Each film-coated tablet contains: Donepezil Hydrochloride, USP 5 mg and 10 mg.
Pharmacology: Pharmacodynamics: Current theories on the pathogenesis of the cognitive signs and symptoms of Alzheimer's disease attribute some of them to a deficiency of cholinergic neurotransmission.
Donepezil hydrochloride 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 acetylcholinesterase. There is no evidence that donepezil alters the course of the underlying dementing process.
Pharmacokinetics: Pharmacokinetics of donepezil are linear over a dose range of 1 to 10 mg given once daily. The rate and extent of absorption of donepezil hydrochloride tablets are not influenced by food.
Donepezil hydrochloride ODT 5 mg and 10 mg are bioequivalent to donepezil hydrochloride 5 mg and 10 mg tablets, respectively. The elimination half-life of donepezil is about 70 hours, and the mean apparent plasma clearance (Cl/F) is 0.13 to 0.19 L/hr/kg. Following multiple dose administration, donepezil accumulates in plasma by 4 to 7 folds, and steady state is reached within 15 days. The steady state volume of distribution is 12 to 16 L/kg. Donepezil is approximately 96% bound to human plasma proteins, mainly to albumins (about 75%) and alpha1 - acid glycoprotein (about 21%) over the concentration range of 2 to 1000 ng/mL. Donepezil is both excreted in the urine intact and extensively metabolized to four major metabolites, two of which are known to be active, and a number of minor metabolites, not all of which have been identified. Donepezil is metabolized by CYP 450 isoenzymes 2D6 and 3A4 and undergoes glucuronidation. Following administration of C-labeled donepezil, plasma radioactivity, expressed as a percent of the administered dose, was present primarily as intact donepezil (53%) and as 6-O-desmethyl donepezil (11%), which has been reported to inhibit AChE to the same extent as donepezil in vitro and was found in plasma at concentrations equal to about 20% of donepezil. Approximately 57% and 15% of the total radioactivity was recovered in urine and feces, respectively, over a period of 10 days, while 28% remained unrecovered, with about 17% of the donepezil dose recovered in the urine as unchanged drug. Examination of the effect of CYP2D6 genotype in Alzheimer's patients showed differences in clearance values among CYP2D6 genotype subgroups. When compared to the extensive metabolizers, poor metabolizers had a 31.5% slower clearance and ultra-rapid metabolizers had a 24% faster clearance.
Hepatic Disease: In a study of 10 patients with stable alcoholic cirrhosis, the clearance of donepezil hydrochloride was decreased by 20% relative to 10 healthy age- and sex-matched subjects.
Renal Disease: In a study of 11 patients with moderate to severe renal impairment (Cl <18 mL/min/1.73 m2) the clearance of donepezil hydrochloride did not differ from 11 age- and sex-matched healthy subjects.
Age: No formal pharmacokinetic study was conducted to examine age-related differences in the pharmacokinetics of donepezil hydrochloride. Population pharmacokinetic analysis suggested that the clearance of donepezil in patients decreases with increasing age. When compared with 65-year old, subjects, 90-year old subjects have a 17% decrease in clearance, while 40-year old subjects have a 33% increase in clearance. The effect of age on donepezil clearance may not be clinically significant.
Gender and Race: No specific pharmacokinetic study was conducted to investigate the effects of gender and race on the disposition of donepezil hydrochloride. However, retrospective pharmacokinetic analysis and population pharmacokinetic analysis of plasma donepezil concentrations measured in patients with Alzheimer's disease indicates that gender and race (Japanese and Caucasians) did not affect the clearance of donepezil hydrochloride to an important degree.
Body weight: There was a relationship noted between body weight and clearance. Over the range of body weight from 50 kg to 110 kg, clearance increased from 7.77 L/hr to 14.04 L/hr, with a value of 10 L/hr for 70 kg individuals.
Donepezil hydrochloride is indicated for the treatment of dementia of the Alzheimer's type. Efficacy has been demonstrated inpatients with mild, moderate, and severe Alzheimer's disease.
Donepezil hydrochloride tablets can be taken with or without food.
Mild to Moderate Alzheimer's Disease: The recommended starting dosage of donepezil hydrochloride tablets is 5 mg administered once per day in the evening, just prior to retiring. The maximum recommended dosage of donepezil hydrochloride in patients with mild to moderate Alzheimer's disease is 10 mg per day. A dose of 10 mg should not be administered until patients have been on a daily dose of 5 mg for 4 to 6 weeks.
