Drugs that worsen MG Flashcards
What are the 2 general mechanisms by which a drug can cause MG or MG-like symptoms?
- Eliciting an autoimmune reaction against the neuromuscular junction.
- Interfering with neuromuscular transmission.
- 1 and 2
Average time from ICI initiation to MG symptoms onset
4 weeks, ranging from 1 week to 4 months
AChR Ab seropositivity in ICI-associated MG patients
Present in about two-thirds of patients
What percentage of patients with ICI-related MG experience respiratory failure?
45%
What is the fatality rate for patients with ICI-related MG?
25-40%
What percentage of ICI-induced MG cases overlap with myositis?
40% of ICI-induced MG cases overlap with myositis.
What is the prognosis for overlapping cases of ICI-induced MG and myositis?
Overlapping cases have a worse prognosis.
What is a rare but potentially fatal complication of ICI treatment?
Overlap syndrome of MG, myositis, and myocarditis.
What is recommended for MG patients treated with ICIs?
MG patients should be on maintenance steroid treatment.
What is recommended as the first line of treatment for MG patients treated with ICIs (beyond steroids)?
Use of PLEX or IVIG treatment improves the outcome.
What percentage of patients taking D-penicillamine develop MG?
1-7%
When do MG symptoms typically manifest after starting D-penicillamine?
MG symptoms manifest 6-7 months (but can be several years) after starting D-penicillamine.
What percentage of MG cases go into complete remission after stopping D-penicillamine?
70% of MG cases go into complete remission after discontinuing D-penicillamine.
What are the potential causes of MG by Tyrosine Kinase Inhibitors?
Immune dysregulation or direct effect on neuromuscular transmission.
Is there a clear contraindication to using Tyrosine Kinase Inhibitors due to MG emergence?
No, emergence of MG is rarely reported, so no clear contraindication exists.
What treatment in Hepatitis C patients can cause de novo myasthenia gravis or exacerbate myasthenia gravis?
IFN alpha
What do authors suggest regarding macrolide use in MG patients?
Avoid macrolides if there is another alternative.
Why should fluoroquinolones be avoided in MG patients?
They directly affect the AChR ion channel.
Aminoglycosides effect on MG patients
Cause MG exacerbation and myasthenia-like symptoms in critically ill non-MG patients. Examples include Neomycin, Amikacin, streptomycin, gentamicin.
Which aminoglycoside does not cause neuromuscular blockade at effective antibacterial concentrations?
Tobramycin
Which class of antibiotics is recommended as first-line for MG patients?
Penicillins are recommended as first-line antibiotics for MG patients.
Which drugs can be safely administered to MG patients?
Cephalosporins, sulfa drugs (eg TMP/SMX), clindamycin, tetracyclines, polymyxin B, nitrofurantoin.
What effect can ß-adrenergic and calcium channel blockers have on MG symptoms?
They may cause transient exacerbation of MG symptoms.
Who can generally undergo treatment with ß adrenergic or calcium channel blockers?
MG patients in remission or well controlled.
How does Chloroquine cause MG?
Emergence of myasthenia through AChR antibodies
Which drug similar to chloroquine has been reported to onset and exacerbate MG?
Hydroxychloroquine
What symptoms has procainamide caused in nonmyasthenic patients with kidney failure?
MG-like symptoms
What effect does propafenone have on MG symptoms?
Causes worsening of MG symptoms within hours.
Which class of antiarrhythmics has no reports of worsening MG symptoms?
Class Ib antiarrhythmics such as flecainide and amiodarone.
What condition may statins exacerbate or induce?
Statins may cause MG-like symptoms, MG exacerbation, and induction of de novo MG.
Why should magnesium supplementation be used cautiously in MG patients?
It can exacerbate symptoms in myasthenia gravis patients.
What is the mechanism of action for depolarizing neuromuscular blockers (NMBs)?
Depolarizing NMBs bind to AChR, causing activation and subsequent muscle relaxation as the AchR becomes insensitive to Ach.
What is the only depolarizing neuromuscular blocker available in the US market?
Succinylcholine
True/False:
AchEI can reverse succinylcholine
False. In fact succinylcholine effects can be enhanced by AchEI
Is succinylcholine absolutely contraindicated in MG?
No, it is not absolutely contraindicated in MG.
How do MG patients respond to nondepolarizing neuromuscular blockers?
MG patients have prolonged and unpredictable block from nondepolarizing neuromuscular blockers (eg vecuronium, rocuronium, mivacurium) so use lower doses.
Which inhaled anesthetics may cause neuromuscular block in MG patients similar to non depolarizing NMBs?
Halothane, isoflurane, enflurane, and sevoflurane.
What is Sugammadex?
A y-cyclodextrin that encapsulates and reduces the activity of NMBs.
What is a key advantage of sugammadex over acetylcholinesterase inhibitors?
Lack of increase in ACh at the neuromuscular junction, reducing postoperative complications.
Which was the first typical antipsychotic associated with MG exacerbation?
Chlorpromazine
Which antipsychotics are reported to worsen symptoms in MG patients?
Pimozide, thioridazine, clozapine, olanzapine, haloperidol, quetiapine, risperidone, olanzapine.
Which atypical antipsychotics affect neuromuscular transmission?
Clozapine, olanzapine, sulpiride, risperidone
What happens to myasthenic symptoms after starting lithium?
They emerge shortly after starting lithium.
What is the conclusion about antiepileptics in MG patients?
Antiepileptics are generally safe in MG patients due to rarity of interaction reports.
In which MG subtype may pyridostigmine be ineffective or worsen symptoms?
MuSK positive myasthenia gravis (MG).
What is the recommendation for botulinum toxin A treatment in MG patients?
It should preferably be avoided in MG patients.
