Poisoning by histamine H2-receptor blockers, undet, subs

This code signifies a poisoning event involving histamine H2-receptor blockers where the intent (e.g., accidental, intentional self-harm, assault) cannot be determined. The patient is receiving active treatment for the poisoning or experiencing residual effects during an encounter following the initial treatment. H2-receptor blockers are medications commonly used to reduce stomach acid production.

This code is appropriate for follow-up encounters where a patient is being managed for the effects of an H2-receptor blocker overdose or adverse reaction, and the circumstances surrounding the poisoning remain unclear. Examples include patients returning for monitoring of kidney function after an acute overdose, or those presenting with persistent neurological symptoms attributed to the poisoning.

• Always assign an additional code for the specific H2-receptor blocker if known (e.g., ranitidine, cimetidine).
• Ensure documentation clearly states that the intent of the poisoning is undetermined.
• Verify that the encounter is indeed "subsequent" and not the initial treatment for the poisoning.