Influence of aprotinin (Trasylol) on the action of suxamethonium.

Aprotinin concentrations such as occur in vivo after intravenous injection of 100,000 KIU, inhibit ChE activity by about 5-16 per cent. The degree of inhibition is greatest between 6 and 20 minutes post-injection and is negligible after 30 minutes. When the ChE baseline activity is normal, 5-16 per cent inhibition does not lead to a prolongation of the action of suxamethonium. A prolongation of the apnoeic period in connection with an administration of aprotinin is only possible if the ChE activity is close to the critical level and is lowered by aprotinin to a range in which the breakdown of suxamethonium is delayed. There is no reason to dispense with aprotinin in operations in which suxamethonium has been given or must be given. Aprotinin could lead to a lowering below the critical threshold only in those patients who have a pathologically depressed ChE activity level and therefore are already predisposed to prolonged apnoea after suxamethonium.