The new neuromuscular blocking agents: do they offer any advantages?

Area of Science:

• Pharmacology
• Anesthesiology
• Drug Development

Background:

• Aminosteroid neuromuscular blocking drugs like rapacuronium bromide and rocuronium bromide are crucial in anesthesia.
• Emerging drug classes, including bis-tetrahydroisoquinolinium chlorofumarates and tropinyl diester derivatives, offer new neuromuscular blocking properties.
• Comparative analysis with existing agents such as mivacurium and cisatracurium is essential for understanding their clinical utility.

Purpose of the Study:

• To review the pharmacodynamics and pharmacokinetics of rapacuronium bromide and rocuronium bromide.
• To introduce and compare two novel classes of neuromuscular blocking agents: bis-tetrahydroisoquinolinium chlorofumarates and tropinyl diester derivatives.
• To provide a comparative overview of these agents against mivacurium and cisatracurium.

Main Methods:

• Pharmacodynamic and pharmacokinetic data analysis of rapacuronium bromide and rocuronium bromide.
• Introduction of new drug classes: bis-tetrahydroisoquinolinium chlorofumarates and tropinyl diester derivatives.
• Comparative assessment of efficacy, onset, duration, recovery, and side effect profiles.

Main Results:

• Rapacuronium bromide (1.5 mg kg⁻¹) achieves maximal block in 54s, with recovery to train-of-four ratio 0.7 in 20 min post-neostigmine. Its clearance is 7-8 ml kg⁻¹ min⁻¹, with hepatic metabolism and no reported effect prolongation in renal/hepatic failure.
• Rocuronium bromide (2xED95) provides rapid block onset (1 min) but slower spontaneous recovery (>40 min). Clearance is 4 ml kg⁻¹, with altered pharmacodynamics in renal/hepatic disease and reported anaphylactoid reactions.
• The bis-tetrahydroisoquinolinium chlorofumarate GW280430A shows rapid onset and short duration (8-9 min), with no apparent adverse cardiovascular or respiratory effects. Tropinyl diester derivative G-1-64 demonstrates fast onset and short recovery (5-7 min), with reported vagal block.

Conclusions:

• Rapacuronium bromide offers rapid onset and recovery, with favorable profiles in renal/hepatic impairment, though its metabolite Org 9488 may limit prolonged use.
• Rocuronium bromide provides fast onset but slower recovery, with altered pharmacokinetics in organ dysfunction and recent reports of anaphylactoid reactions.
• Newer agents like GW280430A and G-1-64 show promise with rapid onset and short durations, potentially offering improved safety profiles, though further research is needed.