Adverse effect of histamine H2-receptor blockers, init

This code signifies an undesirable or harmful reaction experienced by a patient due to the therapeutic use of a histamine H2-receptor blocker, such as cimetidine, ranitidine, or famotidine. These adverse effects occur despite the drug being correctly prescribed and administered.

Apply this code when a patient presents for initial treatment of symptoms directly attributable to an adverse reaction from an H2-receptor blocker. This includes reactions like headache, dizziness, diarrhea, or more severe effects such as confusion or gynecomastia, when the patient is first seen for this specific issue.

• Always assign an additional code for the specific manifestation of the adverse effect (e.g., R51 for headache).
• Ensure documentation clearly states the drug was prescribed and taken correctly, distinguishing it from poisoning or underdosing.
• The "A" in the 7th character indicates an initial encounter for the adverse effect, meaning the patient is receiving active treatment for the condition.