our neurologist said since mt hubby had been on namenda for 21/2 yrs it was no longer helping and he should be weaned off this upset me but did as Dr recommended What a mistaken. After being weaned off for three days we have been living a nightmare. Finally got Dr to call in Rx and started him back on namenda three days ago. Does anyone know how long it takes for namenda to be effective after being off of it totally for 3 days?