Physiological modeling of formulated and crystalline 3,3′-diindolylmethane pharmacokinetics following oral administration in mice

3,3'-Diindolylmethane (DIM) is a naturally occurring indole, which is currently under investigation as a potential chemopreventive agent. The concentrations of DIM in plasma, liver, kidney, lung, heart, and brain tissues were determined following oral administration of two different formulations to mice (250 mg/kg). Mice were sacrificed periodically from 0 to 24 h after administration of either a crystalline or an absorption-enhanced formulation (BioResponse-DIM; Indolplex) of DIM, and plasma and tissue concentrations were determined by high-performance liquid chromatography (UV detection, 280 nm). A physiologically based pharmacokinetic (PBPK) model was developed to characterize the pharmacokinetic properties of the two different formulations. The final model included parameters reflecting linear first-order absorption, systemic clearance, and distributional clearance in the remainder compartment, which were considered independent of formulation. All pharmacokinetic profiles from the two formulations were fitted simultaneously to estimate unknown model parameters. Plasma and tissue concentration-time profiles exhibited a rapid rise to peak values at 0.5 to 1 h, followed by a polyexponential decline with an extended terminal phase. These profiles were well described by the final model and unknown parameters were estimated with relatively low coefficients of variation. Relative drug exposure and absorption parameters suggest that BioResponse-DIM exhibited approximately 50% higher bioavailability than the crystalline formulation. Clearance of DIM was estimated as 7.18 ml/h. This is the first study to characterize the pharmacokinetics of DIM in mice, and the established PBPK model should prove useful in the design and analysis of future preclinical studies aimed at evaluating the in vivo pharmacological effects of DIM.