Galanthamine

Absorption

Over a dose range of 8-32 mg/day, galantamine exhibits a dose-linear pharmacokinetic profile. The oral bioavailability of galantamine ranges from 90-100%. Following oral administration, the Tmax is about 1 hour. Following 10 hours of administration, the mean galantamine plasma concentrations were 82–97 μg/L for the 24 mg/day dose and 114–126 μg/L for the 32 mg/day dose.

Toxicity

The oral LD50 of the active ingredient, galantamine hydrobromide, in rats is 75 mg/kg. Symptoms of overdose are expected to be similar to those of cholinomimetics, which involve the central nervous system, the parasympathetic nervous system, and the neuromuscular junction. Effects of a cholinergic crisis include severe nausea, vomiting, gastrointestinal cramping, salivation, lacrimation, urination, defecation, sweating, bradycardia, hypotension, respiratory depression, collapse, and convulsions. Muscle weakness or fasciculations may also occur, with respiratory muscle weakness having the potential to bring fatal results. In one patient who consumed an oral daily dose of 32 mg developed bradycardia, QT prolongation, ventricular tachycardia and torsades de pointes accompanied by a brief loss of consciousness. In one patient with a history of hallucinations who consumed a daily dose of 24 mg galantamine, hallucinations requiring hospitalization occurred. A patient who ingested 160 mg of galantamine from an oral solution developed sweating, vomiting, bradycardia, and near-syncope one hour following consumption.
As in any case of overdose, general supportive measures should be initiated. Tertiary anticholinergics such as intravenous atropine may be used to reverse the cholinergic effects of galantamine. The recommended initial dose of atropine intravenously administered for galantamine overdose ranges from 0.5 to 1.0 mg. It is not known whether galantamine can be removed by dialysis.

Description

Galantamine is an Amaryllidaceae alkaloid which is first obtained from the plant of snowdrop (Galanthus nivalis), and nowadays, it’s extracted from the plants of Narcissus and Galanthus species or obtained from chemosynthesis. In many areas in Europe such as Bulgaria, eastern Turkey, and the Caucasus, the plants of Galanthus are native species. But its earliest pharmaceutical applications are seldom known. Plaitakis and Duvoisin hypothesized that “moly” in ancient Homer’s epic might be snowdrops. In Homer’s epic Odyssey, “moly” was used as an antidote by Odysseus against Circe’s poisonous drugs. To be used as an antidote may be the plants of Galanthus’ oldest medicinal records. But there is not much evidence for that. There is little evidence of the traditional application of the plants of Galanthus, and it is certain that until the Second World War, the plants of Galanthus and other genera of Amaryllidaceae were not frequently used in European drugs
Italian scholar Iannello studied Pancratium illyricum L., an Amaryllidaceae species endemic to Sardinia, and isolated a new galantamine-type alkaloid in its leaves. This new galantamine-type compound exhibited a pronounced in?vitro AChE inhibitory activity (IC50? =? 3.5±1.1? μM) in comparison with the reference standard galantamine hydrobromide (IC50?=?1.5±0.2?μM)

Chemical properties

Off-White Solid

Physical properties

Hydrobromide of galantamine can be used as drug although galantamine can’t be used as drugs
Appearance: an almost white powder. Solubility: soluble in water; slightly soluble in alcohol; and insoluble in acetone, trichloromethane, and diethyl ether. Melting point: 269–270?°C. Specific optical rotation: ?90 to ?100°.

Originator

Reminyl,Janssen Pharmaceutica Inc.

Occurrence

Galanthamine is a bulb plant found throughout the world.

