September 2018 By PsychDB.com

Galantamine

Galantamine (Tradename: Razadyne) is an acetylcholinesterase inhibitor and cognitive-enhancing medication. It is used in the treatment of dementias and neurodegenerative disorders.

Acetylcholinesterase inhibitors, including donepezil, rivastigmine, and galantamine all inhibit acetylcholinesterase. The break down of acetylcholine is prevented by the drug binding and reversibly inactivating cholinesterases. This inhibits the hydrolysis of acetylcholine. As a result, acetylcholine levels increase in the brain, which may optimize function of remaining intact cholinergic neurons. This is thought to improve memory and cognitive function. However, treatment does not alter the underlying course of the disease. The increase in acetylcholine also occurs in other organ systems innervated by cholinergic neurons, and leads to the side effects in this medication class as well.

Acetylcholinesterase inhibitors are indicated in:

  • Starting dose for galantamine immediate-release tablet (or solution) is 4 mg PO BID (should remain on this dose for a minimum of 4 weeks)
  • If well tolerated, can increase to 8 mg PO BID (should remain on this dose for a minimum of 4 weeks)
  • If well tolerated, can increase to 12 mg PO BID (maximum dose)
  • If galantamine is stopped and therapy interrupted for more than several days, the medication should be slowly retitrated

A baseline ECG (to rule out any conduction abnormalities), heart rate, weight, and blood pressure should be obtained prior to starting an acetylcholinesterase inhibitor.

  • Can cause dizziness and drowsiness, especially during initiation of therapy
  • At lower doses, can cause nausea, diarrhea, vomiting, insomnia, fatigue, muscle cramps, loss of appetite, and weight loss, and bradycardia
    • These side effects will usually resolve on its own
    • Discontinue if bradycardia develops or there is a significant conduction abnormality (i.e. - more than a first degree heart block)
  • At higher doses, side effects include headaches, dizziness, drowsiness, blurred vision, urinary frequency and incontinence
  • Can aggravate asthma and other breathing problems
  • Can increase the risk of seizures
  • Make sure to warn patients of possible GI side effects!
  • Anticholinergic drugs (e.g. - atropine, benztropine) may be less effective when combined with an acetylcholinesterase inhibitor. The cholinergic action of acetylcholinesterase inhibitors (an agonist) opposes the anticholinergic action (antagonists) of these medications. Anticholinergic drugs can also decrease the cholinergic action of acetylcholinesterase inhibitor, reducing its efficacy.
  • Beta-blockers (e.g. - propranolol, atenolol, timolol) combined with acetylcholinesterase inhibitors can increase the risk of bradycardia, heart block, and syncope.

Relative

  • Weight loss
    • Lower-weight patients should be closely monitored for vomiting, diarrhea, and loss of appetite. This applies to especially frail, elderly women, who tend to be more frequently affected
  • Upcoming surgeries
    • Acetylcholinesterase inhibitors can interact with muscle-relaxing anesthesias such as succinylcholine
  • Anti-arrhythmic medications
  • History of gastric ulcers or regular NSAID (aspirin, ibuprofen, and naproxen)
    • Should be monitored for signs and symptoms of ulcers and gastrointestinal bleeding
  • Significant alcohol use can induce depressant effects, reduce the efficacy, and intensify the side effects of acetylcholinesterase inhibitors

Absolute

  • Bradycardia (<50bpm) or AV block
  • Severe asthma and COPD, because the increase in acetylcholine activity can cause worsening respiratory function. (Remember that anticholinergics are frequently used as bronchodilators in the management of asthma/COPD!)
  • Severe hepatic or renal failure
  • Obstructive Urinary Disease
  • Seizures