resistance to NMB

Case; 58 years old male with history of seizures is admitted to ICU with aspiration pneumonia requiring mechanical ventilation along with sedation and neuro-muscular blockade (NMB). Despite high dose of Nimbex (Cisatracurium), adequate NMB cannot be achieved. 

Answer: Anticonvulsant and Cisatracurium-induced neuromuscular blockade interaction 

Anticonvulsants are known to interact with Cisatracurium-induced neuromuscular blockade, particularly carbamazepine. Carbamazepine not only increases the clearance of cisatracurium but also increases the resistance to the neuromuscular blocking effect of cisatracurium. Higher doses of cisatracurium may be required in patients on chronic carbamazepine therapy. 

A similar effect has been reported with phenytoin. #pharmacology 

References: 

1. Richard A, Girard F, Girard DC, Boudreault D, Chouinard P, Moumdjian R, Bouthilier A, Ruel M, Couture J, Varin F. Cisatracurium-induced neuromuscular blockade is affected by chronic phenytoin or carbamazepine treatment in neurosurgical patients. Anesth Analg. 2005 Feb;100(2):538-544. doi: 10.1213/01.ANE.0000143333.84988.50. PMID: 15673889. 

2. Koenig MH, Edwards LT. Cisatracurium-induced neuromuscular blockade in anticonvulsant treated neurosurgical patients. J Neurosurg Anesthesiol. 2000 Oct;12(4):314-8. doi: 10.1097/00008506-200010000-00003. PMID: 11147379.