Which circumstance would preclude treatment with isoniazid (INH)?

Which circumstance would preclude treatment with isoniazid (INH)?

• A. Active TB infection with HIV
• B. An alcoholic who has hepatitis C (HCV)
• C. Diabetes mellitus
• D. Chronic kidney disease

Answer: (B)

Isoniazid can cause serious liver injury, so its use is avoided when there is preexisting liver disease or significant liver function impairment. In someone who is an alcoholic and has hepatitis C, the liver is already damaged, and adding isoniazid greatly increases the risk of severe hepatitis or liver failure. That combination makes INH unsafe to use, which is why this circumstance would preclude treatment with INH. It's worth noting that HIV infection alone is not an automatic reason to withhold INH, though its management requires attention to drug interactions and liver function. Diabetes mellitus and chronic kidney disease do not by themselves rule out INH use, though monitoring remains important.

Isoniazid can cause serious liver injury, so its use is avoided when there is preexisting liver disease or significant liver function impairment. In someone who is an alcoholic and has hepatitis C, the liver is already damaged, and adding isoniazid greatly increases the risk of severe hepatitis or liver failure. That combination makes INH unsafe to use, which is why this circumstance would preclude treatment with INH.

It's worth noting that HIV infection alone is not an automatic reason to withhold INH, though its management requires attention to drug interactions and liver function. Diabetes mellitus and chronic kidney disease do not by themselves rule out INH use, though monitoring remains important.