On page 78, the report mentions how those convicted of drugs related offences (particularly if the offence amounts to trafficking) will be considered the most "dangerous" of prisoners, which affects where they will be sent to prison.
Citation: Notes verbales from the Permanent Mission of Spain to the United Nations Office: Remarks of the Government of Spain on the report of the Special Rapporteur on torture, (2004) E/CN.4/2004/G/19