|Bioavailability||80 to 100%|
|Metabolism||Hepatic partially CYP450:CYP2D6/3A4 substrate|
|Biological half-life||7 hours|
|Excretion||Renal (95%, of which 32% unchanged), fecal (5%)|
|Chemical and physical data|
|Molar mass||287.354 g/mol|
|3D model (Jmol)|
|Melting point||126.5 °C (259.7 °F)|
Galantamine (Nivalin, Razadyne, Razadyne ER, Reminyl, Lycoremine) is used for the treatment of mild to moderate Alzheimer's disease and various other memory impairments, in particular those of vascular origin. It is an alkaloid that is obtained synthetically or from the bulbs and flowers of Galanthus caucasicus (Caucasian snowdrop, Voronov's snowdrop), Galanthus woronowii (Amaryllidaceae) and related genera like Narcissus (daffodil), Leucojum aestivum (snowflake), and Lycoris including Lycoris radiata (red spider lily).
Studies of usage in modern medicine began in the Soviet Union in the 1950s. The active ingredient was extracted, identified, and studied, in particular in relation to its acetylcholinesterase (AChE)-inhibiting properties. The bulk of the work was carried out by Soviet pharmacologists M. D. Mashkovsky and R. P. Kruglikova–Lvova, beginning in 1951. The work of Mashkovsky and Kruglikova-Lvova was the first published work that demonstrated the AChE-inhibiting properties of galantamine.
The first industrial process was developed in Bulgaria by prof. Paskov in 1959 (Nivalin, Sopharma) from a species traditionally used as a popular medicine in Eastern Europe, and, thus, the idea for developing a medicine from these species seems to be based on the local use (i.e., an ethnobotany-driven drug discovery).
Galantamine has been used for decades in Eastern Europe and Russia for various indications such as treatment of myasthenia, myopathy, and sensory and motor dysfunction associated with disorders of the central nervous system. In the US, it is approved by the Food and Drug Administration for the treatment of Alzheimer's disease.
It is available in both a prescription form and as an over the counter supplement.
Research supported in part by the US Army has led to a US patent application for the use of galantamine and/or its derivatives for treatment of organophosphate poisoning. The indications for use of galantamine in the patent application include poisoning by nerve agents "including but not limited to soman, sarin, and VX, tabun, and Novichok agents". Galantamine was studied in the research cited in the patent application for use along with the well-recognized nerve agent antidote atropine. According to the investigators, an unexpected synergistic interaction occurred between galantamine and atropine in an amount of 6 mg/kg or higher. Increasing the dose of galantamine from 5 to 8 mg/kg decreased the dose of atropine needed to protect experimental animals from the toxicity of soman in dosages 1.5.times the dose generally required to kill half the experimental animals.
|treatment of dementia caused by Alzheimer's disease|
|Who might take|
|adults who have mid-to-moderate Alzheimer's disease as indicated by the Mini–mental state examination|
The product is supplied in both a prescription form as well as an over the counter supplement. in twice-a-day tablets, in once-a-day extended-release capsules, and in oral solution.
Galantamine's side effect profile was very similar to that of other cholinesterase inhibitors, with gastrointestinal symptoms being the most notable and most commonly observed. In practice, some other cholinesterase inhibitors might be better tolerated; however, a careful and gradual titration over more than three months may lead to equivalent long-term tolerability.
The U.S. Food and Drug Administration (FDA) and international health authorities have published an alert of galantamine based on data from two studies during the treatment for mild cognitive impairment (MCI); higher mortality rates were seen in drug-treated patients. On April 27, 2006, FDA approved labeling changes concerning all form of galantamine preparations (liquid, regular tablets, and extended release tablets) warning of the risk of bradycardia (slow resting heart rate), and sometimes atrioventricular block, especially in predisposed persons. At the same time, the risk of syncope (fainting) seems to be increased relative to placebo. "In randomized controlled trials, bradycardia was reported more frequently in galantamine-treated patients than in placebo-treated patients, but was rarely severe and rarely led to treatment discontinuation" These side effects have not been reported in Alzheimer's Disease related studies.
Galantamine is a potent allosteric potentiating ligand of human nicotinic acetylcholine receptors (nAChRs) α4β2, α7/5-HT3, α3β4, and α6β4 in certain areas of the brain, as well as a weak competitive and reversible cholinesterase inhibitor in all areas of the body. It increases the concentration and thereby action of acetylcholine in certain parts of the brain. It has shown activity in modulating the nicotinic cholinergic receptors on cholinergic neurons to increase acetylcholine release. It is hypothesized that this action might relieve some of the symptoms of Alzheimer's.
Galantamine in its pure form is a white powder. The atomic resolution 3D structure of the complex of galantamine and its target, acetylcholinesterase, was determined by X-ray crystallography in 1999 (PDB code: 1DX6; see complex). There is no evidence that galantamine alters the course of the underlying dementing process.
Absorption of galantamine is rapid and complete and shows linear pharmacokinetics. It is well absorbed with absolute oral bioavailability between 80 and 100%. It has a half-life of seven hours. Peak effect of inhibiting acetylcholinesterase was achieved about one hour after a single oral dose of 8 mg in some healthy volunteers.
Plasma protein binding of galantamine is about 18%, which is relatively low.
For Razadyne ER, the once-a-day formulation, CYP2D6 poor metabolizers had drug exposures that were approximately 50% higher than for extensive metabolizers. About 7% of the population has this genetic mutation; however, because the drug is individually titrated to tolerability, no specific dosage adjustment is necessary for this population.
Galantamine is produced from natural resources and a patented total synthesis process. Many other synthetic methods exist but have not been implemented on an industrial scale.
- NNFCC Project Factsheet: Sustainable Production of the Natural Product Galanthamine (Defra), NF0612
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- Galantamine Benefits Both Alzheimer's Disease and Vascular Dementia
- Galantamine Improves Attention in Alzheimer's
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- "FDA ALERT: Galantamine hydrobromide (marketed as Razadyne, formerly Reminyl) - Healthcare Professional Sheet" (PDF). Postmarket Drug Safety Information for Patients and Providers. Food and Drug Administration. May 2005. Retrieved 2010-04-02.
- "Safety Alerts for Human Medical Products > Reminyl (galantamine hydrobromide)". # MedWatch The FDA Safety Information and Adverse Event Reporting Program. Food and Drug Administration. March 2005. Retrieved 2010-08-04.
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- "Safety information from Investigational Studies with REMINYL (galantamine hydrobromide) in Mild Cognitive Impairment". Janssen-Ortho Inc. 2005-04-22. Retrieved 29 August 2012.
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- Ortho-McNeil Neurologics, "Razadyne ER US Product Insert", May 2006
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