History

In the early 1950s, Soviet Union’s scientists started modern medicine research of galantamine. In 1951, the Soviet Union’s pharmacologist Mashkovsky and Kruglikova-Lvova firstly proved its AChE-inhibiting properties, which was published in the paper. In 1957, the Bulgarian pharmacologist Paskov et?al. found that the plants of Galanthus were the richest sources of galantamine, which opened a way for its commercial development by the company Sopharma in Bulgaria. Galantamine hydrobromide was launched into market under the trade name Nivalin. Initially, Nivalin was used in anesthesia to antagonize the effects of non-depolarizing muscle relaxants, and since then, it was rapidly introduced in other areas of medicine
Galantamine hydrobromide was launched into market for the indication of mild to moderate Alzheimer’s disease firstly in 1995, developed by Sanochemia Pharmaceuticals. In the United States, galantamine hydrobromide was developed by Janssen Pharmaceuticals, a subsidiary of Johnson & Johnson, and was listed under the trade name Razadyne in 2001. So far, galantamine hydrobromide has been marketed in more than 20 countries and regions, such as the United States, Europe, and Japan.

The Uses of Galanthamine

A selective acetylcholinesterase inhibitor. Useful for the treatment of Alzheimer's disease.

The Uses of Galanthamine

synthetic fluoroquinolone antibiotic agent

The Uses of Galanthamine

Galantamine is approved for the treatment of mild-to-moderate AD.It is a reversible specific inhibitor of AChE,and in addition it modulates central nicotinic receptors toincrease cholinergic neurotransmission.

Background

Galantamine is a tertiary alkaloid and reversible, competitive inhibitor of the acetylcholinesterase (AChE) enzyme, which is a widely studied therapeutic target used in the treatment of Alzheimer's disease. First characterized in the early 1950s, galantamine is a tertiary alkaloid that was extracted from botanical sources, such as Galanthus nivalis. Galantamine was first studied in paralytic and neuropathic conditions, such as myopathies and postpolio paralytic conditions, and for reversal of neuromuscular blockade. Following the discovery of its AChE-inhibiting properties, the cognitive effects of galantamine were studied in a wide variety of psychiatric disorders such as mild cognitive impairment, cognitive impairment in schizophrenia and bipolar disorder, and autism; however, re-development of the drug for Alzheimer’s disease did not commence until the early 1990s due to difficulties in extraction and synthesis. Galantamine blocks the breakdown of acetylcholine in the synaptic cleft, thereby increasing acetylcholine neurotransmission. It also acts as an allosteric modulator of the nicotinic receptor, giving its dual mechanism of action clinical significance.
The drug was approved by the FDA in 2001 for the treatment of mild to moderate dementia of the Alzheimer's type. As Alzheimer's disease is a progressive neurodegenerative disorder, galantamine is not known to alter the course of the underlying dementing process. Galantamine works to block the enzyme responsible for the breakdown of acetylcholine in the synaptic cleft, thereby enhancing cholinergic neuron function and signalling. Under this hypothesized mechanism of action, the therapeutic effects of galantamine may decrease as the disease progression advances and fewer cholinergic neurons remain functionally intact. It is therefore not considered to be a disease-modifying drug. Galantamine is marketed under the brand name Razadyne, and is available as oral immediate- and extended-release tablets and solution.

What are the applications of Application

Galanthamine is a selective acetylcholinesterase inhibitor

What are the applications of Application

Galanthamine hydrochloride is a selective inhibitor of AChE (acetylcholinesterase)

Indications

Galantamine is indicated for the treatment of mild to moderate dementia of the Alzheimer’s type.

Definition

ChEBI: A natural product found in Crinum asiaticum var. sinicum.

Indications

Its formulation includes capsule, tablet, and oral solution. It is used in the symptomatic treatment of mild to moderately severe dementia in Alzheimer’s disease.

