Can neostigmine be used as an alternative to the edrophonium (Tensilon) test?

From the Guidelines

Neostigmine can be used as an alternative to the edrophonium test for diagnosing myasthenia gravis, as it inhibits acetylcholinesterase and increases acetylcholine availability at the neuromuscular junction, temporarily improving muscle strength in myasthenia gravis patients 1. To perform a neostigmine test, administer 0.02 mg/kg of neostigmine intramuscularly (typically 1.5-2 mg for adults), along with 0.01 mg/kg of atropine (usually 0.4-0.6 mg) to counteract cholinergic side effects. Some key points to consider when using neostigmine as an alternative to the edrophonium test include:

• The dose of neostigmine required to obtain a TOF ratio > 0.7 is in the range of 40 to 50 mg/kg 1
• Neostigmine has a slower onset (10-30 minutes) but longer duration (2-4 hours) compared to edrophonium, which has a rapid onset (30 seconds) and short duration (5-10 minutes)
• Neostigmine is particularly useful when more time is needed to evaluate complex or subtle symptoms
• Monitor for potential side effects including bradycardia, hypotension, increased secretions, and gastrointestinal disturbances, even with atropine pretreatment 1. It is essential to note that the provided evidence does not directly compare neostigmine and edrophonium for diagnosing myasthenia gravis, but neostigmine's mechanism of action and its use in reversing neuromuscular blockade make it a viable alternative. The most recent and highest quality study on the topic is from 2024, which discusses the use of neostigmine in anaesthesia, but does not directly address its use in diagnosing myasthenia gravis 1. However, based on the available evidence and the mechanism of action of neostigmine, it is recommended to use neostigmine as an alternative to the edrophonium test for diagnosing myasthenia gravis, with careful monitoring of potential side effects.

From the Research

Neostigmine as an Alternative to Edrophonium

• Neostigmine and edrophonium are both used to antagonize neuromuscular block, but they have different characteristics 2, 3, 4, 5, 6.
• Edrophonium has a faster onset of action compared to neostigmine, but its duration of action is equivalent to or shorter than that of neostigmine 2, 3, 5.
• Neostigmine is more potent than edrophonium, with a higher potency ratio of 16:1 when used to antagonize pancuronium 6.
• The effectiveness of neostigmine and edrophonium as antagonists can vary depending on the type and degree of neuromuscular block, as well as the specific conditions of the study 3, 4, 5.

Comparison of Neostigmine and Edrophonium

• Edrophonium may be less effective than neostigmine in antagonizing moderate neuromuscular block induced by pancuronium or tubocurarine 4.
• Neostigmine may be more effective than edrophonium in achieving adequate recovery from neuromuscular block, especially when used to antagonize pipecuronium-induced block 3.
• Edrophonium may have an advantage over neostigmine in terms of hemodynamic stability and reversal time when used to antagonize residual vecuronium-induced neuromuscular block 5.

Use of Neostigmine as an Alternative

• Neostigmine can be used as an alternative to edrophonium for the reversal of neuromuscular blockade, but the choice of antagonist may depend on the specific circumstances of the patient and the type of block being antagonized 2, 3, 4, 5, 6.
• The combination of edrophonium and neostigmine offers no advantage over the use of either drug alone 6.