memantine hydrochloride 10 MG Oral Tablet [Namenda]

INDICATIONS AND USAGE Memantine hydrochloride extended-release capsules are indicated for the treatment of moderate to severe dementia of the Alzheimer’s type. Memantine hydrochloride extended-release capsules are an N-methyl-D-aspartate (NMDA) receptor antagonist indicated for the treatment of moderate to severe dementia of the Alzheimer’s type. ( 1 )

DOSAGE AND ADMINISTRATION The recommended starting dose of memantine hydrochloride extended-release capsules is 7 mg once daily; the dose should be increased in 7 mg increments to the recommended maintenance dose of 28 mg once daily; the minimum recommended interval between dose increases is one week. ( 2.1 ) Patients with severe renal impairment: the recommended maintenance dose of memantine hydrochloride extended-release capsules is 14 mg once daily. ( 2.3 ) 2.1 Recommended Dosing The dosage of memantine hydrochloride extended-release capsules shown to be effective in a controlled clinical trial is 28 mg once daily. The recommended starting dose of memantine hydrochloride extended-release capsules is 7 mg once daily. The dose should be increased in 7 mg increments to the recommended maintenance dose of 28 mg once daily. The minimum recommended interval between dose increases is one week. The dose should only be increased if the previous dose has been well tolerated. The maximum recommended dose is 28 mg once daily. Memantine hydrochloride extended-release capsules can be taken with or without food. Memantine hydrochloride extended-release capsules can be taken intact or may be opened, sprinkled on applesauce, and thereby swallowed. The entire contents of each memantine hydrochloride extended-release capsule should be consumed; the dose should not be divided. Except when opened and sprinkled on applesauce, as described above, memantine hydrochloride extended-release capsules should be swallowed whole. Memantine hydrochloride extended-release capsules should not be divided, chewed, or crushed. If a patient misses a single dose of memantine hydrochloride extended-release capsules, that patient should not double up on the next dose. The next dose should be taken as scheduled. If a patient fails to take memantine hydrochloride extended-release capsules for several days, dosing may need to be resumed at lower doses and retitrated as described above. 2.2 Switching from Memantine Hydrochloride Tablets to Memantine Hydrochloride Extended-Release Capsules Patients treated with memantine hydrochloride tablets may be switched to memantine hydrochloride extended-release capsules as follows: It is recommended that a patient who is on a regimen of 10 mg twice daily of memantine hydrochloride tablets be switched to memantine hydrochloride extended-release capsules 28 mg once daily capsules the day following the last dose of 10 mg memantine hydrochloride tablets. There is no study addressing the comparative efficacy of these 2 regimens. In a patient with severe renal impairment, it is recommended that a patient who is on a regimen of 5 mg twice daily of memantine hydrochloride tablets be switched to memantine hydrochloride extended-release capsules 14 mg once daily capsules the day following the last dose of 5 mg memantine hydrochloride tablets. 2.3 Dosing in Patients with Renal Impairment In patients with severe renal impairment (creatinine clearance of 5 to 29 mL/min, based on the Cockcroft-Gault equation), the recommended maintenance dose (and maximum recommended dose) is 14 mg/day [see Clinical Pharmacology ( 12.3 )] .

WARNINGS AND PRECAUTIONS Conditions that raise urine pH may decrease the urinary elimination of memantine, resulting in increased plasma levels of memantine. ( 5.1 , 7.1 ) 5.1 Genitourinary Conditions Conditions that raise urine pH may decrease the urinary elimination of memantine resulting in increased plasma levels of memantine [see Drug Interactions ( 7.1 )] . 5.1 Genitourinary Conditions Conditions that raise urine pH may decrease the urinary elimination of memantine resulting in increased plasma levels of memantine [see Drug Interactions ( 7.1 )] .

CONTRAINDICATIONS Memantine hydrochloride extended-release capsules are contraindicated in patients with known hypersensitivity to memantine hydrochloride or to any excipients used in the formulation . •Memantine hydrochloride extended-release capsules are contraindicated in patients with known hypersensitivity to memantine hydrochloride or to any excipients used in the formulation.( 4 )

CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Persistent activation of central nervous system N-methyl-D-aspartate (NMDA) receptors by the excitatory amino acid glutamate has been hypothesized to contribute to the symptomatology of Alzheimer’s disease. Memantine is postulated to exert its therapeutic effect through its action as a low to moderate affinity uncompetitive (open-channel) NMDA receptor antagonist which binds preferentially to the NMDA receptor-operated cation channels. There is no evidence that memantine prevents or slows neurodegeneration in patients with Alzheimer’s disease. 12.2 Pharmacodynamics Memantine showed low to negligible affinity for GABA, benzodiazepine, dopamine, adrenergic, histamine and glycine receptors and for voltage-dependent Ca 2+ , Na + or K + channels. Memantine also showed antagonistic effects at the 5HT3 receptor with a potency similar to that for the NMDA receptor and blocked nicotinic acetylcholine receptors with one-sixth to one-tenth the potency. I n vitro studies have shown that memantine does not affect the reversible inhibition of acetylcholinesterase by donepezil, galantamine, or tacrine. 12.3 Pharmacokinetics Absorption Following oral administration memantine is highly absorbed with peak concentrations reached in about 3 to 7 hours. Memantine has linear pharmacokinetics over the therapeutic dose range. Food has no effect on the absorption of memantine. Distribution The mean volume of distribution of memantine is 9 to 11 L/kg and the plasma protein binding is low (45%). Metabolism Memantine undergoes partial hepatic metabolism. The hepatic microsomal CYP450 enzyme system does not play a significant role in the metabolism of memantine. Elimination Memantine is excreted predominantly (about 48%) unchanged in urine and has a terminal elimination half- life of about 60 to 80 hours. The remainder is converted primarily to three polar metabolites which possess minimal NMDA receptor antagonistic activity: the N-glucuronide conjugate, 6-hydroxy memantine, and 1-nitroso­ deaminated memantine. A total of 74% of the administered dose is excreted as the sum of the parent drug and the N-glucuronide conjugate. Renal clearance involves active tubular secretion moderated by pH dependent tubular reabsorption. Pharmacokinetics in Specific Populations Gender Following multiple dose administration of memantine hydrochloride 20 mg daily, females had about 45% higher exposure than males, but there was no difference in exposure when body weight was taken into account. Elderly The pharmacokinetics of memantine hydrochloride in young and elderly subjects are similar. Renal Impairment Memantine pharmacokinetics were evaluated following single oral administration of 20 mg memantine hydrochloride in 8 subjects with mild renal impairment (creatinine clearance, CLcr, >50 to 80 mL/min), 8 subjects with moderate renal impairment (CLcr 30 to 49 mL/min), 7 subjects with severe renal impairment (CLcr 5 to 29 mL/min) and 8 healthy subjects (CLcr > 80 mL/min) matched as closely as possible by age, weight and gender to the subjects with renal impairment. Mean AUC 0- ∞ increased by 4%, 60%, and 115% in subjects with mild, moderate, and severe renal impairment, respectively, compared to healthy subjects. The terminal elimination half-life increased by 18%, 41%, and 95% in subjects with mild, moderate, and severe renal impairment, respectively, compared to healthy subjects. No dosage adjustment is recommended for patients with mild and moderate renal impairment. Dosage should be reduced in patients with severe renal impairment [see Dosage and Administration ( 2 )] . Hepatic Impairment Memantine pharmacokinetics were evaluated following the administration of single oral doses of 20 mg in 8 subjects with moderate hepatic impairment (Child-Pugh Class B, score 7 to 9) and 8 subjects who were age-, gender-, and weight-matched to the hepatically-impaired subjects. There was no change in memantine exposure (based on C max and AUC) in subjects with moderate hepatic impairment as compared with healthy subjects. However, terminal elimination half-life increased by about 16% in subjects with moderate hepatic impairment as compared with healthy subjects. No dose adjustment is recommended for patients with mild and moderate hepatic impairment. Memantine should be administered with caution to patients with severe hepatic impairment as the pharmacokinetics of memantine have not been evaluated in that population. Drug-Drug Interactions Use with Cholinesterase Inhibitors Coadministration of memantine with the AChE inhibitor donepezil hydrochloride did not affect the pharmacokinetics of either compound. Furthermore, memantine did not affect AChE inhibition by donepezil. In a 24-week controlled clinical study in patients with moderate to severe Alzheimer’s disease, the adverse event profile observed with a combination of memantine hydrochloride and donepezil was similar to that of donepezil alone. Effect of Memantine on the Metabolism of Other Drugs I n vitro studies conducted with marker substrates of CYP450 enzymes (CYP1A2, -2A6, -2C9, ­2D6, -2E1, -3A4) showed minimal inhibition of these enzymes by memantine. In addition, in vitro studies indicate that at concentrations exceeding those associated with efficacy, memantine does not induce the cytochrome P450 isozymes CYP1A2, -2C9, -2E1 and -3A4/5. No pharmacokinetic interactions with drugs metabolized by these enzymes are expected. Pharmacokinetic studies evaluated the potential of memantine for interaction with warfarin, and buproprion. Memantine did not affect the pharmacokinetics of the CYP2B6 substrate buproprion or its metabolite hydroxy-buproprion. Furthermore, memantine did not affect the pharmacokinetics or pharmacodynamics of warfarin as assessed by the prothrombin INR. Effect of Other Drugs on Memantine Memantine is predominantly renally eliminated, and drugs that are substrates and/or inhibitors of the CYP450 system are not expected to alter the metabolism of memantine. Drugs Eliminated via Renal Mechanisms Because memantine is eliminated in part by tubular secretion, coadministration of drugs that use the same renal cationic system, including hydrochlorothiazide (HCTZ), triamterene (TA), metformin, cimetidine, ranitidine, quinidine, and nicotine, could potentially result in altered plasma levels of both agents. However, coadministration of memantine and HCTZ/TA did not affect the bioavailability of either memantine or TA, and the bioavailability of HCTZ decreased by 20%. In addition, coadministration of memantine with the antihyperglycemic drug Glucovance ® (glyburide and metformin hydrochloride) did not affect the pharmacokinetics of memantine, metformin and glyburide. Furthermore, memantine did not modify the serum glucose lowering effect of Glucovance ® , indicating the absence of a pharmacodynamic interaction. Drugs Highly Bound to Plasma Proteins Because the plasma protein binding of memantine is low (45%), an interaction with drugs that are highly bound to plasma proteins, such as warfarin and digoxin, is unlikely.