Donepezil Hydrochloride

Pronunciation

Donepezil hydrochloride 10mg (ARICEPT 10mg)

Donepezil hydrochloride 5mg (ARICEPT 5mg)

Introduction

Donepezil hydrochloride, is a reversible inhibitor of acetylcholinesterase. It is used for the treatment of mild to moderate dementia in Alzheimer’s disease.

Generic Name 藥名	HA Code 藥物代碼	Classification藥物分類
Donepezil HCL Tablet 5mg	DONE01	P1S1S3
Donepezil HCL Tablet 10mg	DONE02	P1S1S3
Donepezil HCL Orodispersible Tablet 5mg	DONE03	P1S1S3

Mechanism of Action

Acetylcholinesterase inhibiting drug

Dosage

By Oral: initially 5 mg once daily at bedtime, increased if necessary, after one month to max. 10 mg daily.

Clinical benefit should be assessed on a regular basis. Up to half the patients will show a slower rate of cognitive decline. Donepezil should be discontinued in those not responding.

Side Effects

Common side effects include

• Nausea and vomiting
• difficulty sleeping
• aggression
• Loss of appetite
• Diarrhoea
• Feeling tired
• Muscle cramps

These effects usually last 1 – 3 weeks and then lessen

Serious side effects may include:

• Abnormal heart rhythms
• Difficulty emptying urine from the bladder
• seizures

Donepezil, like other acetylcholinesterase inhibitors, can cause nightmares due to enhanced activation of the visual association cortex during REM sleep. Taking donepezil in the morning can reduce the frequency of nightmares.

Pharmacokinetics

Oral bioavailability	Donepezil hydrochloride is readily absorbed from the gastrointestinal tract with a relative oral bioavailability of 100%. It is about 95% bound to plasma proteins, mainly albumin.
Onset of action	Peak plasma levels in 3-4 hours
Elimination half-life	70 hours, but around 100 hours in elderly
Duration of action	With daily dosing, steady-state concentration is reached within 3 weeks after initiation of therapy. Once at steady-state, plasma donepezil hydrochloride concentrations show little variability over the course of the day.

How long does it take for donepezil to take effect?

Donepezil may take as long as 12 weeks to begin working.

What time of day should donepezil be taken?

It is usually taken once a day with or without food, just before bedtime. Take donepezil at around the same time every day.

Why is donepezil taken at night?

Donepezil is taken at night because it can cause irregular or slow heartbeat for some patients, which can cause fainting. When it is taken at bedtime, affected patients will be able to sleep through those side effects.

Drug Management

Monitoring

• acetylcholinesterase inhibitor may increase gastric acid secretion, so patients should be monitored closely for GI bleeding, especially those receiving concurrent NSAID drugs.
• check body weight regularly
• monitor the cognitive, global functions, and ADL activities
• monitor the sleeping quality

Drug interaction

Drugs given with gabapentin	Potential Effect
Antacids (containing Magnesium with aluminium)	Absorption of gabapentin from the gut is reduced by antacids. It is recommended that gabapentin is taken at least 2 hours after any such antacid.
Morphine	Morphine reduces the clearance of gabapentin; patients receiving both drugs should be monitored for signs for CNS depression and doses should be reduced accordingly.