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Community data Updated 2 months ago

Memantine Hydrochloride

Drugs for Dementia Prescription
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Indications

Alzheimer's Disease

Dementa XR is used to treat all forms of dementia caused by Alzheimer's disease. It may also be prescribed for other types of dementia.

⚠️ Always consult a registered physician before taking any medicine.

Pharmacology

Persistent activation of N-methyl-D-aspartate (NMDA) receptors in the Central Nervous System by the excitatory amino acid glutamate has been thought to contribute to the symptoms of Alzheimer's disease. Memantine is believed to work as a low to moderate affinity, uncompetitive (open-channel) NMDA receptor antagonist. It binds preferentially to the NMDA receptor-operated cation channels.

Memantine is well absorbed after it is taken by mouth, and its pharmacokinetics stay linear across the therapeutic dose range. Most of it leaves the body unchanged in the urine, and its terminal elimination half-life is about 60-80 hours. After an oral dose, Memantine is highly absorbed and peak concentrations are reached in about 3-7 hours. Food has no effect on how well Memantine is absorbed. The mean volume of distribution of Memantine is 9-11 L/kg, and its plasma protein binding is low (45%).

Memantine is only partly metabolised in the liver. About 48% of the administered drug is excreted unchanged in the urine. The rest is converted mainly into three polar metabolites, which have minimal NMDA receptor antagonistic activity: the N-glucuronide conjugate, 6-hydroxy Memantine and 1-nitroso-deaminated Memantine. In total, 74% of the administered dose is excreted as the parent drug plus the N-glucuronide conjugate. The hepatic microsomal CYP-450 enzyme system does not play a significant role in the metabolism of Memantine.

Pregnancy & Breastfeeding

Pregnancy Category B. That said, there haven't been adequate, well-controlled studies of Memantine in pregnant women, so it should only be used during pregnancy if the potential benefit is thought to outweigh the potential risk to the unborn baby. Whether Memantine passes into human breast milk isn't known, but since many drugs do, it should be used with caution in breastfeeding mothers.

⚠️ Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.

Dosage Reference

⚠️ Reference ranges from official sources only. Consult your doctor for personalized dosing.

Adults: For adults and older patients, the recommended maintenance dose of Memantine is 20 mg every day. To lower the risk of side effects, this dose should be reached through gradual upward titration, increasing by 5 mg per week over three weeks, so that the maintenance dose of 20 mg per day is reached from the start of week 4, following this dosage guideline. In week 1, the dose everyday is 5 mg (1 tablet) in the morning and no dose at night. In week 2, the dose everyday is 5 mg (1 tablet) in the morning and 5 mg (1 tablet) at night. In week 3, the dose everyday is 10 mg (2 tablets) in the morning and 5 mg (1 tablet) at night. From week 4 onwards, the dose everyday is 10 mg (2 tablets) in the morning and 10 mg (2 tablets) at night. If a dose is missed, simply wait and take the next dose at the usual time. Do not double the dose to make up for the missed one. In patients with moderate renal impairment, meaning a creatinine clearance of 30 to 49 ml per minute, the daily dose should be 10 mg, equivalent to 1 ml of solution or two downward strokes. If this is well tolerated after at least 7 days of treatment, the dose may be increased up to 20 mg per day according to the standard titration scheme described above. In patients with severe renal impairment, meaning a creatinine clearance of 5 to 29 ml per minute, the daily dose should be 10 mg, equivalent to 1 ml of solution or two downward strokes, per day. In patients with mild or moderate hepatic impairment, no dosage adjustment is needed. Memantine is not recommended for patients with severe hepatic impairment. Memantine is not recommended for children under 18 years of age, as there is not enough data on its safety and efficacy in this age group.

Side Effects & Interactions

Side Effects

No side-effect data recorded yet.