Galantamine hydrobromide, USP is a reversible, competitive acetylcholinesterase inhibitor. It is known chemically as (4aS,6R,8aS)-4a,5,9,10,11,12-hexahydro-3-methoxy-11-methyl-6H-benzofuro[3a,3,2-ef][2]benzazepin-6-ol hydrobromide. It has a molecular formula of C17H21NO3 •HBr and a molecular weight of 368.27. Galantamine hydrobromide is a white to off-white powder and is sparingly soluble in water. The structural formula for Galantamine hydrobromide is:
Galantamine tablets for oral use are available in blue film-coated, round tablets of 4 mg, 8 mg or 12 mg. Each 4 mg, 8 mg and 12 mg (base equivalent) tablet contains 5.126 mg, 10.253 mg and 15.379 mg of Galantamine hydrobromide, respectively. Inactive ingredients include colloidal silicon dioxide, FD&C Blue No. 2 Aluminum Lake, hypromellose, magnesium stearate, microcrystalline cellulose, polydextrose, polyethylene glycol, sodium lauryl sulfate, sodium starch glycolate, titanium dioxide and triacetin.
Galantamine - Clinical Pharmacology
Mechanism of Action
Although the etiology of cognitive impairment in Alzheimer's disease (AD) is not fully understood, it has been reported that acetylcholine-producing neurons degenerate in the brains of patients with Alzheimer's disease. The degree of this cholinergic loss has been correlated with degree of cognitive impairment and density of amyloid plaques (a neuropathological hallmark of Alzheimer's disease).
Galantamine, a tertiary alkaloid, is a competitive and reversible inhibitor of acetylcholinesterase. While the precise mechanism of Galantamine's action is unknown, it is postulated to exert its therapeutic effect by enhancing cholinergic function. This is accomplished by increasing the concentration of acetylcholine through reversible inhibition of its hydrolysis by cholinesterase. If this mechanism is correct, Galantamine's effect may lessen as the disease process advances and fewer cholinergic neurons remain functionally intact. There is no evidence that Galantamine alters the course of the underlying dementing process.
Pharmacokinetics
Galantamine is well absorbed with absolute oral bioavailability of about 90%. It has a terminal elimination half-life of about 7 hours and pharmacokinetics are linear over the range of 8 to 32 mg/day.
The maximum inhibition of acetylcholinesterase activity of about 40% was achieved about one hour after a single oral dose of 8 mg Galantamine in healthy male subjects.
Absorption and DistributionGalantamine is rapidly and completely absorbed with time to peak concentration about one hour. Bioavailability of the tablet was the same as the bioavailability of an oral solution. Food did not affect the AUC of Galantamine but Cmax decreased by 25% and Tmax was delayed by 1.5 hours. The mean volume of distribution of Galantamine is 175 L.
The plasma protein binding of Galantamine is 18% at therapeutically relevant concentrations. In whole blood, Galantamine is mainly distributed to blood cells (52.7%). The blood to plasma concentration ratio of Galantamine is 1.2.
Metabolism and EliminationGalantamine is metabolized by hepatic cytochrome P450 enzymes, glucuronidated, and excreted unchanged in the urine. In vitro studies indicate that cytochrome CYP2D6 and CYP3A4 were the major cytochrome P450 isoenzymes involved in the metabolism of Galantamine, and inhibitors of both pathways increase oral bioavailability of Galantamine modestly (see PRECAUTIONS: Drug-Drug Interactions). O-demethylation, mediated by CYP2D6 was greater in extensive metabolizers of CYP2D6 than in poor metabolizers. In plasma from both poor and extensive metabolizers, however, unchanged Galantamine and its glucuronide accounted for most of the sample radioactivity.
In studies of oral 3H-Galantamine, unchanged Galantamine and its glucuronide, accounted for most plasma radioactivity in poor and extensive CYP2D6 metabolizers. Up to 8 hours post-dose, unchanged Galantamine accounted for 39% to 77% of the total radioactivity in the plasma, and Galantamine glucuronide for 14% to 24%. By 7 days, 93% to 99% of the radioactivity had been recovered, with about 95% in urine and about 5% in the feces. Total urinary recovery of unchanged Galantamine accounted for, on average, 32% of the dose and that of Galantamine glucuronide for another 12% on average.
