Memantine dosing

The side effects of memantine are generally mild and include headache, dizziness, and constipation. Memantine is started at an initial dose of 5 mg each morning and is increased to 5 mg twice daily after 1 week. The maximum dose of memantine is 10 mg taken twice daily. A recent study indicates that memantine works syner-gistically with cholinesterase inhibitors (see Section 10.5.5), and it has quickly become routine clinical practice to coadminister memantine with one of these agents. 

Dosage The recommended starting dose of memantine is 5 mg once daily. The recommended target dose is 20 mg/day. Increase the dose in 5 mg increments to 10 mg/day (5 mg twice daily), 15 mg/day (5 mg and 10 mg as separate doses), and 20 mg/day (10 mg twice daily). The minimum recommended interval between dose increases is 1 week. 

Metabolism/Excretion- Memantine undergoes little metabolism, with the majority (57% to 82%) of an administered dose excreted unchanged in urine. Memantine has a terminal elimination half-life of about 60 to 80 hours. Renal clearance involves active tubular secretion. 

Renal function impairment Consider dose adjustment in patients with mild, moderate, and severe renal impairment. The use of memantine in patients with severe renal impairment is not recommended. 

Memantine (Namenda) [Anti Alzheimer Agent/NMDA Receptor Antagonist] Uses Mod/ evere Alzheimer Dz Action N-methyl-D-aspartate recqjtor antagonist Dose Target 20 mg/d, start 5 mg/d, t 5 mg/d to 20 mg/d, wait >1 wk before t dose use doses if >5mg/d Caution [B, /-] Hqjatic/mild-mod renal impair Disp Tabs, sol SE Dizziness Interactions t Effects W amantadine, carbonic anhydrase inhibitors, dextromethorphan, ketamine, Na bicarbonate t effects W/ any drug, herb, food that alkalinizes urine EMS Use NaHCOs w/ caution OD May cause restlessness, hallucinations, drowsiness, and fainting symptomatic and supportive... 

Memantine was approved by the FDA in October 2003 for the treatment of moderate to severe dementia of the Alzheimer s type. Its efficacy has been shown in placebo-controlled trials when taken as a monotherapy (Reisberg et al. 2003 Winblad and Poritis 1999) or in patients receiving stable donepezil therapy (Tariot et al. 2004). It is currently available in 5- and 10-mg tablets, and doses can be administered with or without meals. 

Memantine is weU absorbed after oral administration, is not highly protein bound, and has a half-life of 60-80 hours. Memantine is primarily renahy excreted unchanged in the urine however, a portion of the administered dose is converted to three inactive metabolites. The cytochrome P450 system does not play a key role in its metabolism (Namenda 2005). 

Sang C. N., Booher S., Gilron I., Parada S., and Max M. B. (2002). Dextromethorphan and memantine in painful diabetic neuropathy and postherpetic neuralgia efficacy and dose-response trials. Anesthesiology 96 1053-1061. 

Beister A, Kraus P, Kuhn W, Dose M, Weindl A, Gerlach M (2004) The N-methyl-D-aspartate antagonist memantine retards progression of Huntington s disease. J Neural Transm Suppl 117-122. 

DOPAMINERGICS AMANTADINE t CNS side-effects Additive effects Monitor more closely for confusion, gastrointestinal side-effects. Initiate therapy with bupropion at the lowest dose and t gradually. Manufacturers recommend avoiding co-administration of amantadine and memantine... 

Both the patient and the patient s caregiver should be instructed on howto dose memantine since patients themselves have moderate to severe dementia and may require assistance... 

Beister A, Kr aus P, Kulirr W, Dose M, Weindl A, Geriach M (2004) Tire N-metliyl-D-asparfate antagonist memantine retar ds progr es-sion of Himdng ton s disease. J Neiu al Transm Suppl 68 117—122. 

Memantine is likely to be used as monotherapy and also in combination with cholinesterase inhibitors, particularly in patients with moderate to severe AD. Memantine should be initiated at 5 mg once a day and increased weekly by 5 mg a day to the effective dose of 10 mg twice daily. It may be given with or without food. Dosing of 10 mg daily is recommended in patients with creatinine clearance of 40 to 60 mL/min and patients with severe renal impairment (creatinine clearance <40 mL/min) should not receive memantine. ... 

Memantine is a colorless to white crystalline substmice readily soluble in water. Its oral bioavailability is nearly 1(X)%. Memantine readily crosses the blood-brain barrier, and while in organism ii shows linear, dose-proportional pharmacokinetics and weak protein-binding properties. 

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