[The effects of intravenous and intraperitoneal dexamethasone treatment on vecuronium in the anesthetized rat]

It is fairly widespread clinical practice to administer large doses of corticosteroids to patients in cases of shock; doses of hydrocortisone as high as 50 mg/kg given intravenously have been proposed and used; especially in cases of Myasthenia Gravis. Its effects on neuromuscular transmission is not yet fully understood. In order to determine the mechanism of this interaction, we undertook this investigation. The neuromuscular effects of Dexamethasone, at single dose of 100 micrograms/kg intravenously or intraperitoneally, were studied by electromyographical quantification of the tibialis-anterior muscle evoked by sciatic nerve stimulation in 21 rats anesthetized with Urothane 1.25 g/kg given intraperitoneally. Intravenous Dexamethasone (n = 7) had no obvious effect on the blockade of tibialis-anterior muscle produced by the cumulative doses of Vecuronium (ED50 = 180 +/- 24 micrograms/kg), as compared with the control group (n = 7) (ED50 = 201 +/- 18 micrograms/kg). In contrast, intraperitoneal Dexamethasone (n = 7) produced a significant (P < 0.05) change (ED50 = 240 +/- 28 micrograms/kg), when compared with control group. The results showed that in tibialis-anterior muscle sciatic nerve preparation of rats, intraperitoneal Dexamethasone had antagonism effect on Vecuronium. However, there was no obvious influence on Vecuronium in the intravenous Dexamethasone group.