After i.v. or oral administration, about 20% of the dose was excreted as unchanged Galantamine in the urine in 24 hours, representing a renal clearance of about 65 mL/min, about 20% to 25% of the total plasma clearance of about 300 mL/min.
Special Populations
CYP2D6 Poor MetabolizersApproximately 7% of the normal population has a genetic variation that leads to reduced levels of activity of CYP2D6 isozyme. Such individuals have been referred to as poor metabolizers. After a single oral dose of 4 mg or 8 mg Galantamine, CYP2D6 poor metabolizers demonstrated a similar Cmax and about 35% AUC∞ increase of unchanged Galantamine compared to extensive metabolizers.
A total of 356 patients with Alzheimer's disease enrolled in two Phase 3 studies were genotyped with respect to CYP2D6 (n = 210 hetero-extensive metabolizers, 126 homo-extensive metabolizers, and 20 poor metabolizers). Population pharmacokinetic analysis indicated that there was a 25% decrease in median clearance in poor metabolizers compared to extensive metabolizers. Dosage adjustment is not necessary in patients identified as poor metabolizers as the dose of drug is individually titrated to tolerability.
Hepatic ImpairmentFollowing a single 4 mg dose of Galantamine tablets, the pharmacokinetics of Galantamine in subjects with mild hepatic impairment (n = 8; Child-Pugh score of 5 to 6) were similar to those in healthy subjects. In patients with moderate hepatic impairment (n = 8; Child-Pugh score of 7 to 9), Galantamine clearance was decreased by about 25% compared to normal volunteers. Exposure would be expected to increase further with increasing degree of hepatic impairment (see PRECAUTIONS and DOSAGE AND ADMINISTRATION).
Renal ImpairmentFollowing a single 8 mg dose of Galantamine tablets, AUC increased by 37% and 67% in moderate and severely renal impaired patients compared to normal volunteers (see PRECAUTIONS and DOSAGE AND ADMINISTRATION).
ElderlyData from clinical trials in patients with Alzheimer's disease indicate that Galantamine concentrations are 30% to 40% higher than in healthy young subjects.
Gender and RaceNo specific pharmacokinetic study was conducted to investigate the effect of gender and race on the disposition of Galantamine, but a population pharmacokinetic analysis indicates (n = 539 males and 550 females) that Galantamine clearance is about 20% lower in females than in males (explained by lower body weight in females) and race (n = 1,029 White, 24 Black, 13 Asian and 23 other) did not affect the clearance of Galantamine.
Drug-Drug Interactions
(see also PRECAUTIONS: Drug-Drug Interactions)
Multiple metabolic pathways and renal excretion are involved in the elimination of Galantamine so no single pathway appears predominant. Based on in vitro studies, CYP2D6 and CYP3A4 were the major enzymes involved in the metabolism of Galantamine. CYP2D6 was involved in the formation of O-desmethyl-Galantamine, whereas CYP3A4 mediated the formation of Galantamine-N-oxide. Galantamine is also glucuronidated and excreted unchanged in urine.
Effect of Other Drugs on the Metabolism of GalantamineDrugs that are potent inhibitors for CYP2D6 or CYP3A4 may increase the AUC of Galantamine. Multiple dose pharmacokinetic studies demonstrated that the AUC of Galantamine increased 30% and 40%, respectively, during coadministration of ketoconazole and paroxetine. As coadministered with erythromycin, another CYP3A4 inhibitor, the Galantamine AUC increased only 10%. Population PK analysis with a database of 852 patients with Alzheimer's disease showed that the clearance of Galantamine was decreased about 25% to 33% by concurrent administration of amitriptyline (n = 17), fluoxetine (n = 48), fluvoxamine (n = 14), and quinidine (n = 7), known inhibitors of CYP2D6.
Concurrent administration of H2-antagonists demonstrated that ranitidine did not affect the pharmacokinetics of Galantamine, and cimetidine increased the Galantamine AUC by approximately 16%. A multiple dose pharmacokinetic study with concurrent administration of memantine, an N-methyl-D-aspartate (NMDA) receptor antagonist, demonstrated that coadministration of memantine in a dose of 10 mg BID did not affect the pharmacokinetic profile of Galantamine (16 mg daily) at steady-state.