Moderate to Severe Alzheimer's Disease: The recommended starting dosage of donepezil hydrochloride tablets is 5 mg administered once per day in the evening, just prior to retiring. A dose of 10 mg should not be administered until patients have been on a daily dose of 5 mg for 4 to 6 weeks.
Renal and hepatic impairment: A similar dose schedule can be followed for patients with renal impairment, as clearance of donepezil hydrochloride is not affected by this condition.
Due to possible increased exposure in mild to moderate hepatic impairment, dose escalation should be performed according to individual tolerability. There are no data for patients with severe hepatic impairment.
Children: Donepezil hydrochloride is not recommended for use in children.
Because strategies for the management of overdose are continually evolving, it is advisable to contact a Poison Control Center to determine the latest recommendations for the management of an overdose of any drug.
The estimated median lethal dose of donepezil hydrochloride following administration of a single oral dose in mice and rats is 45 and 32 mg/kg, respectively, or approximately 225 and 160 times the maximum recommended human dose of 10 mg per day. Dose-related signs of cholinergic stimulation were observed in animals and included reduce spontaneous movement, prone position, staggering gait, lacrimation, clonic convulsions, depressed respiration, salivation, miosis, tremors, fasciculation and lower body surface temperature.
Overdosage with cholinesterase inhibitors can result in cholinergic crisis characterized by severe nausea, vomiting, salivation, sweating, bradycardia, hypotension, respiratory depression, collapse and convulsions. Increasing muscle weakness is a possibility and may result in death if respiratory muscles are involved.
As in any case of overdose, general supportive measures should be utilized. Tertiary anticholinergics such as atropine may be used as an antidote for Donepezil overdosage. Intravenous atropine sulphate titrated to effect is recommended: an initial dose of 1.0 to 2.0 mg IV with subsequent doses based upon clinical response. Atypical responses in blood pressure and heart rate have been reported with other cholinomimetics when co-administered with quaternary anticholinergics such as glycopyrrolate. It is not known whether donepezil hydrochloride and/or its metabolites can be removed by dialysis (hemodialysis, peritoneal dialysis, or hemofiltration).
Donepezil Hydrochloride is contraindicated to the following: Patients with gastrointestinal or urinary tract obstruction, it is not recommended in patients recovering from bladder or gastrointestinal surgery.
Patients with a known hypersensitivity to donepezil hydrochloride, piperidine derivatives, or to any excipients used in the formulation.
It is contraindicated in pregnancy.
Anesthesia: Donepezil Hydrochloride, as a cholinesterase inhibitor, is likely to exaggerate succinylcholine-type muscle relaxation during anesthesia.
Cardiovascular Conditions: Because of their pharmacological action, cholinesterase inhibitors may have vagotonic effects on heart rate (e.g., bradycardia). The potential for this action may be particularly important to patients with "sick sinus syndrome" or other supraventricular cardiac conduction conditions, such as sinoatrial or atrioventricular block.
There have been reports of syncope and seizures. In investigating such patients, the possibility of heart block or long sinusal pauses should be considered.
Nausea and Vomiting: Donepezil hydrochloride tablets, as a predictable consequence of their pharmacological properties, have been shown to produce diarrhea, nausea, and vomiting. These effects, when they occur, appear more frequently with the 10 mg/day dose than with the 5 mg/day dose.
Although in most cases, these effects have been transient, sometimes lasting one to three weeks, and have resolved during continued use of donepezil hydrochloride tablets, patients should be observed closely at the initiation of treatment and after dose increases.
Peptic Ulcer Disease and GI Bleeding: Through their primary action, cholinesterase inhibitors 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 at increased risk for developing ulcers, e.g., those with a history of ulcer disease or those receiving concurrent nonsteroidal anti-inflammatory drugs (NSAIDs). Clinical studies of donepezil hydrochloride tablets in a dose of 5 mg/day to 10 mg/day have shown no increase, relative to placebo, in the incidence of either peptic ulcer disease or gastrointestinal bleeding.
Genitourinary: Although not observed in clinical trials of Donepezil Hydrochloride, cholinomimetics may cause bladder outflow obstruction.
Neurological Conditions: Seizures: Cholinomimetics are believed to have some potential to cause generalized convulsions. However, seizure activity may also be a manifestation of Alzheimer's disease.
Cholinomimetics may have the potential to exacerbate or induce extra pyramidal symptoms.
Pulmonary Conditions: Because of their cholinomimetic actions, cholinesterase inhibitors should be prescribed with care to patients with a history of asthma or obstructive pulmonary disease.
The administration of Donepezil concomitantly with other inhibitors of acetylcholinesterase, agonists or antagonists of the cholinergic system should be avoided.
