1. N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluoropropoxy) benzylamine or a pharmaceutically acceptable salt for use in the treatment of Alzheimer's disease by increasing or enhancing the effect of an acetylcholinesterase inhibitor comprising administering an effective daily dose of said compound to a patient in need of such treatment, where the effective daily dose administered to the patient is from about 30 mg to about 60 mg. 2. N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluoropropoxy) benzylamine or a pharmaceutically acceptable salt for use in the treatment of Alzheimer's disease as an additional therapy for treatment with an acetylcholinesterase inhibitor comprising administering an effective daily dose of N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluoropropoxy) benzylamine or a pharmaceutically acceptable salt to the needy such treatment to a patient where the effective daily dose administered to the patient is from about 30 mg to about 60 mg. 3. N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluoropropoxy) benzylamine according to claim 1 or 2, wherein the pharmaceutically acceptable salt is hydrochloride. . N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluoropropoxy) benzylamine according to claim 1 or 2, wherein the dose is administered as a composition with immediate effect release. 5. N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluoropropoxy) benzylamine according to claim 1 or 2 for the treatment of Alzheimer's disease with mild severity to moderate. 6. N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluorogfopoxy) benzylamine according to claim 1 or 2, wherein donepezil is an acetylcholinesterase inhibitor. 7. N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluoropropoxy) benzylamine according to claim 1 or 2, wherein the acetylcholinesterase inhibitor is rivastigmine. 8. N- (2- (6-fluoro-1H-indol-3-yl) ethyl) -3- (2,2,3,3-tetrafluoropropoxy) benzylamine ac
