Hi. The symptoms that you have mentioned indicate that your father is suffering from dementia. Regarding the medications, admenta which is memantine, is an anti dementia medication. It is one of the medicines which is started at the same dose prescribed by your doctor for dementia. Mirtazine which is used for anxiety and depression. Other two medications are multivitamins. Trust your doctor regarding the medications and be patient about the response. You should discuss any doubts regarding the treatment with him.
Next Steps
Start treatment and wait for response. Discuss any issues with the treating doctor.