Severe Hepatic Impairment: There are no data for patients with severe hepatic impairment.
Use in Children: The safety and effectiveness of donepezil hydrochloride tablets in children have not been established.
Pregnancy: Pregnancy Category C. There are no adequate or well-controlled studies in pregnant women. Donepezil hydrochloride tablets should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Oral administration of donepezil to pregnant rats and rabbits during the period of organogenesis did not produce any teratogenic effects at doses up to 16 mg/kg/day (approximately 16 times the maximum recommended human dose [MRHD] of 10 mg/day on a mg/m basis) and 10 mg/kg/day (approximately 20 times the MRHD on a mg/m basis), respectively. Oral administration of donepezil (1, 3, 10 mg/kg/day) to rats during late gestation and throughout lactation to weaning produced an increase in still births and reduced offspring survival through postpartum day 4 at the highest dose. The no-effect dose of 3 mg/kg/day is approximately 3 times the MRHD on a mg/m basis.
Nursing Mothers: It is not known whether donepezil is excreted in human milk. Caution should be exercised when donepezil hydrochloride tablets are administered to a nursing woman.
The most common adverse events are diarrhea, muscle cramps, fatigue, nausea, vomiting and insomnia.
Adverse reactions reported as more than an isolated case are listed as follows, by system organ class and by frequency. Frequencies are defined as: common (>1/100, <1/10), uncommon (>1/1,000, <1/100) and rare (>1/10,000, <1/1,000). (See table.)
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Effect of Donepezil Hydrochloride Tablets on the Metabolism of Other Drugs: No in vivo clinical trials have investigated the effect of donepezil hydrochloride tablets on the clearance of drugs metabolized by CYP 3A4 (e.g. cisapride, terfenadine) or by CYP 2D6 (e.g. imipramine). However, in vitro studies show a low rate of binding to these enzymes (mean K about 50 to 130 μM), that, given the therapeutic plasma concentrations of donepezil (164 nM), indicates little likelihood of interference. Based on in vitro studies, donepezil shows little or no evidence of direct inhibition of CYP2B6, CYP2C8 and CYP2C19 at clinically relevant concentrations.
Whether donepezil hydrochloride tablets have any potential for enzyme induction is not known. Formal pharmacokinetic studies evaluated the potential of donepezil hydrochloride tablets for interaction with theophylline, cimetidine, warfarin, digoxin and ketoconazole. No effects of donepezil hydrochloride tablets on the pharmacokinetics of these drugs were observed.
Effect of Other Drugs on the Metabolism of Donepezil Hydrochloride Tablets: Ketoconazole and quinidine, strong inhibitors of CYP450 3A and 2D6, respectively, inhibit donepezil metabolism in vitro. Whether there is a clinical effect of quinidine is not known.
Population pharmacokinetic analysis showed that in the presence of concomitant CYP2D6 inhibitors donepezil AUC was increased by approximately 17% to 20% in Alzheimer's disease patients taking donepezil hydrochloride tablets 10 mg. This represented an average effect of weak, moderate, and strong CYP2D6 inhibitors. In a 7-day crossover study in 18 healthy volunteers, ketoconazole (200 mg q.d.) increased mean donepezil (5 mg q.d.) concentrations (AUC0 to 24 and Cmax) by 36%. The clinical relevance of this increase in concentration is unknown.
Inducers of CYP 3A (e.g., phenytoin, carbamazepine, dexamethasone, rifampin, and phenobarbital) could increase the rate of elimination of donepezil hydrochloride tablets. Formal pharmacokinetic studies demonstrated that the metabolism of donepezil hydrochloride tablets is not significantly affected by concurrent administration of digoxin or cimetidine.
An in vitro study showed that donepezil was not a substrate of P-glycoprotein.
Drugs Highly Bound to Plasma Proteins: Drug displacement studies have been performed in vitro between this highly bound drug (96%) and other drugs such as furosemide, digoxin, and warfarin. Donepezil hydrochloride at concentrations of 0.3 to 10 micrograms/mL did not affect the binding of furosemide (5 micrograms/mL), digoxin (2 ng/mL), and warfarin (3 micrograms/mL) to human albumin. Similarly, the binding of donepezil hydrochloride to human albumin was not affected by furosemide, digoxin and warfarin.
Store at temperatures not exceeding 30°C.
N06DA02 - donepezil ; Belongs to the class of anticholinesterases. Used in the management of dementia.
Torpezil 10 FC tab 10 mg
100's (P6,920/box)
Torpezil 5 FC tab 5 mg
100's (P5,420/box)
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