Legal prescription or not it is up to the officer at the scene to determine if you were impaired at the time of the accident. In most cases I have reviewed in the last 5 years in New Jersey the charge stuck. A more desirable deal can be reckless driving which carriers the same revocation time 6 months first offense, but without the DUI surcharges and court ordered counseling. I do agree you need an attorney that is an ex prosecutor with an ex LEO as the investigator also having a medical expert that used to work in the state forensic lab is a huge plus. Most importantly no priors on your part. Now like a previous poster said if you killed or severly injured someone that is a different story, course you'll still need the above dream team. Also if you are driving a commercial vehicle there is usaually a mandatory drug test as mandated by the USDOT.
Take care. Billylll