Effect of Galantamine on the Metabolism of Other DrugsIn vitro studies show that Galantamine did not inhibit the metabolic pathways catalyzed by CYP1A2, CYP2A6, CYP3A4, CYP4A, CYP2C, CYP2D6 and CYP2E1. This indicated that the inhibitory potential of Galantamine towards the major forms of cytochrome P450 is very low. Multiple doses of Galantamine (24 mg/day) had no effect on the pharmacokinetics of digoxin and warfarin (R- and S-forms). Galantamine had no effect on the increased prothrombin time induced by warfarin.
Clinical Trials
The effectiveness of Galantamine hydrobromide as a treatment for Alzheimer's disease is demonstrated by the results of five randomized, double-blind, placebo-controlled clinical investigations in patients with probable Alzheimer's disease, four with the immediate-release tablet and one with the extended-release capsule [diagnosed by NINCDS-ADRDA criteria, with Mini-Mental State Examination scores that were ≥ 10 and ≤ 24]. Doses studied with the tablet formulation were 8 to 32 mg/day given as twice daily doses. In 3 of the 4 studies with the tablet, patients were started on a low dose of 8 mg, then titrated weekly by 8 mg/day to 24 mg or 32 mg as assigned. In the fourth study (USA 4-week Dose-Escalation Fixed-Dose Study) dose escalation of 8 mg/day occurred over 4 week intervals. The mean age of patients participating in these four Galantamine trials was 75 years with a range of 41 to 100. Approximately 62% of patients were women and 38% were men. The racial distribution was White 94%, Black 3% and other races 3%. Two other studies examined a 3 times daily dosing regimen; these also showed or suggested benefit but did not suggest an advantage over twice daily dosing.
Study Outcome Measures
In each study, the primary effectiveness of Galantamine was evaluated using a dual outcome assessment strategy as measured by the Alzheimer's Disease Assessment Scale (ADAS-cog) and the Clinician's Interview Based Impression of Change that required the use of caregiver information (CIBIC-plus).
The ability of Galantamine to improve cognitive performance was assessed with the cognitive sub-scale of the Alzheimer's Disease Assessment Scale (ADAS-cog), a multi-item instrument that has been extensively validated in longitudinal cohorts of Alzheimer's disease patients. The ADAS-cog examines selected aspects of cognitive performance including elements of memory, orientation, attention, reasoning, language and praxis. The ADAS-cog scoring range is from 0 to 70, with higher scores indicating greater cognitive impairment. Elderly normal adults may score as low as 0 or 1, but it is not unusual for non-demented adults to score slightly higher.
The patients recruited as participants in each study using the tablet formulation had mean scores on ADAS-cog of approximately 27 units, with a range from 5 to 69. Experience gained in longitudinal studies of ambulatory patients with mild to moderate Alzheimer's disease suggests that they gain 6 to 12 units a year on the ADAS-cog. Lesser degrees of change, however, are seen in patients with very mild or very advanced disease because the ADAS-cog is not uniformly sensitive to change over the course of the disease. The annualized rate of decline in the placebo patients participating in Galantamine trials was approximately 4.5 units per year.
The ability of Galantamine to produce an overall clinical effect was assessed using a Clinician's Interview Based Impression of Change that required the use of caregiver information, the CIBIC-plus. The CIBIC-plus is not a single instrument and is not a standardized instrument like the ADAS-cog. Clinical trials for investigational drugs have used a variety of CIBIC formats, each different in terms of depth and structure. As such, results from a CIBIC-plus reflect clinical experience from the trial or trials in which it was used and can not be compared directly with the results of CIBIC-plus evaluations from other clinical trials. The CIBIC-plus used in the trials was a semi-structured instrument based on a comprehensive evaluation at baseline and subsequent time-points of four major areas of patient function: general, cognitive, behavioral and activities of daily living. It represents the assessment of a skilled clinician based on his/her observation at an interview with the patient, in combination with information supplied by a caregiver familiar with the behavior of the patient over the interval rated. The CIBIC-plus is scored as a seven point categorical rating, ranging from a score of 1, indicating "markedly improved," to a score of 4, indicating "no change" to a score of 7, indicating "marked worsening." The CIBIC-plus has not been systematically compared directly to assessments not using information from caregivers (CIBIC) or other global methods.
