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All about: Donepezil

Big Image Pronouncation: (doh-NEP-e-zil)
Class: Cholinesterase inhibitor

Trade Names:
Aricept
- Tablets 5 mg
- Tablets 10 mg
- Tablets, orally disintegrating 5 mg
- Tablets, orally disintegrating 10 mg

Mechanism of Action

Pharmacology

Increases acetylcholine by inhibiting acetylcholinesterase, thereby increasing cholinergic function.

Pharmacokinetics

Absorption

Bioavailability is 100%. T max is 3 to 4 h.

Distribution

Vd is 12 L/kg (at steady state). Approximately 96% protein bound (75% to albumin and 21% alpha-1 acid glycoprotein)

Metabolism

Metabolized by CYP2D6 and 3A4, and undergoes glucuronidation to 4 major metabolites (2 active) and several minor metabolites.

Elimination

The t ½ is approximately 70 h. Cl is 0.13 L/h/kg. Approximately 57% recovered in urine and 15% in feces; approximately 17% of dose recovered unchanged in urine.

Special Populations

Hepatic Function Impairment

Cl decreased 20% in patients with stable alcoholic cirrhosis.

Indications and Usage

Treatment of mild to severe dementia of the Alzheimer type.

Contraindications

Hypersensitivity to donepezil or piperidine derivatives.

Dosage and Administration

Mild to Moderate Alzheimer Disease
Adults

PO 5 mg once daily; may increase to 10 mg once daily after 4 to 6 wk, depending on prescriber and patient preference.

Severe Alzheimer Disease
Adults

PO Start with 5 mg once daily. Increase to 10 mg once daily after 4 to 6 wk.

General Advice

  • Orally disintegrating tablets are bioequivalent to tablets.
  • Administer in the evening, just prior to bedtime.
  • May be taken without respect to food.
  • Allow the oral disintegrating tablet to dissolve on the tongue and follow with water.

Storage/Stability

Store at 59° to 86°F.

Drug Interactions

Anticholinergic drugs

Possible reduction of anticholinergic effects.

Cholinesterase inhibitors/cholinomimetics

Synergistic effects may occur.

CYP2D6 and CYP3A4 inducers (eg, carbamazepine, dexamethasone, phenobarbital, phenytoin, rifampin)

May increase donepezil rate of elimination.

CYP2D6 and CYP3A4 inhibitors (eg, ketoconazole, quinidine)

May inhibit donepezil metabolism.

Succinylcholine

Muscle relaxation may be exaggerated.

Laboratory Test Interactions

None well documented.

Adverse Reactions

The 10 mg dose, with 1-wk titration, is likely to be associated with a higher incidence of cholinergic adverse reactions than the 5 mg dose. With 6-wk titration, the frequency of these same adverse reactions was similar between 5 and 10 mg dosing. The following adverse reactions are based on 6-wk titration.

Cardiovascular

Hypertension (3%); hemorrhage, syncope (2%); abnormal ECG, atrial fibrillation, bradycardia, heart failure, hot flashes, hypertension, hypotension, vasodilation (at least 1%); heart block (postmarketing).

CNS

Headache (10%); insomnia (9%); dizziness (8%); fatigue, nervousness (5%); abnormal dreams, depression, hallucinations, hostility (3%); confusion, emotional lability, personality disorder, somnolence (2%); abnormal crying, abnormal gait, aggression, agitation, anxiety, aphasia, asthenia, ataxia, convulsions, delusions, increased libido, irritability, paresthesia, restlessness, tremor, vertigo, wandering (at least 1%); hallucinations, neuroleptic malignant syndrome (postmarketing).

Dermatologic

Eczema (3%); diaphoresis, pruritus, skin rash, ulcer, urticaria (at least 1%).

EENT

Blurred vision, cataract, eye irritation, pharyngitis, sore throat (at least 1%).

GI

Nausea (11%); diarrhea (10%); anorexia, vomiting (8%); abdominal pain, bloating, constipation, dyspepsia, fecal incontinence, gastroenteritis, GI bleeding, epigastric pain (at least 1%); pancreatitis (postmarketing).

Genitourinary

Frequent urination, urinary incontinence (2%); cystitis, glucosuria, hematuria, nocturia, UTI (at least 1%).

Hepatic

Cholecystitis, hepatitis (postmarketing).

Hematologic-Lymphatic

Ecchymosis (5%); anemia (at least 1%); hemolytic anemia (postmarketing).

Metabolic-Nutritional

Increased CPK, weight decrease (3%); dehydration, hyperlipemia (2%); edema, increased alkaline phosphatase and LDH, peripheral edema (at least 1%); hyponatremia (postmarketing).

Musculoskeletal

Muscle cramps (6%); back pain (3%); arthritis (2%); bone fracture (at least 1%).

Respiratory

Bronchitis, dyspnea, increased cough, pneumonia (at least 1%).

Miscellaneous

Accident (13%); pain (9%); chest pain, fever (2%); flu syndrome, fungal pain, toothache (at least 1%).

Precautions

Monitor

Evaluate patient's mental status, cognitive function, and activities of daily living prior to initiation of therapy and periodically thereafter during prolonged treatment. Monitor for signs and symptoms of GI bleed.


Pregnancy

Category C .

Lactation

Undetermined.

Children

Safety and efficacy not established.

CV effects

May have vagotonic effects on the sinoatrial and AV nodes.

Concomitant medical conditions

Increases cholinergic activity and, therefore, can affect other organ systems, possibly leading to bradycardia, bladder outflow obstruction, increased gastric acid secretion, generalized convulsions, or bronchoconstriction. Use drug with caution in patients susceptible to these reactions.

Overdosage

Symptoms

Cholinergic crisis (eg, bradycardia, collapse, convulsions, hypotension, muscle weakness, respiratory depression, salivation, severe nausea, sweating, vomiting).

Patient Information

  • Advise patient or caregiver that this drug does not alter the Alzheimer process and that the effectiveness of the medication may lessen in time.
  • Instruct patient or caregiver to continue using other medications for dementia as prescribed by health care provider.
  • Advise patient to take prescribed dose once daily in the evening just before bedtime.
  • Advise patient that donepezil can be taken without regard to meals but to take with food if stomach upset occurs.
  • Advise patient receiving orally disintegrating tablet to allow tablet to dissolve on tongue and then follow with water.
  • Advise patient that if a dose is missed to skip that dose and take next dose at regularly scheduled time. Caution patient not to double the dose to catch up.
  • Advise patient or caregiver not to discontinue drug or change dose unless advised by health care provider.
  • Caution patient or caregiver not to increase the dose of donepezil if Alzheimer symptoms worsen or do not appear to be improving, but to notify health care provider.
  • Advise patient or caregiver that diarrhea, nausea, and vomiting commonly occur, especially during the early phase of treatment with donepezil, but that these symptoms will usually go away within 1 to 3 wk with continued therapy.
  • Advise patient to notify health care provider if any of the following occur: appetite loss; depression; fainting; persistent nausea, diarrhea, or vomiting; sleeplessness; or any other unexplained change or symptoms.
  • Caution patient that donepezil may cause drowsiness or dizziness, and to use caution while driving or performing other activities requiring mental alertness or coordination until tolerance is determined.

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