Dose-dependent pharmacokinetic behavior of lidocaine in the conscious dog

The apparent steady state blood concentration of lidocaine in dogs depends on the animal's lidocaine treatment history. For example, an infusion of 50 microgram/Kg/min X 240 min followed immediately by an infusion of 125 microgram/Kg/min X 240 min yields steady state lidocaine levels which are consistent with a linear drug dispositional system. However, when the sequence of these infusions is reversed the apparent steady state level during the low infusion rate step is much greater than those predicted from the steady state level observed during the high infusion rate (assuming a linear dispositional model). These data suggest that high dose lidocaine infusion treatment alters the dog's ability to clear lidocaine during a subsequent low infusion rate treatment period.