AKA
Anectine® or Quelicin®


Classification:
Musculoskeletal Agents
Skeletal Muscle Relaxants
Neuromuscular blockers

Description: Succinylcholine chloride is an ultra short-acting, depolarizing-type, skeletal muscle relaxant for intravenous administration. It is the neuromuscular blocking agent with the fastest onset time and allows endotracheal intubation within 60 seconds. Succinylcholine may induce vagal stimulation and has histamine-releasing properties. Due to rare reports of ventricular dysrhythmias and cardiac arrest in pediatric patients, the use of succinylcholine in children is reserved for emergency intubation or in instances where the airway must be secured immediately. Succinylcholine can also be administered intramuscularly, which may become important for use in children when emergency control of the airway is necessary and there is no IV access. Succinylcholine was approved by the FDA in 1952.

Mechanism of Action: Succinylcholine (suxamethonium) is a depolarizing skeletal muscle relaxant. It competes with acetylcholine for the cholinergic receptors of the motor endplate, and, like acetylcholine, it combines with these receptors to produce depolarization. Succinylcholine, however, causes a more prolonged depolarization than acetylcholine because it has a high affinity for the cholinergic receptor and a strong resistance to acetylcholinesterase. Depolarization results in fasciculation of the skeletal muscles followed by muscle paralysis. Neuromuscular transmission is inhibited as long as an adequate concentration of succinylcholine remains at the receptor site.

The paralysis following succinylcholine administration is selective. Initially, paralysis involves the levator muscles of the face and muscles of the glottis. Paralysis consecutively involves the intercostals, the diaphragm, and all other skeletal muscles. Recovery of muscles generally occurs in the reverse order.

Pharmacokinetics: Succinylcholine is poorly absorbed from the gastrointestinal tract, but when administered intravenously, it has a rapid onset and a short duration of action. Following IV administration of 10—30 mg to healthy adults, complete muscle relaxation occurs in 0.5—1 minute. This effect persists for 2—3 minutes and gradually dissipates within 10 minutes. After IM injection, muscle relaxation occurs in 2—3 minutes and persists for 10—30 minutes. Patients with low pseudocholinesterase concentrations may experience longer durations of action.

After IV administration, succinylcholine is distributed in the extracellular fluid and rapidly reaches its site of action at the motor endplate of the myoneural junction. Following an intravenous bolus dose of 1 or 2 mg/kg, succinylcholine serum concentrations are below the detection limit (<2 ug/mL) after 2.5 minutes. Because it is highly ionized and has low fat solubility, succinylcholine does not readily cross the placenta.

Up to 10% of a succinylcholine dose is excreted unchanged in the urine. The remainder of a dose is rapidly hydrolyzed by plasma pseudocholinesterase to succinlymonocholine and choline. Succinylmonocholine possesses nondepolarizing muscle-relaxant properties. Succinylmonocholine is excreted partly in urine; the remainder is broken down by alkaline hydrolysis to the inactive metabolites succinate and choline. Hydrolysis of succinylmonocholine occurs relatively slowly, so succinylmonocholine can accumulate and cause prolonged apnea, especially in patients with impaired renal function.