As I am sure you already know, dysnomia
is a learning disability
where you have difficulty in retrieving a word from memory. All of us have this to an extent. At some time or the other, we have experienced the tip-of-the-tongue phenomenon where we are sure we know the word but just cannot retrieve it at that time. In dysnomia, this kind of difficulty is more pervasive and persistent.
A skilled speech therapist can certainly help you in dealing with this problem. You will also benefit by practising to use synonyms and descriptions when you cannot retrieve the exact words. There isn't much evidence for the use of medications to treat dysnomia when it occurs as a learning disability. I suggest you meet a speech therapist and take it up from there.
Dr. Saifuddin Kharawala