Cisatracurium Besylate and Atracurium Besylate drug compounds are muscle relaxants which work by blocking the signals between nerves and muscles. These are used to maintain neuromuscular relaxation during surgical procedures and are usually administered before general anaesthesia in preparing a patient for surgery. Both are non-depolarizing neuromuscular blocking drugs (NMBDs) which are clinically used to ease procedures such as intubation or mechanical ventilation in the Intensive Care Unit (ICU).

Though both drugs have neuromuscular blocking effects identical to each other, the difference between Cisatracurium Besylate and Atracurium Besylate is that Cisatracurium is more potent and has significantly fewer side effects.

CISATRACURIUM BESYLATE

Pharmacodynamic properties

Cisatracurium is an intermediate-duration, non-depolarizing benzylisoquinolinium skeletal muscle relaxant. Cisatracurium binds to cholinergic receptors on the motor end-plate to antagonise the action of acetylcholine, resulting in a competitive block of neuromuscular transmission. This action is readily reversed by anticholinesterase agents such as neostigmine or edrophonium. The ED95 (dose required to produce 95% depression of the twitch response of the adductor pollicis muscle to stimulation of the ulnar nerve) of cisatracurium is estimated to be 0.05 mg/kg body weight during opioid anaesthesia (thiopentone/fentanyl/midazolam). The ED95 of cisatracurium in children during halothane anaesthesia is 0.04 mg/kg.

Pharmacokinetic properties

Cisatracurium undergoes degradation in the body at physiological pH and temperature by Hofmann elimination (a chemical process) to form laudanosine and the monoquaternary acrylate metabolite. The monoquaternary acrylate undergoes hydrolysis by non-specific plasma esterases to form the monoquaternary alcohol metabolite. Elimination of cisatracurium is largely organ independent but the liver and kidneys are primary pathways for the clearance of its metabolites. These metabolites do not possess neuromuscular blocking activity.

Storage

Cisatracurium Besylate injection should be refrigerated at 2° to 8°C (36° to 46°F) in the carton to preserve potency. Protect from light and do not freeze. Once removed from refrigeration to room temperature, storage conditions needed are 25°C/77°F. It should be used within 21 days, even if re-refrigerated.

ATRACURIUM BESYLATE

Pharmacodynamic Properties

Atracurium besylate antagonizes the neurotransmitter action of acetylcholine by binding competitively with cholinergic receptor sites on the motor end-plate. This antagonism is inhibited, and neuromuscular block reversed, by acetylcholinesterase inhibitors such as neostigmine, edrophonium, and pyridostigmine.

Atracurium can be used most advantageously if muscle twitch response to peripheral nerve stimulation is monitored to assess the degree of muscle relaxation.

The ED95 (dose required to produce 95% suppression of the muscle twitch response with balanced anaesthesia) has averaged 0.23 mg/kg (0.11 to 0.26 mg/kg in various studies). An initial atracurium dose of 0.4 to 0.5 mg/kg generally produces maximum neuromuscular block within 3 to 5 minutes of injection, with good or excellent intubation conditions within 2 to 2.5 minutes in most patients. Recovery from neuromuscular block (under balanced anaesthesia) can be expected to begin approximately 20 to 35 minutes after injection.

Underbalanced anaesthesia, recovery to 25% of control is achieved approximately 35 to 45 minutes after injection, and recovery is usually 95% complete approximately 60 to 70 minutes after injection. The neuromuscular blocking action of atracurium is enhanced in the presence of potent inhalation anaesthetics.

Pharmacokinetics Properties

Atracurium in humans is essentially linear within the 0.3 to 0.6 mg/kg dose range. The elimination half-life is approximately 20 minutes. This is consistent with the results of in vitro studies which have shown that atracurium is inactivated in plasma via two nonoxidative pathways: ester hydrolysis, catalyzed by nonspecific esterases; and Hofmann elimination, a nonenzymatic chemical process that occurs at physiological pH. Some placental transfer occurs in humans.

Storage

Atracurium Besylate injection should be refrigerated at 2°C to 8°C (36°F to 46°F) to preserve potency. Like cisatracurium, it must be protected from light and should not be frozen. Keep vials in carton until time of use. Upon removal from refrigeration to room temperature, storage conditions must be 25°C/77°F. Use Atracurium Besylate injection within 14 days even if re-refrigerated.

Scott-Edil Pharmacia Ltd., one of the best Indian pharmaceutical companies, manufactures Cisatracurium Besylate and Atracurium Besylate. For more details, visit Scott-edil.com.