Neuromuscular block by antibiotics: polymyxin B

Area of Science:

• Pharmacology
• Neuroscience

Background:

• Antibiotics can cause neuromuscular blockade.
• Polymyxin B (PXB) is an antibiotic with potential neuromuscular effects.

Purpose of the Study:

• To characterize the neuromuscular block produced by Polymyxin B.
• To investigate the antagonism of PXB-induced block by cholinesterase inhibitors and calcium.

Main Methods:

• Sciatic nerve-tibialis anterior muscle preparations in anesthetized cats.
• Determination of ED50 and ED95 for PXB.
• Assessment of recovery time and train-of-four responses.
• Evaluation of antagonism by edrophonium, neostigmine, pyridostigmine, and calcium.

Main Results:

• The ED50 and ED95 of PXB were determined.
• Spontaneous recovery from block averaged 72 minutes.
• Cholinesterase inhibitors showed weak antagonism at low doses and enhancement at high doses.
• Calcium partially antagonized the neuromuscular block.

Conclusions:

• Neuromuscular blocks induced by antibiotics, like Polymyxin B, differ from those caused by other agents.
• The mechanism of PXB neuromuscular blockade is distinct and requires further investigation.