What is Myasthenia gravis?
Myasthenia gravis (MG) is a chronic autoimmune disorder that affects the neuromuscular junction, causing muscle weakness and fatigue. It is caused by an abnormal immune response that leads to the production of antibodies that attack the acetylcholine receptors on the surface of muscle cells. Acetylcholine is a neurotransmitter that is responsible for transmitting signals from nerves to muscles, so when these receptors are attacked, the communication between nerves and muscles is disrupted.
The symptoms of myasthenia gravis usually include muscle weakness and fatigue, which can affect any voluntary muscle in the body. Common symptoms include drooping eyelids, difficulty chewing or swallowing, slurred speech, and weakness in the arms and legs. The severity of the symptoms can vary from mild to severe and can fluctuate throughout the day.
Myasthenia gravis is a relatively rare condition, with an estimated prevalence of 14-20 cases per 100,000 people worldwide. It can occur at any age but is most commonly diagnosed in women under the age of 40 and men over the age of 60. It is more common in certain ethnic groups, including those of African and Asian descent, and in people with other autoimmune disorders. While myasthenia gravis can affect people of any age, it is most commonly diagnosed in people between the ages of 20 and 50.
How Myasthenia Gravis Affects the Way Medications Work
The way medications work can be affected by myasthenia gravis because the condition can impact the transmission of nerve impulses to the muscles. This can result in a reduced response to medications that act on the nervous system.
For example, drugs that act by blocking acetylcholinesterase, an enzyme that breaks down acetylcholine, the neurotransmitter that carries nerve impulses to the muscles, may have limited effectiveness in MG. This is because the muscles may not respond to the increased amount of acetylcholine that results from the drug.
Similarly, some medications that act on the immune system, may be prescribed to manage MG, but their effectiveness may be impacted by the underlying condition. In addition, medications that have sedative or muscle-relaxant effects should be used with caution in people with MG, as they may exacerbate muscle weakness and fatigue.
List of Drugs To Avoid In Myasthenia Gravis
There are several medications that should be avoided or used with caution in people with m myasthenia gravis they include:
1. Antibiotics: Aminoglycosides such as gentamicin, neomycin, and streptomycin should be avoided in MG because they can worsen muscle weakness and can lead to respiratory failure.
2. Beta-Blockers: Non-selective beta-blockers such as propranolol and timolol should be avoided in MG because they can worsen muscle weakness, especially in the respiratory muscles.
3. Calcium channel blockers: Dihydropyridine calcium channel blockers, such as nifedipine and verapamil, may cause muscle weakness in people with MG.
4. Muscle Relaxants: Depolarizing muscle relaxants such as succinylcholine should be avoided in MG because they can cause prolonged muscle weakness or even respiratory failure.
5. Statins: Statins such as atorvastatin, simvastatin, and lovastatin can cause muscle pain, weakness, and tenderness, which can worsen symptoms of MG.
6. Quinolone antibiotics: Fluoroquinolone antibiotics such as ciprofloxacin and levofloxacin can cause muscle weakness, and in rare cases, can cause muscle rupture in people with MG.
7. Chloroquine and Hydroxychloroquine: These drugs can cause muscle weakness and exacerbate symptoms of MG.
8. Lithium: Lithium can cause neuromuscular side effects such as tremors, muscle weakness, and ataxia, which can worsen MG symptoms.
9. Magnesium salts: Magnesium can cause muscle weakness, which can worsen MG symptoms.
10. Botulinum toxin: Botulinum toxin injections used for cosmetic or medical purposes should be used with caution in people with MG as it can cause muscle weakness.
11. Phenothiazines: Phenothiazines such as chlorpromazine and prochlorperazine can cause muscle weakness, especially in high doses.
12. Phenobarbital: Phenobarbital can cause respiratory depression, which can worsen MG symptoms.
13. Procainamide: Procainamide can cause neuromuscular side effects such as muscle weakness, ataxia, and tremors, which can worsen MG symptoms.
14. Carbamazepine: Carbamazepine can cause neuromuscular side effects such as muscle weakness, ataxia, and tremors, which can worsen MG symptoms.
15. Diphenhydramine: Diphenhydramine can cause muscle weakness, especially in high doses.
16. Gabapentin: Gabapentin can cause neuromuscular side effects such as ataxia, tremors, and muscle weakness, which can worsen MG symptoms.
17. Interferons: Interferons used to treat multiple sclerosis and hepatitis can cause muscle weakness, which can worsen MG symptoms.
18. Methotrexate: Methotrexate can cause neuromuscular side effects such as ataxia, tremors, and muscle weakness, which can worsen MG symptoms.
19. Opioids: Opioids such as morphine and fentanyl can cause respiratory depression, which can worsen MG symptoms.
20. Tacrolimus: Tacrolimus can cause neuromuscular side effects such as tremors, muscle weakness, and ataxia, which can worsen MG symptoms.
It is important to note that this is not an exhaustive list and that people with MG should always consult their healthcare provider before taking any new medication or supplement. The dosage and timing of medication administration may also need to be adjusted based on individual symptoms and response to treatment.
In addition, some medications may be used to treat MG, but their use should be carefully monitored. For example, pyridostigmine, an acetylcholinesterase inhibitor, is commonly used to improve muscle strength in MG, but its use should be closely monitored as it can cause gastrointestinal side effects and cholinergic crisis (excessive stimulation of the nervous system).
Overall, people with MG should work closely with their healthcare provider to develop a comprehensive treatment plan that considers their individual symptoms, medical history, and medication use to manage their condition safely and effectively.
