Risk factors for an accidental heroin overdose:
(1) loss of tolerance during a period of abstinence (unable to metabolize the same dose as when tolerant)
(2) using drug with a higher purity
(3) misjudged dose (due to intoxication, poor eyesight, etc.)
(4) novice user
(5) taking a medication that interferes with heroin metabolism
A person who is likely to have a loss of tolerance:
(1) newly released prisoner
(2) weekend user
Interpreting a blood level of heroin can be difficult because of tolerance. A patient who has developed a high level of tolerance may survive a dose that would be lethal to a person lacking tolerance.
Differential diagnosis:
(1) suicide (intentional overdose)
(2) homicide
(3) toxicity from non-heroin adulterant
(4) overdose from alcohol or another drug being abused
