Effects of neostigmine, edrophonium, 4-aminopyridine and their combinations.

A study was carried out in the in-vitro rat phrenic nerve hemidiaphragm preparation to find a fast and strong working antagonist of non-depolarizing muscle relaxants. We studied neostigmine, edrophonium, 4-aminopyridine and their combinations from the cumulative concentration response curves of pancuronium. Neostigmine, edrophonium and 4-aminopyridine all antagonized the effect of pancuronium. Neostigmine and 4-aminopyridine did potentiate each other as did neostigmine and edrophonium. The combination of edrophonium and 4-aminopyridine showed less total effect than the addition of their individual effect. We conclude that the mechanisms of action of neostigmine and edrophonium are different.