Acetylcholinesterase inhibitors for myasthenia gravis: Nursing pharmacology

Definitions & Key takeaways

Acetylcholinesterase inhibitors are a class of drugs that are used to treat myasthenia gravis. These drugs work by inhibiting the action of acetylcholinesterase, an enzyme that breaks down the neurotransmitter acetylcholine. Acetylcholine is responsible for mediating muscle contraction. By inhibiting its breakdown, acetylcholinesterase inhibitors increase the amount of acetylcholine available for muscle contraction, which leads to improved muscle strength.

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Introduction0:00–0:26

Myasthenia gravis is an autoimmune disorder caused by antibodies that bind to and destroy acetylcholine receptors on the surface of skeletal muscle cells, resulting in fatigue and muscle weakness due to impaired muscle contractions.
Although there’s no cure, certain medications, called acetylcholinesterase inhibitors, can be used to help mitigate some of the symptoms and improve the client’s quality of life.Now, the most commonly used acetylcholinesterase inhibitors for myasthenia gravis are neostigmine and pyridostigmine.

Mechanism of action0:26–1:17

These medications can be administered orally, intravenously, or intramuscularly, while neostigmine can be also given subcutaneously to children.
Once absorbed into the bloodstream, acetylcholinesterase inhibitors travel to the skeletal muscles and inhibit the enzyme acetylcholinesterase, which normally breaks down the neurotransmitter acetylcholine.
As a result, these medications cause acetylcholine to build up in the synaptic cleft, causing its cholinergic effects to be increased and prolonged.
This helps counteract the effect of acetylcholine receptor antibodies, and ultimately results in improved muscle strength and contraction.However, increased acetylcholine levels can also cause cholinergic side effects, such as miosis, blurred vision, headaches, dizziness, and drowsiness.

Side effects1:17–2:13

At the same time, in the airways, acetylcholine triggers bronchoconstriction and increases bronchial secretions, which can lead to dyspnea and a persistent cough.In the cardiovascular system, acetylcholine reduces blood pressure and slows down the heart rate, which can result in hypotension, bradycardia, heart block, and even cardiac arrest.
In the gastrointestinal tract, these medications can cause increased motility and secretions, leading to increased salivation, nausea, vomiting, cramps, diarrhea, and involuntary defecation; and in the urinary tract, acetylcholine stimulates the bladder muscles and sphincter relaxation, which may cause a sense of urgency.
Finally, excessive cholinergic stimulation can lead to a cholinergic crisis, which can be managed with atropine. As far as contraindications go, acetylcholinesterase inhibitors should not be administered to clients with bradycardia, as well as in those with gastrointestinal or urinary obstruction.

Contraindications and cautions2:13–2:50

Acetylcholinesterase inhibitors should also be used with caution during pregnancy and breastfeeding, as well as in clients with a history of seizures.
Additional precautions should be taken in clients with asthma or chronic obstructive pulmonary disease, as well as in those with cardiovascular disease like arrhythmias, hyperthyroidism, and in clients with gastrointestinal disease like peptic ulcer.
Now, if a client with myasthenia gravis is prescribed an acetylcholinesterase inhibitor like neostigmine, first, perform a baseline assessment, including vital signs and their current symptoms, including fatigue, eyelid drooping, vision problems, peripheral muscle weakness, as well as any difficulty breathing or swallowing.

Nursing considerations & client education2:50–5:08

Next, review their most recent laboratory test results, specifically renal and liver function; and diagnostic test results, including electromyography, or EMG, Tensilon test, and pulmonary function tests.
Next, explain to your client how the medication will help improve their muscle strength and decrease their fatigue. Instruct them to take their medication three times daily on an empty stomach, either 1 hour before or 2 hours after a meal.
For maximum medication effect, stress the importance of taking their medication consistently, on a regular schedule. Encourage your client to keep a record of when they take their medication, as well as their symptoms before and after administration.
Also, be sure your client can recognize if the prescribed dose is insufficient to control their symptoms, which could result in a myasthenic crisis.
If their symptoms don’t improve or get worse, prompt your client to notify their healthcare provider so dosage adjustments can be individualized.
Then, teach your client how to recognize symptoms of excessive cholinergic stimulation that can lead to a cholinergic crisis, including diaphoresis, diarrhea, urinary urgency, bradycardia, bronchospasm, cough, or dyspnea, as well as excessive lacrimation and salivation.
Stress the importance of immediately seeking medical attention if they experience these symptoms. In addition, prompt your client to seek medical attention immediately should they experience symptoms like extreme muscle weakness, as well as difficulty speaking or breathing.
Lastly, teach your client to wear medical alert identification at all times. Finally, during treatment with an acetylcholinesterase inhibitor like neostigmine, be sure to monitor for the development of side effects, especially signs and symptoms of excessive cholinergic stimulation.
And lastly, evaluate for the desired therapeutic effect of increased muscle strength, decreased fatigue, and improvement in their ability to perform activities of daily living.
Alright, as a quick recap… Myasthenia gravis is an autoimmune disorder that is caused by destruction of acetylcholine receptors at the neuromuscular junction, leading to fatigue and muscle weakness.

Review5:08–6:08

To help relieve these symptoms, clients with myasthenia gravis can be prescribed acetylcholinesterase inhibitors, which are medications that make more acetylcholine available at the neuromuscular junction.
Potential side effects include cholinergic side effects, such as miosis, blurred vision, headaches, dizziness, and drowsiness; as well as effects in the respiratory, cardiac, and gastrointestinal systems; and excessive cholinergic stimulation, which can lead to a cholinergic crisis.
When caring for a client prescribed an acetylcholinesterase inhibitor, nursing considerations include performing a baseline assessment, as well as monitoring for side effects and the desired therapeutic effects.
Client teaching is focused on safe self-administration, as well as learning to recognize side effects, and when to notify the healthcare provider.
Acetylcholinesterase inhibitors for myasthenia gravis: Video | Osmosis