Galantamine

Introduction

Galantamine Hydrobromide, is a reversible inhibitor of acetylcholinesterase. It also has an intrinsic action on nicotinic receptors. 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
Galantamine HBR Prolonged Release Cap 8mg	GALA04	P1S1S3
Galantamine HBR Prolonged Release Cap 16mg	GALA05	P1S1S3
Galantamine HBR Prolonged Release Cap 24mg	GALA06	P1S1S3

Mechanism of Action

Acetylcholinesterase inhibiting drug

Dosage

By Oral: initially 4 mg twice daily for 4 weeks increased to 8 mg twice daily for 4 weeks; maintenance 8-12 mg twice daily according to response and tolerance.

A modified-release preparation is also available for once-daily use. Clinical benefit should be assessed on a regular basis.

Reductions in dose may be necessary in patients with hepatic or renal impairment.

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

Pharmacokinetics

Oral bioavailability	Donepezil hydrochloride is rapidly and well absorbed from the gastrointestinal tract with an oral bioavailability of about 90%. Plasma protein binding is about 18%.
Onset of action	Peak plasma levels in about one hour after ingestion from immediate-release preparations; 4 to 5 hours after a dose of modified-release formulations
Metabolism	Partially metabolized by CYP2D6, CYP3A4
Elimination half-life	7 to 8 hours

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: Hepatic metabolism of donepezil via the cytochrome P450 will be affected by drugs that inhibit the isoenzyme CYP3A4 and CYP2D6 Interactions do not generally apply to steroid used for topical action including inhalation, unless specified.

Drugs given with donepezil	Potential Effect
CYP2D6 inhibitors: SSRI, such as Paroxetine quinidine	May increase plasma-donepezil concentration, increasing the risk of severe adverse reactions.
May increase plasma-donepezil concentration, increasing the risk of severe adverse reactions.	May increase plasma-donepezil concentration, increasing the risk of severe adverse reactions
CYP3A4 inducers & CYP2D6 inducers: Rifampicin Phenytoin Carbamazepine	May reduce plasma-donepezil concentration