ambenonium

Ambenonium is a medication used in the treatment of myasthenia gravis, an autoimmune neuromuscular disease. Myasthenia gravis affects motor nerve function causing weakness in the skeletal muscles, which results in weakness of arms and legs, and difficulties with eye and eyelid movement, talking, chewing, swallowing, facial expressions and breathing. Ambenonium improves the symptoms of myasthenia gravis by enhancing the transmission of nerve signals to the muscles.

Acetylcholine is a natural chemical (neurotransmitter) that nerve endings in muscles secrete to stimulate muscle contraction. Acetylcholine stimulates protein molecules known as cholinergic receptors in the neuromuscular junctions making the muscle fibers contract. There are two types of cholinergic receptors, muscarinic and nicotinic, with diverse functions in the body. In patients with myasthenia gravis, autoimmune antibodies form against these receptors and damage and destroy them, preventing normal neurotransmission.

Ambenonium improves nerve signaling to the muscle fibers by preventing the breakdown of acetylcholine and enhancing its bioavailability. Neurotransmitters are normally broken down and reabsorbed by the nerve cells after the completion of neurotransmission, as part of a natural process. Acetylcholine is broken down by the enzyme cholinesterase. Ambenonium blocks the activity of cholinesterase and prolongs the activity of acetylcholine.

Ambenonium was discontinued by the manufacturer on June 25, 2012 and is no longer available in the U.S.

• Do not use ambenonium in patients with hypersensitivity to any component of the formulation.
• Do not administer routinely with atropine, because it may suppress the muscarinic symptoms of excessive gastrointestinal stimulation but the more serious symptoms of muscle twitches (fasciculation) and voluntary muscle paralysis may remain.
• Do not administer concurrently with mecamylamine or other ganglionic block agents which reduce the activity of acetylcholine.
• Do not use ambenonium concurrently with other drugs that enhance acetylcholine activity, except under strict medical supervision, because the drug has more prolonged action than other antimyasthenic drugs.
• There is very little warning before overdosage of ambenonium because of a very narrow margin between the first appearance of side effects and serious toxic effects. Administer the drug with extreme care and supervision, particularly when increasing dosage.
• Use ambenonium with caution in patients with:
  • Asthma
  • Parkinson’s disease
  • Mechanical intestinal or urinary obstruction

Common side effects of ambenonium include:

• Nausea
• Vomiting
• Abdominal cramps
• Diarrhea
• Excessive salivation
• Increase in bronchial secretions
• Excessive watering of eyes (lachrymation)
• Sweating
• Excessive urination (pollakiuria)
• Urinary urgency
• Muscle twitches (fasciculation)
• Paralysis of tongue muscles
• Paralysis of respiratory muscles
• Difficulty swallowing
• Difficulty breathing
• Shortness of breath (dyspnea)
• Increase in blood pressure
• Slow heart rate (bradycardia)
• Constriction of pupils (miosis)
• Anxiety
• Panic
• General unwell feeling (malaise)
• Vertigo

Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:

• Serious heart symptoms include fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness;
• Severe headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
• Severe nervous system reaction with very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out; or
• Serious eye symptoms include blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

Tablet

• 10 mg

Myasthenia Gravis

Adult:

• Initial: 5 mg orally every 6-8 hours
• Maintenance: 15-100 mg/day, usual 40 mg/day
• Up to 50-75 mg orally every 6-8 hours

Pediatric:

• Initial: 0.3 mg/kg/day divided every 6-8 hours orally
• Maintenance: 1.5 mg/kg/day divided every 6-8 hours orally

Overdose

• Symptoms of ambenonium overdose include increased gastrointestinal stimulation with epigastric distress, abdominal cramps, vomiting, diarrhea and excessive salivation, excessive urination, urinary urgency, cold sweats, constriction of pupils, blurred vision, respiratory and swallowing difficulty, muscle twitches and paralysis of voluntary muscles.
• Overdose treatment includes discontinuation of ambenonium, administration of atropine to reverse acetylcholine effects on the muscarinic receptors and pralidoxime chloride to reverse its effects on the nicotinic receptors. Other supportive treatments such as oxygen and artificial respiration may be used as required.

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

• Ambenonium has no listed severe, serious, moderate, or mild interactions with other drugs.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

• The safety of ambenonium use in pregnant women has not been established. Ambenonium should be used in women who are pregnant or have pregnancy potential only if clearly needed, and if maternal benefits outweigh potential risks to the fetus.
• It is not known if ambenonium is present in breastmilk, but it is likely because many drugs are excreted in breastmilk. Decision to discontinue the drug or nursing should be made depending on the mother’s clinical need, because of the potential for serious adverse reactions in the breastfed infant.

• Take ambenonium exactly as prescribed.
• Store safely out of reach of children.
• In case of overdose, seek immediate medical help or contact Poison Control.