Manufacturing Process

2 Methods of isolation of galantamine from Narcissus pseudonarcissus bulbs 1. 10 kg air-dried, comminuted bulbs of Narcissus pseudonarcissus "Carlton" is carefully mixed with 400 g sodium carbonate. 23 L dichloroethane is added. The mixture is allowed to stand for 10 h; then the solvent is decanted. The bulbs are once again doused with 23 L dichloroethane which is decanted after 2 to 3 hs. After that, 17 L dichloroethane is added to the bulbs for the third time; however, this is decanted immediately. The mixed dichloroethane extracts are extracted by means of 10% sulfuric acid (2 times 600 ml each; 2 times 300 ml each).
The acidic extracts are mixed and purified from traces of dichloroethane by means of shaking out with diethyl ether. Under stirring and cooling to 15° to 20°C, about 200 ml of a 25% aqueous ammonia solution is then added up to alkaline litmus reaction (the pH is in the range of 7 to 8). Different from the indications in the art, the companion alkaloids do not precipitate. The alkaline solution is saturated with salt and extracted with diethyl ether.
After evaporation of the ether, a negligible residue remains, which is also different from the indications in the art. The pH-value of the aqueous phase is set to about 14 by saturating it with potash. The aqueous phase is repeatedly extracted with diethyl ether. The mixed ether extracts are evaporated to dryness, the remaining galanthamine-containing residue is dissolved in acetone (50 ml). In contrast to the art, there is no precipitate. 350 ml acetone is replenished, 200 g aluminum oxide is added, and stirring is effected for 45 min. The aluminum oxide is filtered off and washed twice with 100 ml acetone each time. The mixed acetone solutions are evaporated to dryness. 1.3 g of an oily residue is obtained which is examined by means of HPLC.
2. 100 kg air-dried, comminuted bulbs of Narcissus pseudonarcissus "Carlton" is carefully mixed with 4 kg of sodium carbonate. The mixture is divided into three equal parts, and each is doused with 15 L special boiling-point gasoline 80/110. The mixtures are allowed to stand for 24 hs. The solvents are each renewed twice, collected, and evaporated to dryness in low vacuum. The extracts are placed in 2% aqueous sulfuric acid and adjusted to a pH of 4 with concentrated aqueous ammonia solution. Five extractions with diethyl ether follow. The aqueous phase is set to a pH of 9 with concentrated ammonia and extracted five times with diethyl ether. These ether fractions are collected, dried with sodium sulfate, and evaporated. 20 g of a slightly yellow, oily residue is obtained, which is recrystallized from hot isopropanol. 10 g of white galanthamine base having a melting point of 129°-130°C is obtained.
Galantamine may be isolated from Galanthus nivalis or G. woronowi bulbs too.

Therapeutic Function

Cholinesterase inhibitor

General Description

Galantamine, 4a,5,9,10,11,12-hexahydro-3-methoxy-11-methyl-6H-benzofuro-[3a,3,2,ef][2]-benzazepin-6-ol (Nivalin, Reminyl), is an alkaloid extractedfrom the tuberous plant Leucojum aestivum (L.) belongingto the Amaryllidaceae family and from the bulbs of thedaffodil, Narcissus pseudonarcissus. It is a reversiblecholinesterase inhibitor that appears to have no effect on butyrylcholinesterase.In addition, it acts at allosteric nicotinicsites, further enhancing its cholinergic activity. Galantamineundergoes slow and minor biotransformation with approximately5% to 6% undergoing demethylation. It is primarilyexcreted in the urine.

Pharmacokinetics

Galantamine is a competitive and reversible inhibitor of acetylcholinesterase that works to increase acetylcholine levels. Galantamine acts both centrally and peripherally to inhibit both muscle and brain acetylcholinesterase, thereby increasing cholinergic tone. Galantamine is also a positive allosteric modulator of neuronal nicotinic acetylcholine receptors. As dementia is a progressive neurodegenerative disease, galatamine has a negligible effect in altering the course of the underlying process of dementia and may exert its therapeutic effectiveness for a short period of time. However, galantamine promoted improvements in cognition, global function, activities of daily living, and behavioural symptoms in clinical studies of Alzheimer’s disease.
Galantamine exhibited therapeutic efficacy in studies of vascular dementia and Alzheimer’s disease with cerebrovascular disease. In one study, galantamine reversed scopolamine-induced acute anticholinergic syndrome that was characterized by drowsiness, disorientation, and delirium.

