Myasthenia Gravis

1. Myasthenia Gravis
Management

2. The drugs used in treatment of Myasthenia Gravis :
1.Acetylcholinesterase inhibitors:
a.Neostigmine
b.Pyridostigmine
c.Edrophonium
2.Immunosuppressive drugs
a.Corticosteroids
b.Azathioprine
3.Others
Dihydropyridines

3. • Cholinesterase inhibitors prevent the
breakdown of acetylcholine by
cholinesterase, and the concentration
of acetylcholine at the NMJ
increases,overcoming the effect of
inhibiting antibody.
• Corticosteroids such as
prednisolone , presumably act by
suppressing lymphocytes production
of acetylcholine receptor antibody
Mechanism of action of drugs used
in treatment of myasthenia gravis

4. • Plasmapheresis is sometimes used in
myasthenia Gravis to remove
antibodies from circulation
thus,reduces degree of block
• Plasma exchange can give a short
term relief in some cases.

5. The use of drugs in Myasthenia
Gravis

6. 1.In diagnosis
• Edrophonium :
• Is a cholinesterase inhibitor with very short duration of action.
• Can also be used in the differentiation of a myasthenia crisis (due to severe
disease or too little cholinterase inhibition) from a cholinergic crisis (due to too
much cholinesterse inhibition and excess acetylcholine at NMJ)
• In cholinergic crisis very transiently worsen the condition while greatly improve
a myasthenia crisis.
• Here we observe respiratory muscles and patient should be in intensive care.

8. Edrophonium given intravenously
usually the initial dose of 2mg given.
If no response within 30s no
untoward effects occurred , give 3mg
…still on response then give 5mg.
To prevent bradycardia …Atropine
(0.6 to 1.2 mg ) should be given

9. 2. Treatment
• Neostigmine and Pyridostigmine
• Cholinesterase inhibitors are used in mild cases of myasthenia .
• They are similar in their efficacy but some of their distinguishing features are :
• Neostigmine after oral administration acts for 30 to 45 mins which is shorter than
duration of action of pyridostigmine
• Muscarinic adverse effects,particularly abdominal cramps, nausea and diarrhoea
maybe worsen with Neostigmine.
• Some patients find Neostigmine gives quicker and slightly greater improvement in
muscle strength
• Pyridostigmine is more effective in bulbar muscle weakness

10. Treatment is usually
started with
neostigmine 15 mg
orally 6 hourly; dose
and frequency is then
adjusted to obtain
optimum relief from
weakness. However,
the dosage
requirement may
fluctuate from time to
time and there are
often unpredictable
periods of remission
and excerbation.
Pyridostigmine is usually
preferred to Neostigmine.
Dosage of 30-60mg 6 to 8
hourly is started.
Dosage can be increased
by reducing the interval
between the dosage
Edrophonium can be
used to test adequacy
of therapy with
cholinesterase
inhibitors . 2mg
intravenously given
about 1 hr after oral
administration
cholinesterase
inhibitors. When it’s
action is at peak patient
strength is tested
before and after. If
strength improves the
dose may be increased.
This should be done
when patient is in
intensive care ideally.

12. Unacceptable muscarinic adverse
effects can be controlled by giving
an antimuscarinic cholinoceptor
anatagonist, such as atropine
(0.6mg daily orally)

13. Thymectomy is
done in
myasthenia
Gravis patients
usually
considered in
young adults

14. Corticosteroids and Azathioprine
• In patients where myasthenia Gravis is limited to ocular muscles.prednisolone
can be given initially to replace the cholinesterase inhibitors if they are
ineffective.
• Prednisolone low dose - 10mg orally alternate days. This can be gradually
increased in increaments of 5mg once a week to total 1.5mg/kg on alternate
days
• If large doses of steroids given too quickly it can worsen myasthenia so patient
should be admitted for steroid therapy.
• In severe cases of Mysthenia where thymectomy also didn’t respond , the
combination of prednisolone with Azathioprine (2.5mg/kg) can be effective.