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Difficulty: HardMonitoring and Treatment Evaluation

A 42-year-old man comes to the clinic for initiation of pharmacotherapy for recently diagnosed active pulmonary tuberculosis. Sputum acid-fast bacilli smears were positive, and nucleic acid amplification testing confirmed Mycobacterium tuberculosis. He has a history of type 2 diabetes mellitus but is otherwise healthy. A standard four-drug regimen consisting of isoniazid, rifampin, pyrazinamide, and ethambutol is planned. Which of the following baseline evaluations MUST be documented prior to starting and monitored during this specific regimen? (Select all that apply)

  1. Hepatic aminotransferases and bilirubinAnswer
  2. Visual acuity and color discrimination testingAnswer
  3. C
    High-frequency audiometry
  4. D
    Electrocardiography with QTc interval measurement
  5. E
    Thyroid-stimulating hormone level

Answer

The required evaluations are hepatic aminotransferases and bilirubin, as well as visual acuity and color discrimination testing.
The standard four-drug regimen for active tuberculosis includes isoniazid, rifampin, pyrazinamide, and ethambutol. Three of these agents (isoniazid, rifampin, and pyrazinamide) are potentially hepatotoxic, necessitating a baseline hepatic panel (aminotransferases, bilirubin, and alkaline phosphatase) and ongoing symptom-driven or periodic monitoring. Ethambutol can cause dose-dependent optic neuritis, which typically presents as diminished visual acuity and loss of red-green color discrimination; therefore, baseline visual acuity (e.g., Snellen chart) and color discrimination (e.g., Ishihara plates) testing are mandatory prior to initiation.

Step-by-Step Solution

1
Identify the specific medications comprising the planned standard four-drug regimen for active tuberculosis.
The regimen consists of isoniazid, rifampin, pyrazinamide, and ethambutol (RIPE therapy).
Different anti-tuberculosis medications have distinct toxicity profiles requiring highly specific monitoring parameters.
2
Determine the primary toxicities for each of the identified first-line agents.
Isoniazid, rifampin, and pyrazinamide are all known to be hepatotoxic. Ethambutol is uniquely associated with dose-dependent retrobulbar optic neuritis.
Baseline parameters must map directly to the expected high-risk toxicities of the prescribed pharmacotherapy.
3
Select the appropriate corresponding baseline and ongoing monitoring tests while excluding tests meant for alternative or second-line agents.
Hepatic panel (aminotransferases and bilirubin) and ophthalmologic testing (visual acuity and color discrimination) are selected. Audiometry, electrocardiography, and thyroid testing are excluded as they monitor toxicities of streptomycin, bedaquiline/fluoroquinolones, and ethionamide, respectively.
Over-ordering tests (such as audiometry for a patient not taking an aminoglycoside) represents inappropriate healthcare utilization and poor test sequencing.

Key Concept

Monitoring parameters for high-risk pharmacotherapies (First-line Anti-Tuberculosis Regimen)
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Topics

Monitoring and Treatment Evaluation

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