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Pharmacology · chapter 7 · Anti-infective Drugs

Introduction to Tuberculosis and Antitubercular Drugs

The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.

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Key points

  1. What latent TB can wait for

    Latent TB can reside in the person’s lungs for years, waiting to activate either spontaneously or through an episode of immunosuppression that can be brought on by conditions such as HIV, diabetes, end-stage kidney disease, or the use of corticosteroids (e.g., dexamethasone, prednisone).

  2. Typical signs of TB

    Individuals with TB typically present with common signs and symptoms, including weight loss, fatigue, productive cough, fever, and night sweats. Other signs and symptoms may include chest pain and hemoptysis (coughing up of blood).

  3. Chest x-ray, then sputum

    The health care provider should order a chest x-ray and then sputum samples if the x-ray shows infiltrates suggestive of TB.

  4. Reading the skin test

    Skin testing introduces tuberculin protein under the skin; redness and swelling (induration) at the injection site due to the presence of TB antibodies indicates latent TB infection.

  5. At least six months of therapy

    Due to the difficulty of drug penetration and the slow-growing nature of the organism, TB treatment requires at least 6 months of therapy. Failure to adhere to TB therapy can lead to clinical worsening in the client and more resistant strains of M. tuberculosis.

  6. The standard four-drug regimen

    Traditionally, clients with an active TB infection begin therapy with a four-drug regimen consisting of isoniazid, rifampin, pyrazinamide, and ethambutol for 2 months followed by 4 additional months of isoniazid and rifampin.

  7. Directly observed therapy

    One way to help ensure adherence is by using directly observed therapy, in which a trained observer watches the client take every dose of their TB medication.

  8. Ethambutol and vision

    The major adverse effects seen with ethambutol are optic nerve inflammation, changes in visual acuity, and loss of ability to distinguish between the colors red and green.

  9. Isoniazid and the liver

    Isoniazid is a known hepatotoxin; serial liver function tests should be performed to determine whether therapy should be altered.

  10. Isoniazid neurotoxicity

    Isoniazid also can cause neurotoxicity, including peripheral neuropathies at standard doses and seizures and coma in overdose. Clients particularly at risk for neurotoxicity include those who are pyridoxine deficient (e.g., pregnant clients, individuals with excessive alcohol intake).

  11. Pyrazinamide: liver and uric acid

    Pyrazinamide also is a known hepatotoxin, so serial liver function tests should be monitored for evidence of liver injury. In addition, pyrazinamide raises uric acid levels.

  12. Rifampin speeds up other drugs

    These drugs can prove a challenging addition to a client’s medication regimen because induction of CYP3A4 can speed the metabolism of affected drugs and lead to therapeutic failure.

  13. Orange-red body fluids

    Rifampin can cause the client’s secretions (e.g., urine, tears, sweat) to turn an orange to red color, which clients should be warned about before they start therapy.

  14. Signs of liver impairment to report

    Tell the client to report signs and symptoms of liver impairment (e.g., yellowish skin, vomiting, abdominal pain, dark urine) that may occur while clients are taking isoniazid, rifampin, or pyrazinamide.

Terms to know

latent TB
After an individual inhales aerosol droplets containing M. tuberculosis, they may either clear the organism immediately, develop an active TB infection, or develop latent TB, in which the organism goes into a dormant state.
hemoptysis
Other signs and symptoms may include chest pain and hemoptysis (coughing up of blood).
directly observed therapy
One way to help ensure adherence is by using directly observed therapy, in which a trained observer watches the client take every dose of their TB medication.

Practice questions

Stuck on select-all-that-apply? How to take them one option at a time.

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Every question here, with the answer

  1. A client started rifampin for active tuberculosis two days ago and calls the clinic, worried that their urine and sweat have turned orange-red. What is the nurse's best response?

    1. This means the dose is too high; take half of it.
    2. This is an expected effect of rifampin and is not a reason to stop the drug.
    3. This is a sign of kidney failure; you need a urine test today.
    4. Stop the rifampin and go to the emergency department.

    Answer: This is an expected effect of rifampin and is not a reason to stop the drug.

    Rifampin can turn urine, tears and sweat orange to red, and clients should be warned about this before therapy. Stopping the drug, treating it as kidney failure or halving the dose are not supported and would disrupt a regimen that must be taken every dose.

  2. A client taking ethambutol, isoniazid, rifampin and pyrazinamide reports that red and green now look alike. Which drug is the most likely cause?

    1. Pyrazinamide
    2. Isoniazid
    3. Rifampin
    4. Ethambutol

    Answer: Ethambutol

    The major adverse effects of ethambutol are optic nerve inflammation, changes in visual acuity and loss of red-green color discrimination, so the client should report visual changes. Isoniazid is linked to liver injury and neuropathy, rifampin to drug interactions and orange secretions, and pyrazinamide to liver injury and raised uric acid.

  3. A client on isoniazid reports new numbness and tingling in both feet. The nurse recognises this as which adverse effect?

    1. Hepatotoxicity
    2. Peripheral neuropathy
    3. Optic nerve inflammation
    4. Raised uric acid

    Answer: Peripheral neuropathy

    Isoniazid can cause neurotoxicity, including peripheral neuropathies at standard doses, and clients should report numbness or tingling in the extremities. Hepatotoxicity shows as yellow skin, dark urine or abdominal pain; optic neuritis is linked to ethambutol and raised uric acid to pyrazinamide.

  4. A nurse is teaching a client who is starting isoniazid, rifampin and pyrazinamide. Which signs should the client report because they may mean liver impairment? Select all that apply.

    1. Dark urine
    2. Vomiting
    3. Abdominal pain
    4. Orange-colored tears
    5. Yellowish skin

    Answer: Dark urine, Vomiting, Abdominal pain, Yellowish skin

    Yellowish skin, vomiting, abdominal pain and dark urine are the listed signs of liver impairment with isoniazid, rifampin or pyrazinamide. Orange-red tears are an expected, harmless effect of rifampin.

  5. A client is being discharged on a standard regimen for active tuberculosis. Which statements by the client show correct understanding? Select all that apply.

    1. Treatment usually lasts about two weeks.
    2. If I miss a dose, I will take it when I remember but will not double up.
    3. I need to take every dose so the TB does not become resistant.
    4. I should avoid excessive alcohol while I take these drugs.
    5. I can stop the pills once my cough goes away.

    Answer: If I miss a dose, I will take it when I remember but will not double up., I need to take every dose so the TB does not become resistant., I should avoid excessive alcohol while I take these drugs.

    Every dose must be taken to ensure success, reduce resistance and prevent transmission; excessive alcohol raises the risk of liver injury; and a missed dose is taken when remembered without doubling. Stopping when symptoms improve risks resistance, and TB treatment requires at least 6 months.

  6. A client who takes several other medications is starting rifampin. Which nursing action is most important before the first dose?

    1. Screen the medication list for interactions and alert the health care provider as needed.
    2. Check the client's red-green color vision.
    3. Give pyridoxine to prevent orange urine.
    4. Measure the client's uric acid level.

    Answer: Screen the medication list for interactions and alert the health care provider as needed.

    Rifampin is a potent CYP3A4 inducer that can speed the metabolism of other drugs and cause therapeutic failure, so the nurse screens for interactions. Color vision relates to ethambutol, uric acid to pyrazinamide, and pyridoxine is not a treatment for orange urine.

Where every quote comes from

Section 7.5 Introduction to Tuberculosis and Antitubercular Drugs of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.

The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.