This webinar was presented on June 30, 2021 by David R. Taft, Ph.D. Professor, Pharmaceutics, Long Island University, NY, USA.
Here is a summary of his presentation:
• Tizanidine is an alpha2-adrenergic agonist, used to treat spasticity associated with multiple sclerosis and spinal injury. Tizanidine is primarily metabolized by CYP1A2 and is considered a sensitive index substrate for this enzyme.
• The physiologically based pharmacokinetic (PBPK) modeling platform Simcyp® was used to evaluate the impact of CYP1A2 modulation on tizanidine exposure through drug-drug interactions (DDIs) and host-dependent habits (cigarette smoking).
• A PBPK model was developed to predict tizanidine disposition in healthy volunteers following oral administration. The model was verified based on agreement between model-simulated and clinically observed systemic exposure metrics (Cmax, AUC).
• The model was then used to carry-out DDI simulations to predict alterations in tizanidine systemic exposure when co-administered with various CYP1A2 perpetrators including competitive inhibitor (fluvoxamine), a mechanism-based inhibitor (rofecoxib), and an inducer (rifampin). Additional simulations were performed to evaluate the impact of cigarette smoking on systemic exposure.
• Under each scenario, the PBPK model was able to capture the observed fold changes in tizanidine Cmax and AUC when coadministered with CYP1A2 inhibitors or inducers.
• These results supplement the available research findings in the literature on PBPK predictions of drug-drug interactions and illustrate its potential application in drug development, specifically to support product labeling.