According to Miller, potency of a NMBD is best described as the effective dose – “The dose of a neuromuscular blocking drug required to produce an effect (e.g., 50%, 90%, or 95% depression of twitch height, commonly expressed as ED50, ED90, and ED95, respectively“. Thus, the ED95 is the amount of NMBD required to reduce twitch height by 95%.
ED95 (mg/kg) of Commonly used NMBDs (Adapted from Table 29-4 in Miller)
- Rocuronium: 0.31 (0.6-1 mg/kg induction, 1.9 to 3.2x the ED95)
- Vecuronium: 0.04 (0.1 mg/kg induction, 2.5x the ED95)
- Pancuronium: 0.07 (0.1 mg/kg induction, 1.4x the ED95)
- Cisatracurium: 0.04 (0.2 mg/kg induction, 5x the ED95, onset in 2.8 mins (Ref. 1)
Note that the reason that rocuronium onset is so rapid is that it is not very potent, thus high concentrations (10-fold higher than for vecuronium and pancuronium) are required.
References
- L S Bluestein, L W Stinson, R L Lennon, S N Quessy, R M Wilson Evaluation of cisatracurium, a new neuromuscular blocking agent, for tracheal intubation. Can J Anaesth: 1996, 43(9);925-31 PubMed Link
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