U.S. Twenty-One Week-Fixed-Dose Study
In a study of 21 weeks duration, 978 patients were randomized to doses of 8 mg, 16 mg, or 24 mg of Galantamine hydrobromide per day, or to placebo, each given in two divided doses. Treatment was initiated at 8 mg/day for all patients randomized to Galantamine hydrobromide and increased by 8 mg/day every 4 weeks. Therefore, the maximum titration phase was 8 weeks and the minimum maintenance phase was 13 weeks (in patients randomized to 24 mg/day of Galantamine hydrobromide.
Effects on the ADAS-cogFigure 1 illustrates the time course for the change from baseline in ADAS-cog scores for all four dose groups over the 21 weeks of the study. At 21 weeks of treatment, the mean differences in the ADAS-cog change scores for the Galantamine hydrobromide-treated patients compared to the patients on placebo were 1.7, 3.3, and 3.6 units for the 8, 16 and 24 mg/day treatments, respectively. The 16 mg/day and 24 mg/day treatments were statistically significantly superior to placebo and to the 8 mg/day treatment. There was no statistically significant difference between the 16 mg/day and 24 mg/day dose groups.
Figure 1: Time-Course of the Change From Baseline in ADAS-cog Score for Patients Completing 21 Weeks (5 Months) of Treatment
Figure 2 illustrates the cumulative percentages of patients from each of the four treatment groups who had attained at least the measure of improvement in ADAS-cog score shown on the X axis. Three change scores (10-point, 7-point and 4-point reductions) and no change in score from baseline have been identified for illustrative purposes, and the percent of patients in each group achieving that result is shown in the inset table.
The curves demonstrate that both patients assigned to Galantamine and placebo have a wide range of responses, but that the Galantamine groups are more likely to show the greater improvements.
Figure 2: Cumulative Percentage of Patients Completing 21 Weeks of Double-Blind Treatment With Specified Changes From Baseline in ADAS-cog Scores. The Percentages of Randomized Patients Who Completed the Study Were: Placebo 84%, 8 mg/day 77%, 16 mg/day 78% and 24 mg/day 78%.
Change in ADAS-cog
| Treatment |
-10 |
-7 |
-4 |
0 |
| Placebo |
3.6% |
7.6% |
19.6% |
41.8% |
| 8 mg/day |
5.9% |
13.9% |
25.7% |
46.5% |
| 16 mg/day |
7.2% |
15.9% |
35.6% |
65.4% |
| 24 mg/day |
10.4% |
22.3% |
37.0% |
64.9% |
Effects on the CIBIC-plusFigure 3 is a histogram of the percentage distribution of CIBIC-plus scores attained by patients assigned to each of the four treatment groups who completed 21 weeks of treatment. The Galantamine hydrobromide-placebo differences for these groups of patients in mean rating were 0.15, 0.41 and 0.44 units for the 8, 16 and 24 mg/day treatments, respectively. The 16 mg/day and 24 mg/day treatments were statistically significantly superior to placebo. The differences vs. the 8 mg/day treatment for the 16 and 24 mg/day treatments were 0.26 and 0.29, respectively. There were no statistically significant differences between the 16 mg/day and 24 mg/day dose groups.
Figure 3: Distribution of CIBIC-plus Ratings at Week 21
U.S. Twenty-Six Week-Fixed-Dose Study
In a study of 26 weeks duration, 636 patients were randomized to either a dose of 24 mg or 32 mg of Galantamine hydrobromide per day, or to placebo, each given in two divided doses. The 26-week study was divided into a 3-week dose titration phase and a 23-week maintenance phase.
Effects on the ADAS-cogFigure 4 illustrates the time course for the change from baseline in ADAS-cog scores for all three dose groups over the 26 weeks of the study. At 26 weeks of treatment, the mean differences in the ADAS-cog change scores for the Galantamine hydrobromide-treated patients compared to the patients on placebo were 3.9 and 3.8 units for the 24 mg/day and 32 mg/day treatments, respectively. Both treatments were statistically significantly superior to placebo, but were not significantly different from each other.
Figure 4: Time-Course of the Change From Baseline in ADAS-cog Score for Patients Completing 26 Weeks of Treatment
Figure 5 illustrates the cumulative percentages of patients from each of the three treatment groups who had attained at least the measure of improvement in ADAS-cog score shown on the X axis. Three change scores (10-point, 7-point and 4-point reductions) and no change in score from baseline have been identified for illustrative purposes, and the percent of patients in each group achieving that result is shown in the inset table.
