chapter 24 antimycobacterials

Question 1

pharmacodynamics/pharmacokinetics of antimycobacterials

Answer 1

• isoniazid (INH) and ethambutol inhibit synthesis of mycolic acids
• rifampin binds and inhibits RNA synthesis
• ethambutol inhibits synthesis of arabinogalctan (needed for cell walls)
• po well absorbed
• metabolism varies-dependent on acetylator status-genetic liver metabolism; does not impact therapeutic effect but toxicity

Question 2

keep in mind when prescribing antimycobacterials (L.U.N.G.S.)

Answer 2

L: liver enzymes
U: use cautiously with renal failure
N: no ETOH
G: give B6 prophylactically to prevent peripheral neuropathy
S: should take on empty stomach

Question 3

ADRs of mycobacterials

Answer 3

• INH: peripheral neuropathy
• INH, rifampin, pyraziamide: hepatotoxicity
  ethambutol: optic neuritis
• streptomycin, capreomycin: ototoxic
• rifabutin: neutropenia, thrombocytopenia
• rifampin is inducer of CYP450 enzyme

Question 4

clinical use of antimycobacterials

Answer 4

• TB
• follow CDC guidelines
• preventative therapy-INH
• low compliance rate-length of therapy

Question 5

mycobacteria

Answer 5

• slowly growing-therefore resistant to drugs dependent on rapid cell division
• lipid rich wall-difficult for drugs to penetrate
• found intracellularly-inaccessible to drugs
• ability to be dormant
• easily develop resistant to single drug therapy