👤 By the CinnaRN Clinical Content Team🕐 Updated 2026-08-23🏷️ Pharmacological Therapies🔖 Free to read, print, and share
Also known as: INH · isoniazid · TB medication · tuberculosis drug
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Use this quick-reference guide to spot, treat, and prevent Isoniazid on the NCLEX. Keep it handy during review and on exam day!
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📒 The 1-minute cheat sheet
📌 Use
TB treatment + prophylaxis (INH)
Long course → months
📌 Toxic
Hepatotoxic → monitor LFTs
Peripheral neuropathy (↓B6)
✅ Do
Give pyridoxine (B6) → prevents neuropathy
Empty stomach, NO alcohol
🚩 Report
Jaundice, dark urine, RUQ pain
Numbness, tingling extremities
📚 Isoniazid — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what must be reported, and what to teach.
Isoniazid is a first-line drug for treating and preventing tuberculosis, often given for 6 to 9 months. Its major risks are hepatotoxicity and peripheral neuropathy, the latter prevented by vitamin B6. The key principle is monitoring liver function and giving pyridoxine to prevent nerve damage.
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Key points
Understand these first
Isoniazid is bactericidal against Mycobacterium tuberculosis and is a cornerstone of TB therapy.
Hepatotoxicity is the most serious adverse effect, and risk rises with age and alcohol use.
Peripheral neuropathy is prevented by giving pyridoxine (vitamin B6).
It is taken on an empty stomach, 1 hour before or 2 hours after meals, for best absorption.
It interacts with tyramine- and histamine-containing foods (aged cheese, red wine, certain fish) and can cause a reaction, and it raises phenytoin levels.
Adherence for the full course is essential to prevent drug-resistant TB.
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Nursing priorities
What to do, in order
Administer pyridoxine (vitamin B6) as prescribed to prevent peripheral neuropathy.
Monitor liver function tests and assess for signs of hepatotoxicity.
Give on an empty stomach and assess for numbness or tingling.
Stress strict adherence for the entire course to prevent resistance.
Assess and counsel the patient to avoid alcohol during therapy.
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Red flags — report now
Escalate immediately
Jaundice, dark urine, nausea, fatigue, or right upper quadrant pain may signal hepatotoxicity - hold the drug and report.
Numbness or tingling in the hands and feet should be reported.
Avoid alcohol entirely because it greatly increases liver injury risk.
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Labs & values
Numbers to know
AST 10-40 units/L (baseline and periodic monitoring)
ALT 7-56 units/L (hold drug if markedly elevated)
Bilirubin 0.3-1.0 mg/dL (monitor for hepatotoxicity)
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Patient teaching
What patients must know
Take vitamin B6 as prescribed to protect your nerves.
Avoid all alcohol while on this medication.
Take on an empty stomach and avoid aged cheeses, smoked fish, and certain wines.
Report yellow skin or eyes, dark urine, fatigue, or numbness and tingling, and keep all follow-up appointments.
❓ Isoniazid: NCLEX FAQs
What are the priority nursing interventions for Isoniazid?
Administer pyridoxine (vitamin B6) as prescribed to prevent peripheral neuropathy. Monitor liver function tests and assess for signs of hepatotoxicity. Give on an empty stomach and assess for numbness or tingling. Stress strict adherence for the entire course to prevent resistance.
What are the warning signs of Isoniazid a nurse must report?
Jaundice, dark urine, nausea, fatigue, or right upper quadrant pain may signal hepatotoxicity - hold the drug and report. Numbness or tingling in the hands and feet should be reported. Avoid alcohol entirely because it greatly increases liver injury risk.
What do I need to know about Isoniazid for the NCLEX?
Isoniazid is bactericidal against Mycobacterium tuberculosis and is a cornerstone of TB therapy. Hepatotoxicity is the most serious adverse effect, and risk rises with age and alcohol use. Peripheral neuropathy is prevented by giving pyridoxine (vitamin B6). It is taken on an empty stomach, 1 hour before or 2 hours after meals, for best absorption.
What patient teaching is important for Isoniazid?
Take vitamin B6 as prescribed to protect your nerves. Avoid all alcohol while on this medication. Take on an empty stomach and avoid aged cheeses, smoked fish, and certain wines. Report yellow skin or eyes, dark urine, fatigue, or numbness and tingling, and keep all follow-up appointments.
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Quick Tip
Isoniazid is bactericidal against Mycobacterium tuberculosis and is a cornerstone of TB therapy.