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​​Safety of antibiotics in Myasthenia Gravis 

Myasthenia gravis (MG) is an autoimmune condition that affects neuromuscular transmission leading to muscle weakness, muscle fatigue and general weakness. This can manifest with unpleasant but benign symptoms such as double vision, but often can lead to the inability to eat or drink, aspiration pneumonia, respiratory failure (myasthenia crisis) or a patient becoming bedridden due to severe weakness of the muscles of the limbs. The condition is normally treated by a combination of drugs that increase the muscle contraction (such as pyridostigmine) or anti-inflammatory treatments (steroids, IV immunoglobulins or immunosuppressants).

The disease can flare up and cause severe symptoms, which can be potentially life-threatening. The most common causes for a sudden deterioration of myasthenia symptoms are infection, not taking/unable to take MG medications and certain medication such as antibiotics.
Some antibiotics can reduce the effectiveness of neuromuscular transmission in a patient with Myasthenia Gravis (MG) and can exacerbate symptoms of the disease. If a patient requires antibiotic treatment for an infection then the appropriate antibiotics should be utilized and discussed with the patient. It is important to be aware of significant adverse effects especially if a patient becomes weaker in the setting of antibiotic use. Any reaction to any drug can be very specific to the individual patient.
 
 The table below provides information about which antibiotics are contraindicated in MG or are to be used with caution. Note: this advice is for ANY antibiotic formulation, including eye-drops, ear-drops, creams and ointments.
(Please note that this is not a comprehensive list. Please seek advice from pharmacy or neurology if any other antibiotics are required or queries with stated antibiotics).
 
 
Contraindicated in myasthenia gravis
 
Aminoglycosides – amikacin, gentamicin, neomycin, streptomycin and tobramycin
Contraindicated in patients with myasthenia gravis – inhibits acetylcholine release from presynaptic neuron; also has some postsynaptic curare-like action. Aggravates muscle weakness. Aminoglycosides have been associated with death when used in patients with a history of myasthenia gravis.
Azithromycin
Exacerbations of the symptoms of myasthenia gravis and new onset of myasthenia gravis have been reported.
Clindamycin
Has been shown to have neuromuscular blocking properties and may enhance the effect of other drugs with this action.
Fluroquinolones – ciprofloxacin, levofloxacin
Fluoroquinolones should be avoided in patients with a history of myasthenia gravis. Neuromuscular blocking activity therefore may exacerbate muscle weakness. Can also unmask subclinical myasthenia gravis.
Macrolides e.g.  erythromycin and clarithromycin
Exacerbation of symptoms of myasthenia gravis and trigger new onset of symptoms of myasthenic syndrome has been reported in patients.
 
 
 
All of these antibiotics have a very high risk of worsening MG and should ONLY be used for the treatment of a serious infection that cannot be treated otherwise on specialist advice. Before starting the medication contact neurology to discuss the patient, the MG treatment may need adjusting and the patient will require strict monitoring.
 
In addition, aminoglycosides are contraindicated by the manufacturers in MG patients so usage should be on specialist advice only.
 
 
Cautioned in myasthenia gravis
Co-trimoxazole
Sulphonamides have a depressant effect on neuromuscular junction and may increase weakness.
Lymecycline
Can cause weak neuromuscular blockade so should be used with caution in myasthenia gravis
Other fluoroquinolones – ofloxacin, moxifloxacin
 
Fluoroquinolones should be avoided in patients with a history of myasthenia gravis. Neuromuscular blocking activity therefore may exacerbate muscle weakness.
Postmarketing serious adverse reactions, including deaths and the requirement for respiratory support have been associated with fluoroquinolone use in patient with myasthenia gravis.
Tigecycline
Due to a potential for weak neuromuscular blockade, care should be taken in administering tetracyclines to patients with myasthenia gravis
Tetracyclines – doxycycline, oxytetracycline, minocycline
Due to a potential weak neuromuscular blockade, care should be taken in administering tetracyclines to patients with myasthenia gravis.
Caution is advised in patients with myasthenia gravis as tetracyclines can cause weak neuromuscular blockade.
Vancomycin
May potentiate the neuromuscular blockade of succinylcholine.
 
Medicines in this group can block neuromuscular transmission to some extent. The treatments are likely to be safe in patients with stable ocular myasthenia or MG patients who are in remission, but may pose a risk for less stable MG patients. Patients should be monitored closely and it is advised to contact neurology if there are concerns.
 
 
 
Considered safe in myasthenia gravis
 
Amoxicillin
No information found to suggest a problem in myasthenia gravis
Benzylpenicillin
No information found to suggest a problem in myasthenia gravis
Ceftriaxone
No information found to suggest a problem in myasthenia gravis
Ceftazidime
No information found to suggest a problem in myasthenia gravis
Co-amoxiclav
No information found to suggest a problem in myasthenia gravis
Daptomycin
No information found to suggest a problem in myasthenia gravis. Muscle weakness may be due to raised creatinine kinase (CK).
Flucloxacillin
No information found to suggest a problem in myasthenia gravis
Fluconazole
No information found to suggest a problem in myasthenia gravis
Linezolid
No information found to suggest a problem in myasthenia gravis
Meropenem
No information found to suggest a problem in myasthenia gravis
Metronidazole
No information found to suggest a problem in myasthenia gravis
Micafungin
No information found to suggest a problem in myasthenia gravis
​Piperacillin & Tazobactam (Tazocin) Neuromuscular blockade produced by muscle relaxants could be prolonged in the presence of piperacillin.
Teicoplanin
No information found to suggest a problem in myasthenia gravis
Temocillin
No information found to suggest a problem in myasthenia gravis
Trimethoprim
No information found to suggest a problem in myasthenia gravis
 
Please note there is a risk for increasing weakness in MG patients with any new medication however these antibiotics have not been linked to exacerbation of MG symptoms. In most cases these antibiotics can be prescribed without the need to take any additional precautions compared with any other patient groups.
 
Other useful links for information on medication in Myasthenia Gravis:
·    Medications and Myasthenia Gravis; http://www.myasthenia.org/LinkClick.aspx?fileticket=JuFvZPPq2vg%3D
 
 
 
 
References:
-         Myaware.org, drugs to avoid in Myasthenia Gravis. https://www.myaware.org/drugs-to-avoid (accessed March 2019)
-      Drugs that may worsen Myasthenia Gravis. https://neurology.uams.edu/wp-content/uploads/sites/49/2018/03/Drugs-that-may-worsen-Myasthenia-Gravis.pdf (Accessed March 2019)
-      Medications and Myasthenia Gravis (A reference for health care professionals) 2007. http://www.myasthenia.org/LinkClick.aspx?fileticket=JuFvZPPq2vg%3D (Accessed March 2019)
-      Summary of Product Characteristics. www.medicines.org.uk (Accessed March 2019)
-      Antibiotics in myasthenia gravis - safeline, Aintree university hospital March 2019.