Section 5.3 Preclinical Safety Data
In in vitroexperiments on isolated cells transfected with HERG and on isolated guinea
pig myocytes, exposure ratios were about 10 ranged between 5 and 30-fold,
based on IC50 values inhibiting currents through IKr ion channels in
comparison to the free plasma concentrations in humans after administration
of the maximum daily dose of 20mg (q.i.d.). Exposure margins for
prolongation of action potential duration in in vitro experiments on isolated
cardiac tissues exceeded the free plasma concentrations in humans at
maximum daily dose (20mg q.i.d) by 17-fold. However, safety margins in in
vitro experiments on isolated cardiac tissues pro-arrhythmic models (isolated
Langendorff perfused heart) and in in vivo models (dog, guinea pig, rabbits
sensitised for torsades de pointes) exceeded the free plasma concentrations in
humans at maximum daily dose (20mg q.i.d.) by more than 5017-fold. In the
presence of inhibition of the metabolism via CYP3A4 free plasma
concentrations of domperidone can rise up to 10-fold.
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