How long do you wait to admit patients after an overdose?

I know it depends on the medication and how much was taken, and how the patient appears clinically, etc., but as a general rule, what would you tell a referring hospital who wants to admit someone to your psychiatric unit after a significant overdose? For example, I received a call today about an adolescent who overdosed on 500 mg of a stimulant (either Ritalin or Adderall), and the referring ED wanted to admit him to our standalone psychiatric hospital 4 hours after the ingestion.... How long do you wait to admit patients after an overdose?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums