Medications

There are two types of medications used to treat MG. One group—anitcholinesterases—temporarily relieves the symptoms of MG. Another group—immunosuppressants—attacks the disease at its source. By suppressing the body’s immune system, these drugs stop the body from producing defective antibodies in the first place. But these drugs also can have serious side effects.

Doctors may prescribe one or a combination of these medications. It often takes time to determine the best medication and dosage.

Anticholinesterase Medication

This is typically the first type of medication prescribed because it is has the fewest long-term side effects. It also is the most rapid-acting medication available. These drugs prevent the breakdown of acetycholine—the chemical messenger that causes a muscle contraction. More acetycholine generally results in greater muscle strength. Since anticholinesterase medications do not target the immune problem in MG, they do not alter the course of the disease. Thus, they are not a treatment, but are a way of managing MG symptoms temporarily.

The most commonly prescribed medication of this type is pyridostigmine bromide (Mestinon). It’s available in tablet or liquid, and comes in a time-release form.

Acetycholinesterases can cause stomach cramps and diarrhea; it helps to take them with bland food like applesauce or yogurt. Other common side effects include muscle twitching, muscle cramps and sweatiness. Sometimes these symptoms appear when too much medication is taken. If you have these symptoms, you should talk with your doctor to see if you should reduce your dose.

Immunosuppressant Medications

Immunosuppressants stop your body from producing the harmful antibodies that cause MG weakness in the first place.

At the same time, they also reduce the body’s production of good antibodies—which makes you more susceptible to infection and other diseases. While you’re taking immunosuppressants, it’s important to avoid people with contagious diseases. And if you’re quite ill, you may need to avoid crowds and wash your hands often.

• Prednisone significantly relieves MG symptoms for a large majority of myasthenics. This drug is not as fast acting as anticholinesterases, but it is faster than other immunosuppressants, and it is relatively inexpensive. It resembles natural hormones produced by the cortex of the human adrenal gland.
  
  While prednisone can be very effective in treating myasthenia, it carries the risk of serious side effects; their severity depends on the dosage and length of time prednisone is used. These include insomnia, mood changes, weight gain, fluid retention, reduced resistance to infection, increased susceptibility to diabetes, high blood pressure, osteoporosis, glaucoma, cataracts, and stomach ulcers, plus a host of other less common side effects. Most of these side effects can be managed with other medication. It also is very important to “eat healthy” which in this case means eating a well-balanced diet that is high in potassium and calcium and low in sodium, fat and cholesterol. This can help prevent bone thinning, reduce fluid retention and minimize weight gain, for starters.
  
  When you take prednisone, it stops the body’s natural production of adrenal hormones. That’s why most patients get off prednisone over a period of months or even years; the dose must be tapered gradually to “reawaken” the body’s natural hormones.
• Other immunosuppressant medications. There are a number of other medications used to treat MG. Many were developed initially for organ transplant patients, or for treating other immune-related diseases. These include azathioprine (Imuran), mycophenylate mofetil (CellCept), cyclosporine (Sandimmune, Neoral), tacrolimus (Prograf), and cyclophosphamide (Cytoxan, Neosar). If one of these medications helps a particular myasthenic, its use can eliminate the need for prednisone, or allow a lowering of its dose. These medications are complicated to administer. They can take months to become effective; dosage varies from person to person; and each drug has its own side effects and drug interactions. Your doctor should go through the details of these medications with you.

Reviewed by the MGF of Illinois Medical Advisory Board, September 2008.