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Chapter 41
Antitubercular Drugs
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Antitubercular Drugs
Tuberculosis (TB)
Caused by Mycobacterium tuberculosis
Antitubercular drugs treat all forms of Mycobacterium
TB is most commonly characterized by granulomas  in the lungs  
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3. Mycobacterium Infections
Common infection sites
Lung (primary site)
Brain
Bone
Liver
Kidney
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4. Mycobacterium Infections (cont’d)
Aerobic bacillus
Passed from infected:
Humans
Cows (bovine) and birds (avian)
Much less common
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5. Mycobacterium Infections (cont’d)
Tubercle bacilli are conveyed by droplets
Droplets are expelled by coughing or sneezing, and they then gain entry into the body by inhalation
Tubercle bacilli then spread to other body organs via blood and lymphatic systems
Tubercle bacilli may become dormant, or walled off by calcified or fibrous tissue
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Antitubercular Drugs
First-line drugs
isoniazid (INH)*
rifapentine
ethambutol
rifabutin
pyrazinamide (PZA)
rifampin
streptomycin
*Primary drug used
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7. Antitubercular Drugs (cont’d)
Second-line drugs
capreomycin
amikacin
cycloserine
levofloxacin
ethionamide
ofloxacin
kanamycin
para-aminosalicyclic acid (PAS)
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8. Tuberculosis-Related Injections
Purified protein derivative (PPD)
A diagnostic injection given intradermally in doses of 5 tuberculin units (0.1 mL) to detect exposure to the tuberculosis (TB) organism
Bacille Calmette-Guérin (BCG)
A vaccine injection derived from an inactivated strain of Mycobacterium bovis
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9. Antitubercular Drug Therapy Considerations
Perform drug-susceptibility testing on the first Mycobacterium spp. that is isolated from a patient specimen to prevent the development of multidrug-resistant TB (MDR-TB)
Even before the results of susceptibility tests are known, begin a regimen with multiple antitubercular drugs (to reduce chances of development of resistance)
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10. Classroom Response Question
A patient with tuberculosis has been taking antitubercular drugs. A sputum culture is ordered to test for acid-fast bacilli. When is the best time for the nurse to obtain the sputum culture?
In the morning
Noon
Five o’clock in the evening
Ten o’clock in the evening
Correct answer: A
Rationale: If the prescriber has ordered collection of a sputum specimen to test for acid-fast bacilli, it is best to obtain the sample early in the morning. The most common order is for three consecutive morning specimens, with a repeat specimen several weeks later.
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11. Antitubercular Drug Therapy Considerations (cont’d)
Adjust drug regimen once the results of susceptibility testing are known
Monitor patient compliance closely during therapy
Problems with successful therapy occur because of patient nonadherence to drug therapy and the increased incidence of drug-resistant organisms
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Mechanism of Action
Three groups
Protein wall synthesis inhibitors: streptomycin, kanamycin, capreomycin, rifampin, rifabutin, others
Cell wall synthesis inhibitors: cycloserine, ethionamide, INH
Other mechanisms of action: ethambutol, INH, PAS, ethionamide
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13. Antitubercular Therapy
Effectiveness depends on:
Type of infection
Adequate dosing
Sufficient duration of treatment
Adherence to drug regimen
Selection of an effective drug combination
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14. Antitubercular Therapy (cont’d)
Problems
Drug-resistant organisms
Drug toxicity
Patient nonadherence
MDR-TB
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Isoniazid (INH)
Drug of choice for TB
Resistant strains of Mycobacterium emerging
Metabolized in the liver through acetylation—watch for “slow acetylators”
Used alone or in combination with other drugs
Contraindicated with liver disease
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16. Classroom Response Question
A patient with a diagnosis of tuberculosis (TB) will be taking isoniazid (INH) as part of the anti-TB therapy. When reviewing the patient’s chart, the nurse finds documentation that the patient is a “slow acetylator.” This means that:
the dosage of INH may need to be lower to prevent INH accumulation.
the dosage of INH may need to be higher due to the slow acetylation process.
he should not take INH.
he will need to take a combination of anti-TB drugs for successful therapy.
Correct answer: A
Rationale: When INH is taken by slow acetylators, the INH accumulates because there are not enough liver enzymes to break down the INH. Therefore, the dosages of INH may need to be adjusted downward to prevent toxicity.
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17. Antitubercular Therapy: Indications
Used for the prophylaxis and treatment of TB
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Adverse Effects
INH
Peripheral neuropathy, hepatotoxicity
ethambutol
Retrobulbar neuritis, blindness
rifampin
Hepatitis; discoloration of urine, stools, and other body fluids
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19. Classroom Response Question
A patient is receiving isoniazid (INH) for the treatment of tuberculosis. Which vitamin does the nurse anticipate administering with the INH to prevent isoniazid-precipitated peripheral neuropathies?
Vitamin C
Vitamin B12
Vitamin D
Vitamin B6
Correct answer: D
Rationale: Pyridoxine (vitamin B6) may be indicated to prevent isoniazid-precipitated peripheral neuropathies and numbness, tingling, or burning of the extremities.
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Nursing Implications
Obtain a thorough medical history and assessment
Perform liver function studies in patients who are to receive INH or rifampin (especially in elderly patients or those who use alcohol daily)
Assess for contraindications to the various drugs, conditions for cautious use, and potential drug interactions
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21. Nursing Implications (cont’d)
Patient education is critical
Therapy may last for up to 24 months
Take medications exactly as ordered, at the same time every day
Emphasize the importance of strict adherence to regimen for improvement of condition or cure
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22. Classroom Response Question
Four weeks after beginning antitubercular drug therapy on an outpatient basis, the patient reports that he still experiences night sweats. What does the nurse identify as the main concern at this time?
