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Galantamine
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Other Names
Galantamine is marketed by Ortho-McNeil and sold under the following names:
- Razadyne (or Razadyne ER, an extended release form)
- Reminyl
- Nivalin
Uses
Galantamine is indicated for the treatment of dementia in people with mild to moderate AD.
How Galantamine is Taken
Galantamine is available in tablets of 4 mg, 8 mg, 12 mg, and an oral solution of 4 mg/ml. The recommended starting dose is 4 mg twice a day. The dose may be increased to 8 mg twice a day after a minimum of four weeks. The dose may be further increase to 12 mg twice daily after at least four weeks. Dosage increases are based on effectiveness and safety.
Razadyne ER is an extended release form of galantamine and is formulated to be taken once daily. It is available in capsules of 8 mg, 16 mg, and 24 mg.
How Galantamine Works
The precise cause of dementia in AD is not known. However, the disease is characterized by degeneration of neurons that release the neurotransmitter acetylcholine. An enzyme called acetylcholinesterase breaks down acetylcholine, thus deactivating the neurotransmitter. By inhibiting acetylcholinesterase, galantamine elevates acetylcholine levels in the brain, thereby offsetting some of the deficits caused by loss of the acetylcholine-producing brain cells in AD.
How the Body Affects Galantamine
Galantamine is rapidly absorbed with peak circulating levels reached at about one hour. The dose is most effective at this time. The time needed for the concentration of the drug in the blood to be reduced by half, the half-life, is approximately seven hours. Galantamine is metabolized in the liver by enzymes called CYP2D6 and CYP3A4. More than 90% of a dose is excreted in the urine.
Effect of genetics
The CYP2D6 gene is subject to mutations that reduce its ability to metabolize drugs. People who have mutations in the gene are called poor metabolizers. Those with a normal gene are called extensive metabolizers. A study has shown that levels of galantamine are higher in poor metabolizers compared to extensive metabolizers.[1] However, this is not expected to influence outcome of treatment since the safest and most effective dose is used.
Side Effects
The most common side effects of galantamine include the following:
Risks and Precautions
In 2005, The U.S. Food and Drug Administration had warned that galantamine may increase the risk of premature death in some patients.[2] However, a 2008 analysis of 12 clinical trials found no increased risk of mortality in patients treated with galantamine for less than or more than six months.[3]
Galantamine may cause dizziness and could hinder driving or other activities that require alertness.
Drug Interactions
Other drugs used to treat AD are likely to interact with galantamine. Sometimes combinations of these drugs are used to improve outcome.
Drugs that inhibit CYP2D6 or CYP3A4 may increase blood concentrations of galantamine. Some antifungals (e.g., ketoconazole (Nizoral), itraconazole (Sporanox)) and antibiotics (e.g., erythromycin) inhibit CYP3A4. The antidepressant paroxetine (Paxil) inhibits CYP2D6. The ulcer drug cimetidine (Tagamet) inhibits both these enzymes.
History and Development
Galantamine was isolated in the 1950s from the Caucasian snowdrop, Lycoris radiate, Galanthus woronowii, and some other species. Janssen Pharma developed galantamine, which was approved for use in the United States in 2001. Ortho-McNeil now markets galantamine, whereas galantamine in combinaiton with L-Alpha Glycerylphosphorylcholine is sold by CerebralHealth.
Alternatives
Galantamine is also available in a combination formulation with L-Alpha Glycerylphosphorylcholine, which is sold under the name Memeron. L-Alpha Glycerylphosphorylcholine is an acetylcholine precursor and may help elevate acetylcholine levels by increasing its production.
Research
Patients taking galantamine continuously throughout two long-term studies showed sustained cognitive benefits on test scores at 18.5 months post-start.[4] However, the response to cholinesterase inhibitors is quite variable, as recently reviewed by Takeda et al.[5] who note that “some patients will have improved, others stayed the same, while others will have deteriorated. This variance should be comparative in both the treatment and the placebo groups but care should be taken over the interpretation of the mean scores." Further research to identify AD patients likely to respond to cholinesterase inhibitor therapy is needed.
References
- ↑ Mannens GS, Snel CA, Hendrickx J, et al. The metabolism and excretion of galantamine in rats, dogs, and humans. Drug Metab Dispos. 2002 May;30(5):553-63.Abstract | Full Text | PDF
- ↑ FDA Center for Drug Evaluation and Research. Galantamine(marketed as Reminyl) Information
- ↑ Feldman HH, Pirttila T, Dartigues JF, et al. Analyses of mortality risk in patients with dementia treated with galantamine. Acta Neurol Scand. 2008 Jun 1. Abstract
- ↑ Lyketsos CG, Reichman WE, Kershaw P, Zhu Y. Long-term outcomes of galantamine treatment in patients with Alzheimer disease. Am J Geriatr Psychiatry. 2004 Sep-Oct;12(5):473-82. Abstract
- ↑ Takeda A, Loveman E, Clegg A, et al. A systematic review of the clinical effectiveness of donepezil, rivastigmine and galantamine on cognition, quality of life and adverse events in Alzheimer's disease. Int J Geriatr Psychiatry. 2006 Jan;21(1):17-28. Abstract
External Links
FDA: Patient Information Sheet
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The content on or accessible through Medpedia.com is for informational purposes only. Medpedia is not a substitute for professional advice or expert medical services from a qualified health professional.
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