Accelerated recovery from doxacurium-induced neuromuscular blockade in patients receiving chronic anticonvulsant therapy.

STUDY OBJECTIVE

To determine whether a drug interaction exists between doxacurium and anticonvulsants.

DESIGN

Open-label controlled study.

SETTING

Inpatient neuroanesthesiology service at a university medical center.

PATIENTS

Three groups of nine patients each, consisting of those chronically receiving carbamazepine, phenytoin, or no anticonvulsant therapy.

INTERVENTION

Intravenous administration of doxacurium 60 micrograms/kg during anesthesia with nitrous oxide (N2O), fentanyl, and droperidol.

MEASUREMENTS AND MAIN RESULTS

The adductor pollicis mechanical response to single 0.2-millisecond supramaximal pulses delivered to the ulnar nerve at 0.15 Hz was recorded. Patients receiving phenytoin or carbamazepine recovered neuromuscular function more quickly than did the control group. The times from doxacurium injection to 50% recovery of mechanomyographic response, for example, were as follows: control group, 161 +/- 55 minutes (mean +/- SD); phenytoin group, 76 +/- 31 minutes; and carbamazepine group, 66 +/- 27 minutes (p less than 0.05). The time for recovery from 75% to 25% blockade (recovery index) was decreased by 53% in the phenytoin group and by 67% in the carbamazepine group as compared with the control group (41.0 +/- 18.0 minutes and 28.6 +/- 8.6 minutes vs 86.4 +/- 45.2 minutes, respectively).

CONCLUSION

Chronic treatment with anticonvulsants results in more rapid recovery from neuromuscular blockade produced by doxacurium.