Home Drug Guide Isoniazid, Pyrazinamide, Rifampin

Drug Guide

Generic Name

Isoniazid, Pyrazinamide, Rifampin

Brand Names Rifater

Classification

Therapeutic: Antitubercular agents

Pharmacological: Combination antimycobacterial agents

FDA Approved Indications

  • Latent tuberculosis infection and active tuberculosis

Mechanism of Action

Isoniazid inhibits Mycobacterium tuberculosis synthesis of mycolic acids, essential components of the bacterial cell wall. Pyrazinamide disrupts membrane transport and energy production in the bacteria. Rifampin inhibits DNA-dependent RNA polymerase in bacteria, suppressing RNA synthesis.

Dosage and Administration

Adult: As per TB treatment guidelines, typically once daily or twice weekly, depending on regimen; specific dosages depend on weight and disease severity.

Pediatric: Dosing based on weight, typically 10-20 mg/kg for Isoniazid, 25-35 mg/kg for Pyrazinamide, and 10 mg/kg for Rifampin.

Geriatric: Use with caution; monitor for hepatic function, as risk of hepatotoxicity increases.

Renal Impairment: Adjustments may be necessary, especially for Pyrazinamide.

Hepatic Impairment: Use cautiously; monitor liver function regularly.

Pharmacokinetics

Absorption: Well absorbed orally

Distribution: Wide distribution, including cerebrospinal fluid (CSF) especially with meningeal inflammation

Metabolism: Isoniazid mainly hepatic; Rifampin hepatic; Pyrazinamide hepatic and renal

Excretion: Urine primarily; Rifampin also excreted in bile

Half Life: Isoniazid: 1-4 hours; Rifampin: 3-5 hours; Pyrazinamide: 9-10 hours

Contraindications

  • History of hypersensitivity to any of the components

Precautions

  • Hepatic impairment, alcohol use, pre-existing liver disease; monitor liver enzymes regularly.

Adverse Reactions - Common

  • Hepatotoxicity (Uncommon but serious, can be severe)
  • Peripheral neuropathy (more with Isoniazid) (Common)
  • Gastrointestinal discomfort (Common)
  • Rash (Uncommon)

Adverse Reactions - Serious

  • Disseminated or fulminant hepatitis (Rare)
  • Optic neuritis (with high doses of Isoniazid) (Rare)
  • Allergic reactions such as rash, eosinophilia (Uncommon)

Drug-Drug Interactions

  • Alcohol (increases hepatotoxicity risk), other hepatotoxic drugs, oral contraceptives (may decrease efficacy)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor liver function tests, complete blood counts, and for signs of hepatotoxicity; assess for symptoms of peripheral neuropathy.

Diagnoses:

  • Impaired skin integrity related to hypersensitivity reactions
  • Risk for hepatotoxicity

Implementation: Administer as prescribed; monitor for adverse effects; provide pyridoxine (vitamin B6) to prevent peripheral neuropathy with Isoniazid.

Evaluation: Lack of adverse effects; resolution of TB symptoms; normal liver function tests.

Patient/Family Teaching

  • Take medications exactly as prescribed.
  • Report symptoms of liver problems (fatigue, weakness, nausea, jaundice).
  • Avoid alcohol and hepatotoxic drugs.
  • Complete entire course of therapy to prevent resistance.

Special Considerations

Black Box Warnings:

  • Hepatotoxicity, especially in older adults and those with pre-existing liver disease

Genetic Factors: Slow acetylators of Isoniazid may have increased risk of toxicity.

Lab Test Interference: False-positive urine scans for opiates with Rifampin.

Overdose Management

Signs/Symptoms: Hepatic failure, hypersensitivity, neurotoxicity with Isoniazid overdose.

Treatment: Supportive care, activated charcoal if recent ingestion, monitor liver function, pyridoxine (vitamin B6) for Isoniazid overdose.

Storage and Handling

Storage: Store at room temperature, away from moisture and light.

Stability: Stable under proper storage conditions.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.