Atracurium differs from cis-atracurium primarily in what aspect?

Atracurium differs from cis-atracurium primarily in what aspect?

• A. Molecular weight
• B. Formation of laudanosine
• C. Histamine release
• D. No renal metabolism

Answer: (C)

The main point here is histamine release potential. Atracurium can release histamine when given, which can lead to hypotension, flushing, and sometimes tachycardia, especially with rapid administration or higher doses. Cis-atracurium, on the other hand, is the purer isomer and is much less likely to provoke histamine release, making it safer in patients where a drop in blood pressure would be problematic. The two drugs share other pharmacologic features: both are broken down by Hofmann elimination and ester hydrolysis rather than by hepatic metabolism, and neither relies on renal metabolism to an appreciable extent. A related, secondary point is that laudanosine is a metabolite produced during degradation of atracurium and is formed in smaller amounts with cis-atracurium; however, this is less clinically impactful than the histamine-related effects. So the key difference that most strongly affects practice is the propensity to release histamine and the consequent hemodynamic effects.

The main point here is histamine release potential. Atracurium can release histamine when given, which can lead to hypotension, flushing, and sometimes tachycardia, especially with rapid administration or higher doses. Cis-atracurium, on the other hand, is the purer isomer and is much less likely to provoke histamine release, making it safer in patients where a drop in blood pressure would be problematic.

The two drugs share other pharmacologic features: both are broken down by Hofmann elimination and ester hydrolysis rather than by hepatic metabolism, and neither relies on renal metabolism to an appreciable extent. A related, secondary point is that laudanosine is a metabolite produced during degradation of atracurium and is formed in smaller amounts with cis-atracurium; however, this is less clinically impactful than the histamine-related effects.

So the key difference that most strongly affects practice is the propensity to release histamine and the consequent hemodynamic effects.