Antimycobacterial Drugs Flashcards by Jamaira Belmes

Test the TB EXPOSURE

Mandoux (Mendel-Mantoux) Test/ Tuberculin Skin Test/ Purified Protein Derivative

TYPE IV HYPERSENSITIVITY

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MOA of Rifampicin

(-) DNA-dependent RNA polymerase –> (-) RNA production

BACTERICIDAL

NUCLEIC ACID

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Side effects of Rifampicin

Red-orange body fluids

Hepatotoxic

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Mechanism of Resistance in Rifampicin

rPOB gene

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MOA of Isoniazid

(-) mycolic acid synthesis

BACTERICIDAL

CELL WALL

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Side effects of Isoniazid

hepatitis
neurotoxic (peripheral neuropathy) - give PYRIDOXINE (B6)
drug induced lupus

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Mechanism of Resistance in Isoniazid

KATG gene

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MOA of Pyrazinamide

Converted to PYRAZINOIC ACID (active form) under the acidic conditions of macrophage lysosomes

BACTERIOSTATIC
BACTERICIDAL - actively dividing cells
STERILIZING AGENT

INTRACELLULAR

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Mechanism of Resistance in Pyrazinamide

pnCA gene

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Side effects of Pyrazinamide

MOST HEPATOTOXIC

HYPERURICEMIA

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MOA of Ethambutol

(-) ARABINOSYL TRANSFERASE
involved in the synthesis of arabinogalactan in mycobacterial cell wall

BACTERIOSTATIC

CELL WALL

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Mechanism of Resistance in Ethambutol

embCAB gene

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Side effects of Ethambutol

visual disturbances - optic neuropathy

RED-GREEN color blindness

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MOA of Streptomycin

(-) protein synthesis by (-) 30s subunit

EXTRACELLULAR

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Side effects of Streptomycin

nephrotoxic
ototoxic
congenital deafness
VESTIBULOTOXIC

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Kills actively multiplying organisms

Bactericidal

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All 1st line are bactericidal EXCEPT

ETHAMBUTOL - bacteriostatic

Ability to KILL all remaining organisms

STERILIZING

steRiliZing

RIFAMPICIN
PYRAZINAMIDE

Last resort in the treatment of MDR-TB

Clofazimine

Novel anti-TB meds that (-) mycobacterial ATP synthase (complex V of ETC)

Bedaquiline

Novel anti-TB meds that (-) mycolic acid synthesis

Delamanid

MOA of Dapsone

(-) folic acid synthesis

BACTERIOSTATIC

leprosy, PCP

Most active drug against M. leprae

Dapsone

Binds to GUANINE bases in bacterial DNA

Clofazimine

BACTERICIDAL

Treatment for atypical mycobacterium

Azithromycin or Clarithromycin PLUS Ethambutol AND Rifabutin

Prophylaxis for atypical mycobacterium

Azithromycin or Clarithromycin +/- Rifabutin (in px CD4 <50)

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 and TB is suspected. He is started on 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) Increase antibacterial activity synergistically (D) Provide prophylaxis against other bacterial infections (E) Reduce the incidence of adverse effects

(A) Delay or prevent the emergence of resistance

On her release from the hospital, the patient is advised not to 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) Amikacin (B) Ethambutol (C) Isoniazid (D) Pyrazinamide (E) Rifampin ```

(E) Rifampin Rifampin induces the formation of several microsomal drugmetabolizing 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

A patient with AIDS and a CD4 cell count of 100/µL has persistent fever and weight loss associated with invasive pulmonary disease due to M avium complex (MAC). Optimal management of this patient is to (A) Choose an antibiotic based on drug susceptibility of the cultured organism (B) Initiate a two-drug regimen of INH and pyrazinamide (C) Prescribe rifabutin because it prevents the development of MAC bacteremia (D) Start treatment with the combination of azithromycin, ethambutol, and rifabutin (E) Treat with trimethoprim-sulfamethoxazole

(D) Start treatment with the combination of azithromycin, ethambutol, and rifabutin

A 10-year-old boy has uncomplicated pulmonary tuberculosis. After initial hospitalization, he is now being treated at home with isoniazid, rifampin, and ethambutol. Which statement about this case is accurate? (A) A baseline test of auditory function test is essential before drug treatment is initiated (B) His mother, who takes care of him, does not need INH prophylaxis (C) His 3-year-old sibling should receive INH prophylaxis (D) Polyarthralgia is a potential adverse effect of the drugs the boy is taking (E) The potential nephrotoxicity of the prescribed drugs warrants periodic assessment of renal function

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) Pyrazinamide treatment should be discontinued immediately if hyperuricemia occurs (E) Resistance to ethambutol involves mutations in the emb gene

(E) Resistance to ethambutol involves mutations in the | emb gene

``` Once-weekly administration of which of the following antibiotics has prophylactic activity against bacteremia caused by M avium complex in AIDS patients? (A) Acedapsone (B) Azithromycin (C) Clarithromycin (D) Kanamycin (E) Rifabutin ```

(B) Azithromycin Because of its long elimination half-life (3–4 d), weekly administration of azithromycin has proved to be equivalent to daily administration of clarithromycin when used for prophylaxis against M avium complex in AIDS patients. Acedapsone is a repository form of dapsone used in leprosy

Risk factors for multidrug-resistant tuberculosis include (A) A history of treatment of tuberculosis without rifampin (B) Recent immigration from Asia and living in an area of over 4% isoniazid resistance (C) Recent immigration from Latin America (D) Residence in regions where isoniazid resistance is known to exceed 4% (E) All of the above

(E) All of the above

Rifampin derivative that is NOT absorbed in the GIT thus used for the PREVENTION of HEPATIC ENCEPHALOPATHY, TRAVELLER'S DIARRHEA

Rifaximin

Preferred anti TB for AIDS patients

Rifabutin

Most hepatotoxic anti TB drug

Pyrazinamide

Used in Drug Resistant TB Administered IM

Streptomycin

(-) folic acid synthesis bacteriostatic for leprosy, PCP pneumonia (backup) MOST ACTIVE DRUG AGAINST M. LEPRAE

Dapsone | Acedapsone

Binds to guanine bases in bacterial DNA bactericidal for sulfone resistance leprosy

Clofazimine

Used for LATENT TB

Isoniazid | Rifampicin