The curves demonstrate that both patients assigned to Galantamine and placebo have a wide range of responses, but that the Galantamine groups are more likely to show the greater improvements. A curve for an effective treatment would be shifted to the left of the curve for placebo, while an ineffective or deleterious treatment would be superimposed upon, or shifted to the right of the curve for placebo, respectively.
Figure 5: Cumulative Percentage of Patients Completing 26 Weeks of Double-Blind Treatment With Specified Changes From Baseline in ADAS-cog Scores. The Percentages of Randomized Patients Who Completed the Study Were: Placebo 81%, 24 mg/day 68%, and 32 mg/day 58%.
Change in ADAS-cog
| Treatment |
-10 |
-7 |
-4 |
0 |
| Placebo |
2.1% |
5.7% |
16.6% |
43.9% |
| 24 mg/day |
7.6% |
18.3% |
33.6% |
64.1% |
| 32 mg/day |
11.1% |
19.7% |
33.3% |
58.1% |
Effects on the CIBIC-plusFigure 6 is a histogram of the percentage distribution of CIBIC-plus scores attained by patients assigned to each of the three treatment groups who completed 26 weeks of treatment. The mean Galantamine hydrobromide-placebo differences for these groups of patients in the mean rating were 0.28 and 0.29 units for 24 and 32 mg/day of Galantamine hydrobromide, respectively. The mean ratings for both groups were statistically significantly superior to placebo, but were not significantly different from each other.
Figure 6: Distribution of CIBIC-plus Ratings at Week 26
International Twenty-Six-Week Fixed-Dose Study
In a study of 26 weeks duration identical in design to the USA 26-Week Fixed-Dose Study, 653 patients were randomized to either a dose of 24 mg or 32 mg of Galantamine hydrobromide per day, or to placebo, each given in two divided doses. The 26-week study was divided into a 3-week dose titration phase and a 23-week maintenance phase.
Effects on the ADAS-cogFigure 7 illustrates the time course for the change from baseline in ADAS-cog scores for all three dose groups over the 26 weeks of the study. At 26 weeks of treatment, the mean differences in the ADAS-cog change scores for the Galantamine hydrobromide-treated patients compared to the patients on placebo were 3.1 and 4.1 units for the 24 mg/day and 32 mg/day treatments, respectively. Both treatments were statistically significantly superior to placebo, but were not significantly different from each other.
Figure 7: Time-Course of the Change From Baseline in ADAS-cog Score for Patients Completing 26 Weeks of Treatment
Figure 8 illustrates the cumulative percentages of patients from each of the three treatment groups who had attained at least the measure of improvement in ADAS-cog score shown on the X axis. Three change scores (10-point, 7-point and 4-point reductions) and no change in score from baseline have been identified for illustrative purposes, and the percent of patients in each group achieving that result is shown in the inset table.
The curves demonstrate that both patients assigned to Galantamine and placebo have a wide range of responses, but that the Galantamine groups are more likely to show the greater improvements.
Figure 8: Cumulative Percentage of Patients Completing 26 Weeks of Double-Blind Treatment With Specified Changes From Baseline in ADAS-cog Scores. The Percentages of Randomized Patients Who Completed the Study Were: Placebo 87%, 24 mg/day 80%, and 32 mg/day 75%.
Change in ADAS-cog
| Treatment |
-10 |
-7 |
-4 |
0 |
| Placebo |
1.2% |
5.8% |
15.2% |
39.8% |
| 24 mg/day |
4.5% |
15.4% |
30.8% |
65.4% |
| 32 mg/day |
7.9% |
19.7% |
34.9% |
63.8% |
Effects on the CIBIC-plusFigure 9 is a histogram of the percentage distribution of CIBIC-plus scores attained by patients assigned to each of the three treatment groups who completed 26 weeks of treatment. The mean Galantamine hydrobromide-placebo differences for these groups of patients in the mean rating of change from baseline were 0.34 and 0.47 for 24 and 32 mg/day of Galantamine hydrobromide, respectively. The mean ratings for the Galantamine groups were statistically significantly superior to placebo, but were not significantly different from each other.
Figure 9: Distribution of CIBIC-plus Rating at Week 26
International Thirteen-Week Flexible-Dose Study
In a study of 13 weeks duration, 386 patients were randomized to either a flexible dose of 24 to 32 mg/day of Galantamine hydrobromide or to placebo, each given in two divided doses. The 13-week study was divided into a 3-week dose titration phase and a 10-week maintenance phase. The patients in the active treatment arm of the study were maintained at either 24 mg/day or 32 mg/day at the discretion of the investigator.
