MYASTHENIA 

​

PYRIDOSTIGMINE

30MG QID

MAX 120 MG QID

 

IF ASYMPTOMATIC AFTER INTRODUCTION OF PREDNISOLONE ONLY, WITHDRAW SLOWLY AT 30–60 MG PER WEEK, UNTIL WITHDRAWN, OR USE THE LOWEST EFFECTIVE DOSE

 

 

START PREDNISOLONE 10MG OD

INCREASE BY 5MG EVERY WEEK

TILL 1MG/KG (OCULAR MYASTHENIA 0.75MG/KG)

 

STAY ON THIS DOSE TILL 2-3 MONTHS OR TILL REMISSION (SYMPTOMATIC AND ABLE TO WITHDRAW/ STOP PYRIDOSTIGMINE)

 

TAPERING:

TAPER 10MG EVERY ALTERNATE DAY EVERY MONTH TILL 40MG.

THEN 5 MG ALTERNATE DOSE EVERY MONTH.

 

THE LOWEST EFFECTIVE CORTICOSTEROID DOSE BEFORE RELAPSE IS THE MAINTENANCE DOSE.

 

IF THE RELAPSE OCCURRED ON A DOSE OF PREDNISOLONE ABOVE 15–20 MG ALTERNATE DAYS IN A PATIENT TREATED WITHOUT RECEIVING AZATHIOPRINE, THEN AZATHIOPRINE SHOULD BE INTRODUCED.

 

A PREDNISOLONE DOSE ABOVE 15–20 MG ON ALTERNATE DAYS IS PROBABLY TOO HIGH FOR LONG-TERM USE, AND IS AN INDICATION TO INTRODUCE IMMUNOSUPPRESSION WITH AZATHIOPRINE.

 

CONTINUING A LOW DOSE LONG TERM CAN HELP TO MAINTAIN THE TREATMENT GOAL

 

AN ALTERNATE DAY CORTICOSTEROID REGIMEN PROBABLY REDUCES SIDE EFFECTS. DAILY CORTICOSTEROIDS MAY BE SUITABLE IN SOME PATIENTS, SUCH AS THOSE WITH DIABETES MELLITUS

 

MONITORING

HBA1C EVERY FEW MONTHS

BLOOD PRESSURE

BONE DENSITY MONITORING

EYE EXAM FOR GLAUCOMA AND CATARACTS.

GI ULCERS

 

 

SUPPLEMENT:

CALCIUM 500 MG TID

VIT D 400 IU/ DAY

POST MENOPAUSE: BISPHOSPHONATES

 

AZATHIOPRINE

FINAL DOSE: 2-3 MG/ KG

START 50 MG OD, INCREASE DOSE EVERY 2 WEEKS 

 

INDICATIONS

1. UNABLE TO TOLERATE STEROIDS

2. NO REMISSION ON STEROIDS

3. RELATIVE CONTRAINDICATION FOR STEROIDS: H/O DM, OSTEOPOROSIS OR HTN

 

MONITORING

TPMT GENETIC TEST BEFORE STARTING

TMPT DEFICIENCY IS NOT A CONTRAINDICATION TO USING AZATHIOPRINE BUT MAY REDUCE THE DOSE REQUIRED.

 

IF HETEROZYGOUS OR HOMOZYGOUS:

START ON MYCOPHENOLATE MOEFETIL

 

AZA RISES MCV

REDUCE DOSE IF TLS <4000

STOP IF TLC<3000 or NEUTROPHIL COUNT<2000

RESPONSE:  LYMPHOCYTE COUNT 600-1000, MCV INCREASE BY 5%.

REPEAT LFT AND CBC EVERY 1 MONTHS, INITIALLY ONCE EVERY WEEK FOR 1 MONTH

 

 

METHYLPREDNISOLONE:

INTRAVENOUS HIGH-DOSE CORTICOSTEROID-PULSE THERAPY HAS BEEN USED TO TREAT SEVERE EXACERBATIONS. 500 TO 2000 MG METHYLPREDNISOLONE IS GIVEN IV, FOLLOWED BY ORAL MAINTENANCE THERAPY. PULSE THERAPY MAY BE REPEATED AT INTERVALS OF 5 DAYS.

