ANTIMYASTHENICS (Systemic)
Some commonly used brand names are:
In the U.S.?
- Mestinon 3
- Mestinon Timespans 3
- Mytelase Caplets 1
- Prostigmin 2
- Regonol 3
In Canada?
- Mestinon 3
- Mestinon-SR 3
- Prostigmin 2
- Regonol 3
Note: | For quick reference, the following antimyasthenics are numbered tomatch the corresponding brand names. |
Category
- Antidote, to nondepolarizing neuromuscular block?Neostigmine; Pyridostigmine
- Antimyasthenic?Ambenonium; Neostigmine; Pyridostigmine
- Cholinergic, cholinesterase inhibitor?Ambenonium; Neostigmine; Pyridostigmine
- Diagnostic aid, myasthenia gravis?Neostigmine
Description
Antimyasthenics are given by mouth or by injection to treat myastheniagravis. Neostigmine may also be given by injection as a test for myastheniagravis. Sometimes neostigmine is given by injection to prevent or treat certainurinary tract or intestinal disorders. In addition, neostigmine or pyridostigminemay be given by injection as an antidote to certain types of muscle relaxantsused in surgery.
These medicines are available only with your doctor's prescription in thefollowing dosage forms:
Oral- Ambenonium
- Neostigmine
- Tablets (U.S. and Canada)
- Pyridostigmine
- Syrup (U.S.)
- Tablets (U.S. and Canada)
- Extended-release tablets (U.S. and Canada)
Parenteral- Neostigmine
- Injection (U.S. and Canada)
- Pyridostigmine
- Injection (U.S. and Canada)
Before Using This Medicine
In deciding to use a medicine,the risks of taking the medicine must be weighed against the good it willdo. This is a decision you and your doctor will make. For the antimyasthenics,the following should be considered:
Allergies?Tell your doctor if you have ever had any unusual orallergic reaction to ambenonium, bromides, neostigmine, or pyridostigmine.Also tell your health care professional if you are allergic to any other substances,such as foods, preservatives, or dyes.
Pregnancy?Antimyasthenics have not been reported to cause birthdefects; however, muscle weakness has occurred temporarily in some newbornbabies whose mothers took antimyasthenics during pregnancy.
Breast-feeding?Antimyasthenics have not been reported to causeproblems in nursing babies.
Children?Although there is no specific information comparinguse of antimyasthenics in children with use in other age groups, these medicinesare not expected to cause different side effects or problems in children thanthey do in adults.
Older adults?Many medicines have not been studied specificallyin older people. Therefore, it may not be known whether they work exactlythe same way they do in younger adults. Although there is not much informationcomparing use of antimyasthenics in the elderly with use in other age groups,these medicines are not expected to cause different side effects or problemsin older people than they do in younger adults.
Other medicines?Although certain medicines should not be usedtogether at all, in other cases 2 different medicines may be used togethereven if an interaction might occur. In these cases, your doctor may want tochange the dose, or other precautions may be necessary. When you are takingan antimyasthenic, it is especially important that your health care professionalknows if you are using any of the following:
- Demecarium (e.g., Humorsol) or
- Echothiophate (e.g., Phospholine Iodide) or
- Isoflurophate (e.g., Floropryl) or
- Malathion (e.g., Prioderm)?Using these medicines with antimyasthenicsmay result in serious side effects
- Guanadrel (e.g., Hylorel) or
- Guanethidine (e.g., Ismelin) or
- Mecamylamine (e.g., Inversine) or
- Procainamide (e.g., Pronestyl) or
- Trimethaphan (e.g., Arfonad)?The effects of these medicinesmay interfere with the actions of the antimyasthenics
Other medical problems?The presence of other medicalproblems may affect the use of the antimyasthenics. Make sure you tell yourdoctor if you have any other medical problems, especially:
- Intestinal blockage or
- Urinary tract blockage or
- Urinary tract infection?These medicines may make the conditionworse
Proper Use of This Medicine
Your doctormay want you to take this medicine with food or milk to help lessen the chanceof side effects. If you have any questions about how you should be takingthis medicine, check with your doctor.
Take this medicine only as directed. Do nottake more of it, do not take it more often, and do not take it for a longertime than your doctor ordered. To do so may increase the chance of side effects.
If you are taking this medicine for myasthenia gravis:
- When you first begin taking this medicine, your doctor may want youto keep a daily record of:
- the time you take each dose.
- how long you feel better after taking each dose.
- how long you feel worse.
- any side effects that occur.
This is to help your doctor decide whether the dose of this medicine shouldbe increased or decreased and how often the medicine should be taken in orderfor it to be most effective in your condition.
Dosing?The dose of these medicines will be differentfor different patients. Follow your doctor's orders orthe directions on the label. The following information includes onlythe average doses of these medicines. If your dose isdifferent, do not change it unless your doctor tells you to do so.