Pharmacology

hydrolyzed and metabolized by AChE.?When AD occurs, neurons in the basal forebrain region of the brain are lost, resulting in the reduction of synthesis, storage and release of ACh, which leads to a variety of clinical manifestations especially memory and recognition dysfunction. Galantamine is a reversible AChE inhibitor, which is highly selective and competitive. It competitively binds to AChE in a synaptic gap with Ach, blocks the degradation of Ach by AChE, and thus achieves efficacy. Besides, it has the activity as an allosteric modulator of nicotinic acetylcholine receptor (nAChR). nAChR is mainly located in the muscarinic choline receptor’s presynaptic structure. It can promote the release of Ach, which is critical to maintain the survival and function of cholinergic neurons. The study found that in cerebral cortex of the patients of AD, nAChR was significantly reduced. Galantamine binds to AChR’s allosteric site to increase the transmission of acetylcholine signaling.
Galantamine has a 53-fold greater inhibitory activity in?vitro for AChE than for butyrylcholinesterase (BChE). The low affinity of galantamine for BChE may be responsible for a tolerability advantage. BChE, which is primarily found in plasma, is not thought to be directly involved in the cholinergic disruption seen in early AD, and its inhibition may contribute to peripheral side effects.
It was recorded in Martindale: The Complete Drug Reference that an initial oral dose of 4?mg is given twice daily with food for 4?weeks and then increased to 8?mg twice daily. This dose should be maintained for at least 4?weeks; thereafter, the dose may be further increased to 12?mg twice daily according to response and tolerance. The clinical benefit of galantamine should be reassessed, preferably within the first 3?months and thereafter on a regular basis
Galantamine is metabolized by hepatic cytochrome P450 enzymes CYP3A4 and CYP2D6, glucuronidated, and excreted unchanged in the urine. After intravenous injection or oral administration, about 20% of the dose was excreted as unchanged galantamine in the urine, and the other was metabolized by the hepar.

Clinical Use

Before the 1990s, galantamine was mainly used to treat poliomyelitis sequelae, muscle atrophy, postoperative intestinal muscle paralysis, urinary retention, and myasthenia gravis. In the 1990s, it was found that galantamine had improved memory impairment in mice, suggesting that it might be effective for central cholinergic disorders in Alzheimer’s disease
In a 3–6?months’ well-designed clinical trial, recipients of galantamine achieved significant improvements in cognitive symptoms compared to placebo recipients. Galantamine also improved activities of daily living in these patients and significantly reduced the requirement for caregiver assistance with activities of daily living. Clinical development of new indications of galanthamine is currently underway, such as smoking cessation and improving cognitive impairment in schizophrenia and mania.

Drug interactions

Potentially hazardous interactions with other drugs
Antibacterials: erythromycin increases concentration of galantamine.

Metabolism

In vitro study findings suggest that about 75% of the drug is metabolized by CYP2D6 and CYP3A4. CYP2D6 promotes O-demethylation of the drug to form O-desmethyl-galantamine and the CYP3A4-mediated pathway forms the galantamine-N-oxide. Important metabolic pathways also include N-demethylation, epimerization, and sulfate conjugation. Other metabolites include norgalantamine, O-desmethyl-galantamine, O-desmethyl-norgalantamine, epigalantamine and galantaminone, which do not retain clinically significant pharmacology activities.
Galantamine can also undergo glucuronidation: in one oral radiolabeled drug study in poor and extensive CYP2D6 metabolizers, about 14-24% of the total radioactivity was identified as galantamine glucuronide 8 hours post-dose. O-demethylation by CYP2D6 becomes prominent in patients with who are extensive metabolizers of CYP2D6, but unchanged galatamine (39-77%) and its glucuronide metabolite (14-24%) predominated in the plasma of both poor and extensive metabolizers of CYP2D6 in a radiolabelled drug study. The total plasma clearance, or nonrenal clearnace, accounts for 20–25% of drug elimination.

Metabolism

Galantamine is partially (up to 75%) metabolised by the cytochrome P450 isoenzymes CYP2D6 and CYP3A4; a number of active metabolites are formed.
After 7 days, 90-97% of a single oral dose is recovered in the urine with up to about 6% detected in the faeces; about 20-30% of the dose is excreted in the urine as unchanged galantamine. Clearance is reported to be 20% lower in females than in males and 25% lower in poor metabolisers than in extensive metabolisers.