Underdosing of antiviral drugs, initial encounter

This diagnosis code indicates that a patient has taken less than the prescribed or recommended dose of an antiviral medication. This underdosing could lead to suboptimal treatment efficacy, viral resistance, or a worsening of the underlying viral infection.

This code is appropriate when a patient presents for initial evaluation or treatment of a condition resulting from or exacerbated by taking an insufficient amount of their antiviral medication. This includes situations where the patient admits to non-adherence, or when clinical evidence suggests inadequate drug levels due to underdosing.

• Always assign a secondary code for the specific viral infection being treated.
• Distinguish between underdosing (patient takes less than prescribed) and poisoning (patient takes incorrect substance or dose with harmful intent/effect).
• The 7th character "A" signifies an initial encounter, meaning the patient is receiving active treatment for the underdosing or its effects.