Lidocaine Famotidine

Some studies suggest that both cimetidine and ranitidine can raise plasma bupivacaine levels, whereas other evidence suggests that no significant interaction occurs. Ranitidine does not appear to significantly affect lidocaine. Some studies found that cimetidine does not affect lidocaine when used as an anaesthetic. Other studies found that cimetidine increased plasma lidocaine levels and that famotidine had less effect. See also Lidocaine + H2-receptor antagonists , p.264 for interactions of lidocaine used as an an-tiarrhythmic. 

A confusing situation. No clinically important interaction has been established, but be alert for any evidence of increased bupivacaine toxicity resulting from raised total plasma levels and rises in unbound bupivacaine levels during the concurrent use of cimetidine and possibly ranitidine. Cimetidine (but not ranitidine) has been shown to raise plasma lidocaine levels when lidocaine is used as an antiarrhythmic (see Lidocaine + H2-receptor antagonists , p.264), but some of the studies cited above found cimetidine did not affect lidocaine levels when lidocaine is used as an anaesthetic. However, in the studies comparing the effects of cimetidine and famotidine, cimetidine was found to increase lidocaine levels and it was suggested that famotidine may be preferable to cimetidine as pretreatment before epidural lidocaine. ... 

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