The number of tablets or teaspoonfuls of syrup that you take depends onthe strength of the medicine. Also, the number of dosesyou take each day, the time allowed between doses, and the length of timeyou take the medicine depend on the medical problem for which you are takingthese medicines.
For ambenonium- For oral dosage form (tablets):
- For myasthenia gravis:
- Adults and teenagers?At first, the dose is 5 milligrams (mg)three or four times per day. Then, if needed, the dose will be adjusted byyour doctor.
- Children?The dose is based on body weight or size and mustbe determined by your doctor. The total daily dose is usually 300 micrograms(mcg) per kilogram (kg) (136 mcg per pound) of body weight or 10 mg per squaremeter of body surface area. This dose may be divided into three or four smallerdoses. If needed, the total daily dose will be increased to 1.5 mg per kg(0.68 mg per pound) of body weight or 50 mg per square meter of body surfacearea. This dose may be divided into three or four smaller doses.
For neostigmine- For oral dosage form (tablets):
- For myasthenia gravis:
- Adults and teenagers?At first, the dose is 15 milligrams (mg)every three or four hours. Then, the dose is 150 mg taken over a twenty-four-hourperiod.
- Children?The dose is based on body weight or size and mustbe determined by your doctor. The total daily dose is usually 2 mg per kilogram(kg) (0.91 mg per pound) of body weight or 60 mg per square meter of bodysurface area. This dose may be divided into six to eight smaller doses.
- For injection dosage form:
- For myasthenia gravis:
- Adults and teenagers?The usual dose is 500 micrograms (mcg)injected into a muscle or under the skin.
- Children?The dose is based on body weight and must be determinedby your doctor. It is usually 10 to 40 mcg per kg (4.5 to 18.2 mcg per pound)of body weight, injected into a muscle or under the skin, every two or threehours.
- For urinary tract or intestinal disorders:
- Adults and teenagers?The usual dose is 250 to 500 mcg, injectedinto a muscle or under the skin, as needed.
- Children?Use and dose must be determined by your doctor.
For pyridostigmine- For oral dosage forms (syrup and tablets):
- For myasthenia gravis:
- Adults and teenagers?At first, the dose is 30 to 60 milligrams(mg) every three or four hours. Then, the dose is 60 mg to 1.5 grams (usually600 mg) per day.
- Children?The dose is based on body weight or size and mustbe determined by your doctor. The total daily dose is usually 7 mg per kilogram(kg) (3.2 mg per pound) of body weight or 200 mg per square meter of bodysurface area. This dose may be divided into five or six smaller doses.
- For long-acting oral dosage form (extended-releasetablets):
- For myasthenia gravis:
- Adults and teenagers?The usual dose is 180 to 540 mg one ortwo times per day.
- Children?Dose must be determined by your doctor.
- For injection dosage form:
- For myasthenia gravis:
- Adults and teenagers?The usual dose is 2 mg, injected intoa muscle or vein, every two or three hours.
- Children?The dose is based on body weight and must be determinedby your doctor. It is usually 50 to 150 micrograms (mcg) per kg (22.7 to 68.1mcg per pound) of body weight, injected into a muscle every four to six hours.
Missed dose?If you miss a dose of this medicine, take it assoon as you remember. However, if it is almost time for your next dose, skipthe missed dose and go back to your regular dosing schedule. Do not doubledoses.
Storage?To store this medicine:
- Keep out of the reach of children.
- Store away from heat and direct light.
- Do not store the tablet form of this medicine in the bathroom, nearthe kitchen sink, or in other damp places. Heat or moisture may cause themedicine to break down.
- Keep the syrup form of pyridostigmine from freezing.
- Do not keep outdated medicine or medicine no longer needed. Be surethat any discarded medicine is out of the reach of children.
Side Effects of This Medicine
Alongwith its needed effects, a medicine may cause some unwanted effects. Althoughnot all of these side effects may occur, if they do occur they may need medicalattention.
Check with your doctorimmediately if any of the following side effects occur:
Symptoms of overdose
Blurred vision; clumsiness or unsteadiness; confusion; convulsions(seizures); diarrhea (severe); increase in bronchial secretions or watering of mouth (excessive); increasing muscle weakness (especially in the arms, neck, shoulders,and tongue); muscle cramps or twitching; nausea or vomiting (severe); shortnessof breath, troubled breathing, wheezing, or tightness in chest; slow heartbeat; slurred speech; stomach cramps or pain (severe); unusualirritability, nervousness, restlessness, or fear; unusual tiredness or weakness
Also, check with your doctor as soon as possibleif any of the following side effects occur:
Other side effects may occur that usually do not need medical attention.These side effects may go away during treatment as your body adjusts to themedicine. However, check with your doctor if any of the following side effectscontinue or are bothersome:
Other side effects not listed above may also occur in some patients. Ifyou notice any other effects, check with your doctor.
Revised: 07/18/1994
