Galantamine is a type of acetylcholinesterase inhibitor. It is an alkaloid extracted from the bulbs and flowers of Galanthus nivalis (common snowdrop), Galanthus caucasicus (Caucasian snowdrop), Galanthus woronowii (Voronov's snowdrop), and other members of the family Amaryllidaceae, such as Narcissus (daffodil), Leucojum aestivum (snowflake), and Lycoris including Lycoris radiata (red spider lily). It can also be produced synthetically. Galantamine is used clinically for treating early-stage Alzheimer's disease and memory impairments, although it has had limited success with the more advanced condition of dementia. While the exact mechanism of galantamine in treating Alzheimer's disease is unknown, it is hypothesized to exert its therapeutic effects by enhancing cholinergic function. Galantamine inhibits the activity of acetylcholinesterase, an enzyme that catalyzes the breakdown of the neurotransmitter acetylcholine. This action elevates and prolongs synaptic acetylcholine concentrations, increasing the availability of acetylcholine to its receptors. The cholinergic system is involved in a variety of functions relevant to Alzheimer's symptomology, such as memory processing, reasoning, and thinking. Galantamine may cause serious adverse effects, such as stomach bleeding, liver injury or chest pain. Galantamine was isolated for the first time from bulbs of Galanthus nivalis (common snowdrop) in the Soviet Union in the 1940s. The active ingredient was extracted, identified, and studied, in particular in relation to acetylcholinesterase (AChE)-inhibiting properties. The first industrial process was developed in 1959. However, it was not until the 1990s when full-scale synthesis was upscaled and optimized.
Medical uses Galantamine, sold under the brand name Razadyne among others, is indicated for the treatment of mild to moderate vascular dementia and Alzheimer's disease. The first person to extract galantamine and theorize its usefulness in medicine, was the Bulgarian chemist Dimitar Paskov in 1959. In the United States, it is approved by the Food and Drug Administration (FDA) for the treatment of mild to moderate dementia. Galantamine may not be effective for treating mild cognitive impairment.
Alzheimer's disease Alzheimer's disease is characterized by the impairment of cholinergic function. One hypothesis is that this impairment contributes to the cognitive deficits caused by the disease. This hypothesis forms the basis for use of galantamine as a cholinergic enhancer in the treatment of Alzheimer's. Galantamine inhibits acetylcholinesterase, an enzyme which hydrolyzes acetylcholine. As a result of acetylcholinesterase inhibition, galantamine increases the availability of acetylcholine for synaptic transmission. Additionally, galantamine binds to the allosteric sites of nicotinic receptors, which causes a conformational change. This allosteric modulation increases the nicotinic receptor's response to acetylcholine. The activation of presynaptic nicotinic receptors increases the release of acetylcholine, further increasing the availability of acetylcholine. Galantamine's competitive inhibition of acetylcholinesterase and allosteric nicotinic modulation serves as a dual mechanism of action. To reduce the prevalence of negative side effects associated with galantamine, such as nausea and vomiting, a dose-escalation scheme may be used. The use of a dose-escalation scheme has been well accepted in countries where galantamine is used. A dose-escalation scheme for Alzheimer's treatment involves a recommended starting dosage of 4 mg galantamine tablets given twice a day (8 mg/day). After a minimum of 4 weeks, the dosage may then be increased to 8 mg given twice a day (16 mg/day). After a minimum of 4 weeks at 16 mg/day, the treatment may be increased to 12 mg given twice a day (24 mg/day). Dosage increases are based upon the assessment of clinical benefit as well as tolerability of the previous dosage. If treatment is interrupted for more than three days, the process is usually restarted, beginning at the starting dosage, and re-escalating to the current dose. It has been found that a dosage between 16–24 mg/day is the optimal dosage. In December 2023, the FDA approved a New Drug Application (NDA) for a pro-drug of galantamine called ALPHA-1062. In July 2024, The FDA approved benzgalantamine (Zunveyl, a derivative of galantamine), previously known as ALPHA-1062, to treat mild-to-moderate Alzheimer's disease.
Side effects The adverse effect profile of galantamine includes potential for allergic reaction, including hives, swelling of the face or throat, and skin rash. Using galantamine may cause chest pain, bloody urine, stomach bleeding, and liver injury, among other side effects. Nausea, vomiting, diarrhea, dizziness, and headache are considered common side effects. A gradual titration over more than three months may enable long-term tolerability in some people. Galantamine has a wide spectrum of interactions with other medications and medical disorders, requiring close assessment between the physician and patient.
Pharmacology Galantamine's chemical structure contains a tertiary amine. At a neutral pH, this tertiary amine will often bond to a proton, and appear mostly as an ammonium ion. Galantamine is a potent allosteric potentiating ligand of human nicotinic acetylcholine receptors (nAChRs) α4β2, α3β4, and α6β4, and chicken/mouse nAChRs α7/5-HT3 in certain areas of the brain. By binding to the allosteric site of the nAChRs, a conformational change occurs which increases the receptors response to acetylcholine. This modulation of the nicotinic cholinergic receptors on cholinergic neurons in turn causes an increase in the amount of acetylcholine released. However, recent studies suggest that Galantamine does not functionally act at human nAChRs α4β2 or α7 as a positive allosteric modulator. Galantamine also works as a weak competitive and reversible cholinesterase inhibitor in all areas of the body. By inhibiting acetylcholinesterase, it increases the concentration and thereby action of acetylcholine in certain parts of the brain. Galantamine's effects on nAChRs and complementary acetylcholinesterase inhibition make up a dual mechanism of action. It is hypothesized that this action might relieve some of the symptoms of Alzheimer's.
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