Atracurium Besylate
Atracurium is a highly utilized **nondepolarizing neuromuscular blocking agent** used primarily as an adjunct to general anesthesia. It provides profound skeletal muscle relaxation to facilitate surgical procedures, endotracheal intubation, and mechanical ventilation. **Key Clinical Pearls:** * **Organ-Independent Elimination:** Atracurium undergoes Hofmann elimination and ester hydrolysis, making it exceptionally valuable for patients with significant renal or hepatic disease. * **No Analgesia or Sedation:** It paralyzes the patient but provides absolutely zero pain relief or unconsciousness. It must *never* be used as a sole agent. * **Cardiovascular Stability:** At standard doses, it exhibits minimal cardiovascular effects compared to older neuromuscular blockers, though it can occasionally trigger histamine release. * **Species Sensitivity:** It is notably more potent in horses than in other species.
Mecanismo: Atracurium acts by competitively binding to **nicotinic cholinergic receptors** at the motor end-plate of the neuromuscular junction. By occupying these receptors, it prevents **acetylcholine (ACh)** from binding → inhibits depolarization of the muscle cell membrane → results in flaccid paralysis of skeletal muscles. Because it is a competitive antagonist, its effects can be reversed by increasing the concentration of ACh at the neuromuscular junction (e.g., by administering acetylcholinesterase inhibitors like neostigmine or edrophonium).
Dosificación por especie
- Induction dose · 0.22 mg/kg IV · IV · Single dose · Give 1/10th to 1/6th of this dose initially as a 'priming' dose, followed 4-6 minutes later with the remainder and a sedative/hypnotic agent.
- Intraoperative dose · 0.11 mg/kg IV · IV · As needed
- Induction of respiratory muscle paralysis during mechanical ventilation · Loading dose: 0.2-0.5 mg/kg IV, then a constant rate infusion 5 minutes later of 0.37 micrograms/kg/min · IV · CRI · Use D5W or 0.9% sodium chloride for diluent; do not mix with other drugs.
- Critically ill patients when low concentrations of, or no inhalant anesthesia can be used · 0.2 mg/kg IV initial dose; subsequent doses 0.1 mg/kg IV · IV · every 20-30 minutes · Do not dose more frequently than every 20-30 minutes unless a peripheral nerve stimulator is applied. Positive pressure ventilation required.
- Intraoperative dose · 0.055 mg/kg IV · IV · As needed · Note: ARCI UCGFS Class 2 Drug. Atracurium is more potent in horses than in other species.
- Paralysis for periophthalmic surgery (Rabbits) · 0.1 mg/kg · IV · Single dose
- Critically ill patients when low concentrations of, or no inhalant anesthesia can be used · 0.2 mg/kg IV initial dose; subsequent doses 0.1 mg/kg IV · IV · every 20-30 minutes · Do not dose more frequently than every 20-30 minutes unless a peripheral nerve stimulator is applied, or voluntary movement is observed. Positive pressure ventilation required.
Vías de administración
Contraindicaciones
- Hypersensitivity to atracurium
- Relative contraindication: Myasthenia gravis
- Lack of ventilatory support (must have mechanical ventilation available)
Efectos adversos
- Allergic reactions
- Inadequate or prolonged neuromuscular block
- Hypotension
- Vasodilation
- Bradycardia
- Tachycardia
- Dyspnea
- Bronchospasm
- Laryngospasm
- Rash
- Urticaria
- Injection site reaction
Interacciones farmacológicas
- Aminoglycoside antibiotics (e.g., gentamicin) · May enhance the neuromuscular blocking activity of atracurium
- General anesthetics (enflurane, isoflurane, halothane, sevoflurane) · May enhance and prolong the neuromuscular blocking activity
- Bacitracin, Polymyxin B (systemic) · May enhance neuromuscular blocking activity
- Procainamide · May enhance neuromuscular blocking activity
- Quinidine · May enhance neuromuscular blocking activity
- Lithium · May enhance neuromuscular blocking activity
- Magnesium salts · May enhance neuromuscular blocking activity
- Anticonvulsants (Phenytoin, Carbamazepine) · Reported to decrease both the effects and duration of neuromuscular blockade
- Other muscle relaxant drugs · May cause a synergistic or antagonistic effect
- Succinylcholine · May speed the onset of action and enhance the neuromuscular blocking actions of atracurium. Do not give atracurium until succinylcholine effects have diminished.
Monitoreo
- Level of neuromuscular blockade (recommend use of a peripheral nerve stimulator to evaluate 'train of 4' twitches)
- Spontaneous ventilation and voluntary muscle movement (if nerve stimulator is unavailable)
- Cardiac rate and blood pressure
- Core body temperature and acid-base status (can affect drug metabolism)
Sobredosis
Overdosage increases the risks of **hypotension**, **histamine release**, and **prolonged duration of muscle blockade**. Overdose possibilities can be minimized by monitoring muscle twitch responses to peripheral nerve stimulation. **Treatment:** * Treat conservatively with mechanical ventilation, oxygen, and IV fluids. * **Reversal of blockade:** May be accomplished by administering an anticholinesterase agent such as **edrophonium** (0.5 mg/kg IV) or **neostigmine** (0.02-0.04 mg/kg IV) combined with an anticholinergic (**atropine** or **glycopyrrolate**) to prevent severe bradycardia. * Reversal is usually complete within 8-10 minutes. Because the duration of action of atracurium may be longer than the reversal agent, careful observation is required, and readministration of the reversal agent may be necessary.
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