Succinylcholine and Rocuronium
This contribution was originated by Matthew Soto.
Rocuronium is an intermediate acting agent with rapid onset and is of lower potency.
If an agent is longer acting, it is usually more potent, and would subsequently need to be administed in low concentrations. Use of low concentrations of drug can effectively delay drug onset of action.
Similarly, if an agent is shorter acting and of lower potency, it would need to be administered in higher concentrations. Drugs administered in higher concentrations tend to have a short time to onset of drug action.
Thus, Rocuronium is an alternative to Succinylcholine; which is often used as the benchmark for rapid onset paralytics.
Succinylcholine has a time to onset of 1 to 1.5 minutes and a typical clinical duration of action around 5 to 8 minutes. The drug is eliminated via hydrolysis in plasma by cholinesterases.
Order of Paralysis:
Glottis & Facial levator muscles --> Intercostals --> Diaphragm --> other skeletal muscles
Order of Recovery: Skeletal muscles --> Diaphragm --> Intercostals --> Glottis & Facial levator muscles
Rocuronium has a time to onset of 1 to 2 minutes and a somewhat more lengthy duration of 30 to 60 minutes. Rocuronium is cleared hepatically.
Order of Paralysis:
Fine movement (Eyes, face & neck) --> Limbs, Chest & Abdomen --> Diaphragm
Order of Recovery: Diaphragm --> Limbs, Chest & Abdomen --> Fine movement (Eyes, face & neck)
ADVERSE DRUG REACTIONS*
SUCCINYLCHOLINE AV Block Bradycardia (greater in peds than in adults) Cardiac Arrest Flushing (from histamine release) Hyperkalemia (depolarizing agents release K from intracellular spaces – can be life threatening) Hypersalivation (from histamine release) Myalgia (from muscle fasciculations)
Myoglobinuria Ocular Hypertension Premature Atrial contractions Premature Ventricular Contractions Renal tubual obstruction Rhabdomyolysis Tremor Urticaria (from histamine release) Weakness
ROCURONIUM Hiccups Injection Site Reaction (Primarily Edema) Nausea/Vomiting
PHARMACOKINETICS At physiologic pH, Succinylcholine is highly ionized due to the presence of two quaternary amine groups. This yields a drug species that is poorly distributed in fat. Thus, Succinylcholine kinetics is best represented by a one-compartment model.
Adverse effects were obtained from Clinical Pharmacology 2007
Free simulations of succinylcholine and rocuronium pharmacokinetics - registration (which is also free) is required to access these free simulations.