The neuromuscular blocking activity of a new aminoglycoside antibiotic netilmicin sulphate (SCH 20569)

The neuromuscular blocking activity of netilmicin sulphate (Sch 20569), a new aminoglycoside antibiotic, was studied on the rat sciatic nerve-gastrocnemius muscle preparation. The i.v. administration of netilmicin caused a gradual fall, up to complete blockade, of the muscular contraction elicited by nerve stimulation. Conversely, the muscular response to direct stimulation was not affected. The response pattern was similar to that seen with known aminoglycoside antibiotics. The acute toxic effects (LD50 i.p. in mice) of netilmicin were antagonized by pretreatment with neostigmine; this latter partially prevented netilmicin-induced blockade, but was not able to reverse it. Calcium chloride was the only agent effective both to prevent and to reverse the neuromuscular blocking effects of netilmicin.