General Description
A competitive and reversible inhibitor of acetylcholinesterase. Antimyasthenic agent. Can partially reverse the effects of scopolamine-induced amnesia in rats. Reported to improve learning and short-term memory in animal models.
Biological Activity
Galantamine Hydrobromide (GH) is a plant phenanthridine alkaloid which is a selective and reversible acetylcholinesterase (AChE) inhibitor found in several members of the Amaryllidaceae family, such as snowdrops. GH has been approved for symptomatic treatment of AD and vascular dementia by oral or injectable administration. GH concentration-dependent inhibition of AChE activity has antioxidative properties, involving decreased superoxide anion and NO overproduction and restoring mitochondrial membrane potential. GH also possesses memory-enhancing effects via its action as a cholinesterase inhibitor, where it modulates muscarinic transmission, and it is also an allosteric potentiating ligand (APL) of nicotinic acetylcholine receptors (nAChRs). Recently, it was reported that GH potently inhibited delayed rectifier potassium currents, β-amyloid aggregation, and cytotoxicity. These properties contribute to its effectiveness in AD therapy. However, the pharmacological properties of GH administered orally or by injection would likely cause some side effects on the gastrointestinal tract and impact other tissues, organs, and systems outside the central nervous system (CNS) in AD treatment[1].
Biochem/physiol Actions
Primary TargetAcetylcholinesterase
Clinical Use
Galantamine, which was introduced in 2001, is an alkaloid found in plants of the family Amaryllidaceae, which includes the daffodil (Narcissus
pseudonarcissus) and snowflake (Leucojum aestivum). It is a reversible inhibitor of AChE, but it does not appear to inhibit butyrylcholinesterase.
Because it is a tertiary amine and can cross the blood-brain barrier, it is indicated for treatment of mild-to-moderate AD and dementia. It has
been used outside the U.S. for more than 30 years as an anticurare agent in anesthesia. Galantamine differs from other cholinesterase
inhibitors, because it allosterically binds to nicotinic receptors, giving it a dual cholinergic action.
Metabolism
It is metabolized (75%) by CYP2D6 and
CYP3A4 to afford the normethyl, O-desmethyl, and O-desmethylnormethyl metabolites, along with some other minor metabolites. Unlike tacrine,
galantamine is not associated with hepatotoxicity. Its elimination half-life is 5.7 hours.
References
[1] Weize Li . “Pharmacokinetic behavior and efficiency of acetylcholinesterase inhibition in rat brain after intranasal administration of galanthamine hydrobromide loaded flexible liposomes.” Environmental toxicology and pharmacology 34 2 (2012): Pages 272-279.
