Effects of SZ1677, a new non-depolarizing steroidal neuromuscular blocking drug, and rocuronium on two laryngeal muscles and the anterior tibial muscle in guinea pigs.
BACKGROUND
SZ1677 is a new neuromuscular blocking drug structurally related to rocuronium. We compared the effect of an ED(90) of SZ1677 (25 microg/kg) with that of rocuronium (100 microg/kg) in guinea pig laryngeal and peripheral muscles.


METHODS
Electromyography was used to quantify neuromuscular blockade at the posterior cricoarytenoid muscle, the thyroarytenoid muscle and the anterior tibial muscle after SZ1677 (n = 10) and rocuronium (n = 9).


RESULTS
Maximum neuromuscular blockade was similar after SZ1677 and rocuronium (83 +/- 11% vs. 89 +/- 11%; thyroarytenoid muscle: 91 +/- 8% vs. 97 +/- 3%; anterior tibial muscle: 91 +/- 15% vs. 96 +/- 3%, respectively). Onset time of neuromuscular blockade at the laryngeal muscles was similar for the two neuromuscular blocking drugs; it was shorter at the thyroarytenoid muscle (67 +/- 32 s vs. 42 +/- 40 s) than at the posterior cricoarytenoid muscle (101 +/- 26 s vs. 102 +/- 108 s). Onset time at the anterior tibial muscle was longer after SZ1677 (114 +/- 34 s) than after rocuronium (68 +/- 46 s); P < 0.05. Neuromuscular recovery was faster after SZ1677 (interval 25%-75%: posterior cricoarytenoid muscle: 222 +/- 66 s; thyroarytenoid muscle: 192 +/- 92 s; tibial muscle 149 +/- 55 s) than after rocuronium (450 +/- 148 and 464 +/- 183 s, 292 +/- 86 s, respectively); P < 0.05.


CONCLUSIONS
In guinea pigs, SZ1677 offers a rapid onset of neuromuscular blockade at a laryngeal adductor muscle with a shorter duration than rocuronium. Regardless of the drug used, the course of neuromuscular blockade differs not only between peripheral muscles and the larynx but also between antagonistic laryngeal muscles. The differences seem to be species specific.
Department of Anaesthesia and General Intensive Care (B), Medical University of Vienna, Vienna, Austria. andrea.michalek-sauberer@meduniwien.ac.at
A
A
Michalek-Sauberer
E M
EM
Nicolakis
E S
ES
Vizi
H
H
Gilly
D000731:Androstanes / Q000494:pharmacology*; D000732:Androstanols / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D004576:Electromyography; D006168:Guinea Pigs; D006614:Hindlimb; D007821:Laryngeal Muscles / Q000187:drug effects* / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D019148:Neuromuscular Blockade; D003473:Neuromuscular Nondepolarizing Agents / Q000494:pharmacology*; D012009:Recurrent Laryngeal Nerve / Q000187:drug effects / Q000502:physiology; D000077123:Rocuronium; D012584:Sciatic Nerve / Q000187:drug effects / Q000502:physiology
C458501:1-(3-hydroxy-17-acetyloxy)-2-(1.4-dioxa-8-azaspiro-(4,5)-dec-8-yl)-(5alpha-androstane-16-yl)-1-(2-propenyl) pyrrolidine; D000731:Androstanes; D000732:Androstanols; D003473:Neuromuscular Nondepolarizing Agents; D000077123:Rocuronium