TB Drugs Quiz Flashcards
Match the correct statements:
Rifampin
Isoniazid
Pyrizinamide
Most reported side effects of RIPE include
A) Discoloration of body fluids; hepatitis; loss of visual acuity
B) Is structurally related to nicotinamide (niacin)
C) Is structurally similar to pyridoxine and promotes the excretion of pyridoxime
D) Can increase the metabolism of certain medications eliminated by the liver
Rifampin - D
Isoniazid - C
Pyrizinamide - B
Most reported side effects of RIPE include - A
T or F: Baseline measurements of liver function and visual acuity should be obtained before initiating therapy with a four-drug regimen of isoniazid, rifampin, and pyrazinamide plus either ethambutol or streptomycin. Neither ethambutol nor streptomycin adds substantially to the overall activity of the regimen (ie, the duration of treatment cannot be further reduced if either drug is used), but they provide additional coverage if the isolate proves to be resistant to isoniazid, rifampin, or both.
True
T or F: Isoniazid as a single agent is also indicated for treatment of latent tuberculosis. The dosage is 300 mg/d (5 mg/kg/d) or 900 mg twice weekly for nine months.
True
Your patient is diagnosed with pulmonary tuberculosis, and started on therapy. On her release from the hospital, you advise her to not rely solely on oral contraceptives to prevent pregnancy because they may be less effective while she is being maintained on antimycobacterial drugs. The agent most likely to interfere with the action of oral contraceptives is:
A) Isoniazid
B) Ethambutol
C) Pyrazinamide
D) Rifampin
D - rifampin includes the formation of several microsomal drug-metabolizing enzymes, including cytochrome P450 isoforms. This action increases the rate of elimination of a number of drugs, including anticoagulants, ketoconazole, methadone, and steroids that are present in oral contraceptives. The pharmacologic activity of these drugs can be reduced markedly in patients taking rifampin.
Which statement about antitubercular drugs is accurate?
A) Antimycobacterial actions of streptomycin involve inhibition of arabinosyltransferases
B) Cross-resistance of M tuberculosis to isoniazid and pyrazinamide is common
C) Ocular toxicity of ethambutol is prevented by thiamine
D) Resistance to ethambutol involves mutations in the emb gene
D - Arabinosyltransferase is inhibited by ethambutol (not streptomycin) and resistance involves alterations in the emb gene. Ocular adverse effects of ethambutol are dose dependent and usually reversible when the drug is discontinued. Thiamine is not protective. There is minimal cross-resistance between pyrazinamide and other antimycobacterial drugs. Pyrazinamide uniformly causes hyperuricemia, but this is not a reason to halt therapy even though the drug may provoke gouty arthritis in susceptible persons.
A 45-year-old homeless man presents to the emergency department with fever, weight loss, and a productive cough. Chest x-ray shows right apical infiltrate. You suspect TB . After consultation you decide to start empiric INH, rifampin, and pyrazinamide. The primary reason for the use of drug combinations in the treatment of this patient’s TB is:
A) Delay or prevent the emergence of resistance
B) Ensure patient compliance with the drug regimen
C) Reduce the incidence of adverse effects
D) Provide prophylaxis against other bacterial infections
E) Increase antibacterial activity synergistically
A - although it is sometimes possible to achieve synergistic effects against mycobacteria with drug combinations, the primary reason for their use is to delay the emergence of resistance.
A 12-year-old boy has uncomplicated pulmonary tuberculosis. After initial hospitalization, he is now treated at home with isoniazid, rifampin, and ethambutol. Which statement about this case is accurate?
A) A baseline test of auditory function is essential before drug treatment is initiated
B) His mother, who takes care of him, does not need INH prophylaxis
C) The potential nephrotoxicity of the prescribed drugs warrants periodic assessment of renal function
D) His 3 year old sibling should receive INH prophylaxis
D - a baseline test of ocular (not auditory) function may be useful before starting ethambutol. None of the drugs prescribed are associated with nephrotoxicity. Periodic tests of liver function may be advisable in younger patients who are treated with INH plus rifampin, especially if higher doses of these drugs are used. Prophylaxis with INH is advisable for all household members and very close contacts of patients with active tuberculosis, especially young children.
A 20-year-old woman from Southeast Asia is staying with family members in the United States over the last 3 mo and looks after her sister’s preschool children during the day. Because she has difficulty with the English language, her sister escorts her to the emergency department of a local hospital. She tells you that her sister has been feeling very tired for the last month, has a poor appetite, and has lost weight. The patient has been feeling somewhat better lately except for a cough that produces a greenish sputum, sometimes specked with blood. With the exception of rales in the left upper lobe, the physical examination is unremarkable and she does not seem to be acutely ill. Laboratory values show a white count of 12,000/µL and a hematocrit of 33%. Chest x-ray film reveals an infiltrate in the left upper lobe with a possible cavity. A Gram-stained smear of the sputum shows mixed flora with no dominance. An acid-fast stain reveals many thin rods of pinkish hue. A preliminary diagnosis is made of pulmonary tuberculosis. Sputum is sent to the laboratory for culture.
Which drug regimen should be initiated in this patient when treatment is started?
A) Amikacin, isoniazid, pyrazinamide, streptomycin
B) Ethambutol, isoniazid, pyrazinamide, rifampin
C) Ciprofloxacin, cycloserine, isoniazid, PAS
D) PAS, pyrazinamide, rifabutin, streptomycin
B - sputum cultures will not be available for several weeks, and no information is available regarding drug susceptibility of the organism at this stage. For optimum coverage, the initial regimen should include INH, rifampin, pyrazinamide, and ethambutol. INH-resistant organisms are usually sensitive to both rifampin and pyrazinamide. Streptomycin is usually reserved for use in severe forms of tuberculosis or for infections known to be resistant to first-line drugs. Likewise, amikacin and ciprofloxacin are possible agents of treatment for multidrug-resistant strains of M tuberculosis. Cycloserine, PAS, and rifabutin are alternative second-line drugs that may be used in cases of failed response to more conventional agents.
A 35 y/o woman is admitted to the hospital with a 4-week history of cough and fever. A chest x-ray showed upper left lobe cavitary infiltrate. Cultures of sputum yielded M. tuberculosis susceptible to all antimycobacterial drugs. The patient received self-administered isoniazid, rifampin, pyrazinamide, and ethambutol. Two weeks following initiation of therapy, the patient is concerned that her vision is blurry. Which of the following drugs is the most likely cause?
A) INH
B) Rifampin
C) Ethambutol
D) Pyrazinamide
C - ethambutol, even at standard doses, can cause ocular toxicity, including blurred vision and red-green color blindness. Visual disturbances are reversible (weeks to months) if ethambutol is discontinue promptly.
