• Volatile anesthetics: dose-dependent potentiation of all muscle relaxants; impact on initial dose of muscle relaxant may be greater with sevoflurane or desflurane, reflecting rapid equilibration of these poorly soluble drugs
• Local anesthetics potentiate effects of all muscle relaxants
• Nondepolarizing muscle relaxants: depending on the combination, produce synergistic or additive effects; clinical significance is doubtful
• Nondepolarizing–depolarizing muscle relaxants: response depends on the sequence; administering a nondepolarizer before SCh interferes with SCh blockade, and administering a nondepolarizer after SCh is potentiated
• Antibiotics: aminoglycosides and polymyxins are most likely to potentiate muscle relaxants
• Anticonvulsants: resistance to nondepolarizing muscle relaxants
• Magnesium: antagonizes the effect of calcium on release of ACh
• Metoclopramide: inhibits plasma cholinesterase and prolongs action of SCh and rocuronium

ACh = acetylcholine; SCh = succinylcholine.