Effects on the ADAS-cogFigure 10 illustrates the time course for the change from baseline in ADAS-cog scores for both dose groups over the 13 weeks of the study. At 13 weeks of treatment, the mean difference in the ADAS-cog change scores for the treated patients compared to the patients on placebo was 1.9. Galantamine hydrobromide at a dose of 24 to 32 mg/day was statistically significantly superior to placebo.
Figure 10: Time-Course of the Change From Baseline in ADAS-cog Score for Patients Completing 13 Weeks of Treatment
Figure 11 illustrates the cumulative percentages of patients from each of the two treatment groups who had attained at least the measure of improvement in ADAS-cog score shown on the X axis. Three change scores (10-point, 7-point and 4-point reductions) and no change in score from baseline have been identified for illustrative purposes, and the percent of patients in each group achieving that result is shown in the inset table.
The curves demonstrate that both patients assigned to Galantamine and placebo have a wide range of responses, but that the Galantamine group is more likely to show the greater improvement.
Figure 11: Cumulative Percentage of Patients Completing 13 Weeks of Double-Blind Treatment With Specified Changes From Baseline in ADAS-cog Scores. The Percentages of Randomized Patients Who Completed the Study Were: Placebo 90%, 24 to 32 mg/day 67%.
Change in ADAS-cog
| Treatment |
-10 |
-7 |
-4 |
0 |
| Placebo |
1.9% |
5.6% |
19.4% |
50.0% |
| 24 or 32 mg/day |
7.1% |
18.8% |
32.9% |
65.3% |
Effects on the CIBIC-plusFigure 12 is a histogram of the percentage distribution of CIBIC-plus scores attained by patients assigned to each of the two treatment groups who completed 13 weeks of treatment. The mean Galantamine-placebo differences for the group of patients in the mean rating of change from baseline were 0.37 units. The mean rating for the 24 to 32 mg/day group was statistically significantly superior to placebo.
Figure 12: Distribution of CIBIC-plus Ratings at Week 13
Age, Gender and Race
Patient's age, gender, or race did not predict clinical outcome of treatment.
Indications and Usage for Galantamine
Galantamine tablets are indicated for the treatment of mild to moderate dementia of the Alzheimer's type.
Contraindications
Galantamine tablets are contraindicated in patients with known hypersensitivity to Galantamine hydrobromide or to any excipients used in the formulation.
Warnings
Anesthesia
Galantamine, as a cholinesterase inhibitor, is likely to exaggerate the neuromuscular blocking effects of succinylcholine-type and similar neuromuscular blocking agents during anesthesia.
Cardiovascular Conditions
Because of their pharmacological action, cholinesterase inhibitors have vagotonic effects on the sinoatrial and atrioventricular nodes, leading to bradycardia and AV block. These actions may be particularly important to patients with supraventricular cardiac conduction disorders or to patients taking other drugs concomitantly that significantly slow heart rate. Post-marketing surveillance of marketed anticholinesterase inhibitors has shown, however, that bradycardia and all types of heart block have been reported in patients both with and without known underlying cardiac conduction abnormalities. Therefore all patients should be considered at risk for adverse effects on cardiac conduction.
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. The overall frequency of this event was 2% to 3% for Galantamine doses up to 24 mg/day compared with < 1% for placebo. No increased incidence of heart block was observed at the recommended doses.
Patients treated with Galantamine up to 24 mg/day using the recommended dosing schedule showed a dose related increase in risk of syncope (placebo 0.7% [2/286]; 4 mg BID 0.4% [3/692]; 8 mg BID 1.3% [7/552]; 12 mg BID 2.2% [6/273]).
Gastrointestinal Conditions
Through their primary action, cholinomimetics may be expected to increase gastric acid secretion due to increased cholinergic activity. Therefore, patients should be monitored closely for symptoms of active or occult gastrointestinal bleeding, especially those with an increased risk for developing ulcers, e.g., those with a history of ulcer disease or patients using concurrent nonsteroidal anti-inflammatory drugs (NSAIDS). Clinical studies of Galantamine hydrobromide have shown no increase, relative to placebo, in the incidence of either peptic ulcer disease or gastrointestinal bleeding.
