Lippincott Chapter 41: Antimycobacterial Drugs

Question 1

41.1 A 35-year-old male, formerly a heroin abuser, has been
on methadone maintenance for the last 13 months. Two
weeks ago, he had a positive tuberculosis skin test (PPD
test), and a chest radiograph showed evidence of right
upper lobe infection. He was started on standard four-drug
antimycobacterial therapy. He has come to the emergency
department complaining of “withdrawal symptoms.” Which
of the following antimycobacterial drugs is likely to have
caused this patient’s acute withdrawal reaction?
A. Ethambutol.
B. Isoniazid.
C. Pyrazinamide.
D. Rifampin.
E. Streptomycin.

Answer 1

Correct answer = D. Rifampin is a potent inducer of cyto-
chrome P450–dependent drug-metabolizing enzymes. The
duration of action of methadone is dependent upon hepatic
clearance, so enhanced drug metabolism will shorten the
duration and increase the risk of withdrawal symptoms in
individuals on methadone maintenance. None of the other
drugs listed induce cytochrome P450 enzymes.

Question 2

41.2 A 42-year-old male HIV patient was recently diagnosed
with active tuberculosis. Currently, he is on a stable HIV
regimen consisting of two protease inhibitors and two
nucleoside reverse transcriptase inhibitors (NRTIs).
What is the most appropriate regimen to use for
treatment of his tuberculosis?
A. Rifampin + isoniazid + pyrazinamide + ethambutol.
B. Rifabutin + isoniazid + pyrazinamide + ethambutol.
C. Rifapentine + isoniazid + pyrazinamide +
ethambutol.
D. Rifampin + moxifloxacin + pyrazinamide +
ethambutol.
E. Amikacin + moxifloxacin + cycloserine +
streptomycin.

Answer 2

Correct answer = B. Rifabutin is recommended in place of
rifampin in patients coinfected with HIV, since it is a less
potent inducer of CYP enzymes than rifampin. However,
rifabutin is a CYP3A4 substrate and “bidirectional” interac-
tions may result. Other medications, such as the protease
inhibitors, may affect the concentration of rifabutin, requir-
ing a dose adjustment. Answer E is incorrect as these are
not first-line agents.

Question 3

41.3 Which of the following is correct regarding clofazimine
in the treatment of leprosy?
A. Clofazimine should not be used in patients with a
deficiency in glucose-6-phosphate dehydrogenase
(G6PD).
B. Peripheral neuropathy is one of the most common
adverse effects seen with the drug.
C. Clofazimine may cause skin discoloration over time.
D. The risk of erythema nodosum leprosum is
increased in patients given clofazimine.

Answer 3

Correct answer = C. Clofazimine is a phenazine dye and will
cause bronzing (the skin pigment color will change color,
from pink to brownish-black), especially in fair-skinned
patients. This occurs in a majority of patients, and generally
is not considered harmful but may take several months to
years to fade after discontinuing the medication.

Question 4

41.4 A 24-year-old male has returned to the clinic for
his 1-month check-up after starting treatment for
tuberculosis. He is receiving isoniazid, rifampin,
pyrazinamide, and ethambutol. He states he feels
fine, but now is having difficulty reading his morning
newspaper and feels he may need to get glasses.
Which of the following drugs may be causing his decline
in vision?
A. Isoniazid.
B. Rifampin.
C. Pyrazinamide.
D. Ethambutol.

Answer 4

Correct answer = D. Optic neuritis, exhibited as a decrease
in visual acuity or loss of color discrimination, is the most
important side effect associated with ethambutol. Visual
disturbances generally are dose related and more common
in patients with reduced renal function. They are reversible
(weeks to months) if ethambutol is discontinued promptly.