Description

Atracurium besylate is a non-depolarizing neuromuscular blocking agent (NMBA). It is a skeletal muscle relaxant used in clinical anesthesia and intensive care settings. It is administered intravenously and is known for its intermediate duration of action. A key feature of atracurium is its unique metabolic pathway, as it is degraded in the body independently of liver and kidney function, making its use more predictable in patients with organ dysfunction.

Indication

Atracurium besylate is indicated as an adjunct to general anesthesia. Its primary uses are to:

• Facilitate Tracheal Intubation: It provides rapid and complete relaxation of the laryngeal and pharyngeal muscles, allowing for the easy insertion of a breathing tube into the trachea.

• Provide Skeletal Muscle Relaxation During Surgery: It is used to achieve skeletal muscle paralysis during various surgical procedures, which is essential for the surgeon to have a still and relaxed field of operation.

• Assist in Mechanical Ventilation: It can be used in the intensive care unit (ICU) to provide muscle relaxation in patients who require mechanical ventilation, particularly in those with severe respiratory failure, to ensure patient-ventilator synchrony.

Mechanism of Action

Atracurium’s mechanism of action is based on its ability to block the transmission of nerve impulses at the neuromuscular junction, leading to skeletal muscle paralysis.

1. Neuromuscular Junction: The neuromuscular junction is the site where a motor nerve fiber communicates with a skeletal muscle fiber. The nerve releases a neurotransmitter called acetylcholine (ACh).

2. Competitive Antagonism: Atracurium acts as a competitive antagonist at the nicotinic acetylcholine receptors on the motor end plate of the muscle fiber. It has a similar shape to acetylcholine but does not activate the receptor. Instead, it binds to the receptor, occupying the site where acetylcholine would normally bind.
3. Prevention of Muscle Contraction: By blocking the receptors, atracurium prevents acetylcholine from binding and initiating the depolarization of the muscle cell membrane. This prevents the muscle fiber from contracting, resulting in flaccid paralysis of the skeletal muscles.

4. Unique Metabolism (Hofmann Elimination and Ester Hydrolysis): The unique feature of atracurium is its dual elimination pathway:

• • Hofmann Elimination: This is a spontaneous, non-enzymatic chemical degradation that occurs at physiological pH and temperature. The drug simply breaks down on its own without the need for an enzyme.

• • Nonspecific Ester Hydrolysis: The drug is also broken down by non-specific plasma esterases in the blood. This combination of degradation pathways ensures that the drug’s metabolism and elimination are independent of liver or kidney function, providing a predictable duration of action and making it a safe choice for patients with organ dysfunction.