Galantamine as a predictable consequence of its pharmacological properties, has been shown to produce nausea, vomiting, diarrhea, anorexia, and weight loss (see ADVERSE REACTIONS).
Genitourinary
Although this was not observed in clinical trials with Galantamine, cholinomimetics may cause bladder outflow obstruction.
Neurological Conditions
SeizuresCholinesterase inhibitors are believed to have some potential to cause generalized convulsions. However, seizure activity may also be a manifestation of Alzheimer's disease. In clinical trials, there was no increase in the incidence of convulsions with Galantamine compared to placebo.
Pulmonary Conditions
Because of its cholinomimetic action, Galantamine should be prescribed with care to patients with a history of severe asthma or obstructive pulmonary disease.
Precautions
Information for Patients and Caregivers
Caregivers should be instructed about the recommended dosage and administration of Galantamine tablets. Galantamine tablets should be administered twice per day, preferably with the morning and evening meals. Dose escalation (dose increases) should follow a minimum of 4 weeks at prior dose.
Patients and caregivers should be advised that the most frequent adverse events associated with use of the drug can be minimized by following the recommended dosage and administration.
Patients and caregivers should be advised to ensure adequate fluid intake during treatment. If therapy has been interrupted for several days or longer, the patient should be restarted at the lowest dose and the dose escalated to the current dose.
Death in Subjects with Mild Cognitive Impairment (MCI)
In two randomized placebo controlled trials of 2 years duration in subjects with mild cognitive impairment (MCI), a total of 13 subjects on Galantamine (n = 1,026) and one subject on placebo (n = 1,022) died. The deaths were due to various causes which could be expected in an elderly population; about half of the Galantamine deaths appeared to result from various vascular causes (myocardial infarction, stroke, and sudden death).
Although the difference in mortality between Galantamine and placebo-treated groups in these two studies was significant, the results are highly discrepant with other studies of Galantamine. Specifically, in these two MCI studies, the mortality rate in the placebo-treated subjects was markedly lower than the rate in placebo-treated patients in trials of Galantamine in Alzheimer's disease or other dementias (0.7 per 1,000 persons years compared to 22 to 61 per 1,000 person years, respectively). Although the mortality rate in the Galantamine-treated MCI subjects was also lower than that observed in Galantamine-treated patients in Alzheimer's disease and other dementia trials (10.2 per 1,000 person years compared to 23 to 31 per 1,000 person years, respectively), the relative difference was much less. When the Alzheimer's disease and other dementia studies were pooled (n = 6,000), the mortality rate in the placebo group numerically exceeded that in the Galantamine group. Furthermore, in the MCI studies, no subjects in the placebo group died after 6 months, a highly unexpected finding in this population.
Individuals with mild cognitive impairment demonstrate isolated memory greater than expected for their age and education, but do not meet current diagnostic criteria for Alzheimer's disease.
Special Populations
Hepatic ImpairmentIn patients with moderately impaired hepatic function, dose titration should proceed cautiously (see CLINICAL PHARMACOLOGY and DOSAGE AND ADMINISTRATION). The use of Galantamine in patients with severe hepatic impairment is not recommended.
Renal ImpairmentIn patients with moderately impaired renal function, dose titration should proceed cautiously (see CLINICAL PHARMACOLOGY and DOSAGE AND ADMINISTRATION). In patients with severely impaired renal function (CLcr < 9 mL/min) the use of Galantamine is not recommended.
Drug-Drug Interactions
(see also CLINICAL PHARMACOLOGY, Drug-Drug Interactions)
Use With AnticholinergicsGalantamine has the potential to interfere with the activity of anticholinergic medications.
Use With Cholinomimetics and Other Cholinesterase InhibitorsA synergistic effect is expected when cholinesterase inhibitors are given concurrently with succinylcholine, other cholinesterase inhibitors, similar neuromuscular blocking agents or cholinergic agonists such as bethanechol.
Effect of Other Drugs on Galantamine In vitro
CYP3A4 and CYP2D6 are the major enzymes involved in the metabolism of Galantamine. CYP3A4 mediates the formation of Galantamine-N-oxide; CYP2D6 leads to the formation of O-desmethylGalantamine. Because Galantamine is also glucuronidated and excreted unchanged, no single pathway appears predominant.
