The effect of levodopa on halothane anesthetic requirements

Acute and chronic levodopa (L-dopa) administration alters halothane minimum alveolar concentration (MAC) in dogs. L-dopa 5, 10, and 25 mg./kg. intravenously (I.V.) reduced halothane MAC 15, 20, and 25 percent, respectively, 1 hour after injection, with return toward normal after 3 hours. Fifty mg./kg. increased halothane MAC 40 percent at 1 hour, but produced at 30 percent decrease from control MAC at 3 hours. Two groups of 4 dogs each given oral L-dopa in doses increasing from 50 mg./kg. daily the 1st week to 300 mg./kg. daily the 5th week, decreased MAC an insignificant 9.5 plus or minus 25.2 percent at 4 hours after the last dose and increased MAC 3.5 plus or minus 7.3 percent at 12 hours after the last dose. A small, insignificant decrease of 9 percent in MAC was measured in 4 dogs given I.V. L-dopa 25 mg./kg. q.i.d for 4 days.