The
incidence of central adverse effects may be increased following the concurrent use of
lidocaine and
phenytoin. Sinoatrial arrest has been reported in one patient receiving the combination.
Lidocaine levels may be reduced by
phenytoin. Fosphenytoin, a prodrug of
phenytoin, may interact similarly.
The
clinical significance of this interaction is most likely to be small. However, the arrest emphasises the need to exercise caution when giving two drugs that have cardiodepressant actions.