding study for the ATC or FDP may not be necessary, as testing could be initiated using the limit test of 2,000 or 5,000 mg/kg.