Hi there,
My family lived through an identical nightmare last fall. Our easy child swallowed 50 calcium channel blockers in a suicide attempt. We are very, very fortunate that he survived. He was dead for a few minutes but he was revived. He has made a dramatic and incredible recovery, though he still has cognitive impairments, and a physical disability to his leg.
Long term follow up psychiatric care is a must along with family counseling, assuming your child is a minor. You may also want to consider having him evaluated for an IEP if he didn't have one before this happened. In our case, stress about school was a major factor driving the attempt. And of course, there was (and remains) a tremendous amount of familial dysfunction.
Try to make sure he doesn't slide into his old ways. Don't let the conditions that led to the attempt continue to fester. Unfortunately we were not successful in eliciting any major change in our son's situation - though he did get an IEP and was placed in a special school for children with anxiety and depression, which is a big deal and hopefully will change the equation for him.
Best of luck - keep us posted.