He is not taking his medication properly.
More time is needed to see a therapeutic response.
His infection may be resistant to the drug therapy ordered.
He may have contracted a different strain of tuberculosis (TB).
Correct answer: C
Rationale: The nurse should not jump to conclusions that the patient is not taking his medication properly. An improvement should start to occur within 2 weeks of starting drug therapy, but this may not occur if the patient’s TB is not sensitive to the prescribed drugs. An evaluation of the drug therapy will be needed.
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23. Nursing Implications (cont’d)
Patient education is critical (cont’d)
Remind patients that they are contagious during the initial period of their illness—instruct in proper hygiene and prevention of the spread of infected droplets
Teach patients to take care of themselves, including adequate nutrition and rest
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24. Nursing Implications (cont’d)
Patients should not consume alcohol while on these medications or take other medications, including over-the-counter medications, unless they check with their prescriber
Rifampin causes oral contraceptives to become ineffective; another form of birth control will be needed
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25. Nursing Implications (cont’d)
Patients who are taking rifampin should be told that their urine, stool, saliva, sputum, sweat, or tears may become reddish orange; even contact lenses may be stained
Pyridoxine may be needed to combat neurologic adverse effects associated with INH therapy
Oral preparations may be given with meals to reduce gastrointestinal upset, even though recommendations are to take them 1 hour before or 2 hours after meals
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26. Nursing Implications (cont’d)
Monitor for adverse effects
Instruct patients on the adverse effects that should be reported to the prescriber immediately
These include fatigue, nausea, vomiting, numbness and tingling of the extremities, fever, loss of appetite, depression, jaundice
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27. Nursing Implications (cont’d)
Monitor for therapeutic effects
Decrease in symptoms of TB, such as cough and fever
Lab studies (culture and sensitivity tests) and chest x-ray should confirm clinical findings
Watch for lack of clinical response to therapy, indicating possible drug resistance
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28. Classroom Response Question
A patient has an extremely severe infection with a Mycobacterium that is resistant to all but one antitubercular drug; however, the patient has had an allergic reaction to that drug in the past. What does the nurse anticipate as being ordered for this patient?
A combination of antitubercular drugs will be chosen to fight the infection.
The patient will receive the drug and supportive care to help him tolerate the antitubercular therapy.
The patient will remain on isolation precautions until his cough clears.
There is nothing that can be done with this patient.
Correct answer: B
Rationale: It must be recognized that the urgency of treating a potentially fatal infection may have to be balanced against any prevailing contraindications. In extreme cases, patients are sometimes given a drug to which they have some degree of allergy with supportive care that enables them at least to tolerate the medication. Examples of such supportive care are treatment with antipyretics (e.g., acetaminophen), antihistamines (e.g., diphenhydramine), or even corticosteroids (e.g., prednisone, methylprednisolone).
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Case Study
A home care nurse is visiting a patient with a diagnosis of TB. The patient traveled abroad two months ago. He lives with his wife and 5-year-old son. The patient tells the nurse that he is concerned his son will also get TB so he wants to share his pills with his son. What is the best response by the nurse?
“That is a good idea. Children should not be exposed to TB.”
“You should give your son half of the dose you take.”
“Do not share any of your medications with anyone. Contact your son’s health care provider to discuss your concerns.”
“Children have an immune system that makes them immune to TB.”
Correct answer: C
Rationale: Medications of any kind should never be shared with any other person. In particular, antitubercular drugs are age specific. Assessment of age is also important, because the likelihood of adverse reactions and toxicity is increased in elderly patients due to age-related liver and kidney dysfunction. Additionally, the safety of these drugs in children 13 years of age and younger has not been established.
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Case Study (cont’d)
The patient tells the nurse, “I had a shot after I returned from my trip overseas. I thought that was supposed to stop me from getting a tuberculosis infection.” What information regarding tuberculosis- related injections does the nurse identify as being true?
BCG is used to prevent infection with tuberculosis for women of childbearing age.
A positive result for a PPD test is indicated by redness at the site of injection.
PPD is a diagnostic injection given intradermally to detect exposure to the TB organism.
BCG is a vaccine injection derived from an activated strain of Mycobacterium bovis.
Correct answer: C
Rationale: PPD is a diagnostic injection given intradermally in doses of 5 tuberculin units (0.1 mL) to detect exposure to the TB organism. A positive result is indicated by induration (not erythema) at the site of injection and is known as the Mantoux reaction, named for the physician who described it. BCG is used in much of the world to vaccinate young children against tuberculosis. Although it does not prevent infection, evidence indicates that it reduces active tuberculosis by 60% to 80% and is even more effective at preventing more severe cases involving dissemination of infection throughout the body.
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Case Study (cont’d)
The patient’s wife is taking rifampin to prevent her from developing a tuberculosis infection. Which statement by the wife indicates that further teaching is needed?
“Because my oral contraceptives will not work while I am taking rifampin, I will use another form of birth control.”
“I will take the medication for one week and then stop.”
“I will avoid prolonged exposure to the sun.”
“My urine may turn a reddish color when taking rifampin.”
Correct answer: B
Rationale: Antitubercular therapy is taken for long periods of time, often 24 months. Although this patient does not have an active infection at this time and is taking the rifampin to prevent an infection, the nurse should further investigate the length of time the medication is ordered. All other statements are true.
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