Cimetidine modestly reduces the clearance of
intravenous lidocaine and raises its
serum levels (by about 30% within 6 hours in one study).
Lidocaine toxicity may occur if the dosage is not reduced. However, not all patients are affected.
Monitor all patients closely for evidence of
toxicity and, if possible, consider checking
serum lidocaine levels regularly. A reduced infusion rate may be needed. Ranitidine does not interact and so would appear to be a suitable alternative to
cimetidine.