So I Had A Patient That Overdosed On 60mg Of

So I had a patient that overdosed on 60mg of MS Contin and 30 tabs of MSIR 5mg. This happen Monday morning but he still was not breathing well and was receiving Narcan IV Push. My question is how do you know what to start a Narcan drip at and when should the person being taken off in case he goes through withdrawal of his chronic use of Morphine