THIS HIGH-DOSE THERAPY CAN LEAD TO A RAPID, TEMPORARY WORSENING IN PATIENTS WITH BULBAR SYMPTOMS; ACUTE STEROID MYOPATHY HAS ALSO BEEN DESCRIBED.

 

THEREFORE, CORTICOSTEROID-PULSE THERAPY IS RECOMMENDED ONLY IN IMPENDING OR MYASTHENIA CRISIS, TOGETHER WITH PLEX OR IVIG.

 

 

SURGERY:

IF THE SERUM ACH-R ANTIBODY IS POSITIVE AND THE PATIENT IS AGED UNDER 45 YEARS: CONSIDER THYMECTOMY AT PRESENTATION.

 

OFFERING VIDEO-ASSISTED THORACOSCOPIC THYMECTOMY EVEN BEFORE STARTING CORTICOSTEROIDS MAY BE AN OPTION FOR SOME PATIENTS. AS THYMECTOMY PRODUCES BENEFIT SLOWLY, THIS IS APPROPRIATE ONLY FOR PATIENTS WITH MILD DISEASE.

 

THE BENEFIT OF THYMECTOMY IN PATIENTS WITHOUT DETECTABLE ACHR ANTIBODIES IS NOT CLEAR. THE BENEFITS OF THYMECTOMY APPEAR TO BE GREATEST FOR ACHR-ANTIBODY POSITIVE PATIENTS, FOLLOWED BY DOUBLE SERONEGATIVE PATENTS, THEN FOLLOWED BY THOSE WITH MUSK ANTIBODIES.

 

THERE IS INSUFFICIENT EVIDENCE REGARDING THE EFFICACY OF THYMECTOMY IN MUSK-MG PATIENTS,

 

THYMECTOMY IS ALWAYS AN ELECTIVE PROCEDURE, AND THE SURGICAL RISK IS LOW IF PERFORMED WHEN THE DISEASE IS STABLE, USUALLY AFTER EFFECTIVE PRETREATMENT, E.G., WITH PLEX, IVIG OR CORTICOSTEROIDS.

PATIENTS AGED 15-50 YEARS WITH GENERALIZED MG APPEAR TO BENEFIT MOST CLEARLY FROM THYMECTOMY IF IT IS CARRIED OUT WITHIN 1-2 YEARS AFTER DIAGNOSIS.

 

 

RELAPSE

PATIENTS WITH MYASTHENIA DETERIORATION SHOULD RETURN TO THE STEROID INCREASE PROTOCOL, INCREASING PREDNISOLONE UNTIL SYMPTOMS ARE CONTROLLED UP TO THE TARGET DOSE OF 1MG/KG OR 0.75 MG/KG FOR OCULAR MYASTHENIA.

 

IF THE RELAPSE OCCURRED ON A DOSE OF PREDNISOLONE ABOVE 15–20 MG ALTERNATE DAYS IN A PATIENT TREATED WITHOUT RECEIVING AZATHIOPRINE, THEN AZATHIOPRINE SHOULD BE INTRODUCED

 

 

IVIG:

PLEX MAY BE MORE EFFECTIVE THAN IVIG IN MUSK-MG

THE USE OF IVIG AS MAINTENANCE THERAPY CAN BE CONSIDERED FOR PATIENTS WITH REFRACTORY MG OR FOR THOSE IN WHOM IS AGENTS ARE RELATIVELY CONTRAINDICATED.

 

 

MUSK:

PATIENTS WITH MUSK-MG MAY NOT RESPOND OR BECOME WORSE WITH CHOLINESTERASE INHIBITORS, EVEN AT LOW DOSES, AND REQUIRE SPECIAL MEDICAL ATTENTION

​