In vivo
Cimetidine and Ranitidine
Galantamine was administered as a single dose of 4 mg on day 2 of a 3-day treatment with either cimetidine (800 mg daily) or ranitidine (300 mg daily). Cimetidine increased the bioavailability of Galantamine by approximately 16%. Ranitidine had no effect on the PK of Galantamine.
Ketoconazole
Ketoconazole, a strong inhibitor of CYP3A4 and an inhibitor of CYP2D6, at a dose of 200 mg BID for 4 days, increased the AUC of Galantamine by 30%.
Erythromycin
Erythromycin, a moderate inhibitor of CYP3A4 at a dose of 500 mg QID for 4 days, affected the AUC of Galantamine minimally (10% increase).
Paroxetine
Paroxetine, a strong inhibitor of CYP2D6, at 20 mg/day for 16 days, increased the oral bioavailability of Galantamine by about 40%.
Memantine
Memantine, an N-methyl-D-aspartate receptor antagonist, at a dose of 10 mg BID, had no effect on the pharmacokinetics of Galantamine (16 mg/day) at steady-state.
Effect of Galantamine on Other Drugs In vitro
Galantamine did not inhibit the metabolic pathways catalyzed by CYP1A2, CYP2A6, CYP3A4, CYP4A, CYP2C, CYP2D6 or CYP2E1. This indicates that the inhibitory potential of Galantamine towards the major forms of cytochrome P450 is very low.
In vivo
Warfarin
Galantamine at 24 mg/day had no effect on the pharmacokinetics of R- and S-warfarin (25 mg single dose) or on the prothrombin time. The protein binding of warfarin was unaffected by Galantamine.
Digoxin
Galantamine at 24 mg/day had no effect on the steady-state pharmacokinetics of digoxin (0.375 mg once daily) when they were coadministered. In this study, however, one healthy subject was hospitalized for 2nd and 3rd degree heart block and bradycardia.
Carcinogenesis, Mutagenesis and Impairment of Fertility
In a 24-month oral carcinogenicity study in rats, a slight increase in endometrial adenocarcinomas was observed at 10 mg/kg/day (4 times the Maximum Recommended Human Dose [MRHD] on a mg/m2 basis or 6 times on an exposure [AUC] basis) and 30 mg/kg/day (12 times MRHD on a mg/m2 basis or 19 times on an AUC basis). No increase in neoplastic changes was observed in females at 2.5 mg/kg/day (equivalent to the MRHD on a mg/m2 basis or 2 times on an AUC basis) or in males up to the highest dose tested of 30 mg/kg/day (12 times the MRHD on a mg/m2 and AUC basis).
Galantamine was not carcinogenic in a 6-month oral carcinogenicity study in transgenic (P 53-deficient) mice up to 20 mg/kg/day, or in a 24-month oral carcinogenicity study in male and female mice up to 10 mg/kg/day (2 times the MRHD on a mg/m2 basis and equivalent on an AUC basis).
Galantamine produced no evidence of genotoxic potential when evaluated in the in vitro Ames S. typhimurium or E. coli reverse mutation assay, in vitro mouse lymphoma assay, in vivo micronucleus test in mice, or in vitro chromosome aberration assay in Chinese hamster ovary cells.
No impairment of fertility was seen in rats given up to 16 mg/kg/day (7 times the MRHD on a mg/m2 basis) for 14 days prior to mating in females and for 60 days prior to mating in males.
Pregnancy
Teratogenic Effects Pregnancy Category B
In a study in which rats were dosed from day 14 (females) or day 60 (males) prior to mating through the period of organogenesis, a slightly increased incidence of skeletal variations was observed at doses of 8 mg/kg/day (3 times the Maximum Recommended Human Dose [MRHD] on a mg/m2 basis) and 16 mg/kg/day. In a study in which pregnant rats were dosed from the beginning of organogenesis through day 21 postpartum, pup weights were decreased at 8 and 16 mg/kg/day, but no adverse effects on other postnatal developmental parameters were seen. The doses causing the above effects in rats produced slight maternal toxicity. No major malformations were caused in rats given up to 16 mg/kg/day. No drug related teratogenic effects were observed in rabbits given up to 40 mg/kg/day (32 times the MRHD on a mg/m2 basis) during the period of organogenesis.
There are no adequate and well controlled studies of Galantamine in pregnant women
