Antimycobacterials Rational Drug Selection - Answer · follow CDC guidelines -many
other uses for rifampin that are not mycobacterial infections
Antimycobacterials Pharmacodynamics - Answer · Isoniazid: most active for TB
treatment --interferes w/ lipid and nucleic acid biosynthesis in growing organisms --
bacteriocidal (intracellular and extracellular)-Isoniazid and ethambutol-inhibit synthesis
of mycolic acids (important for mycobacterial cell walls) -Rifamycins (rifampin, rifabutin,
rifapentine): binds to subunit of mycobacteria DNA-dependent RNA polymerase and
inhibits RNA synthesis -bactericidal -Ethambutol: inhibits synthesis of arabinogalactan,
essential bacterial cell wall component; also stops cell multiplication causing cell death
Drug interactions- -vary by drug -Rifamycins: potent inducers of CYP450 and speed
metabolism of many drugs, causing therapeutic failure
Antimycobacterials Pharmacokinetics - Answer Rapidly absorbed in GI tract -Isoniazids
Need to be taken on empty stomach-Metabolized in liver -Isoniazid metabolism is highly
variable and dependent on acetylator status Excreted in urine, bile
Antimycobacterials Pharmacotherapeutics - Answer Precautions/Contraindications -
Renal and hepatic impairment Ethambutol, pyrazinamide: Gouty arthritis -pregnant, or
immediately postpartum -Rifampin: CYP450 inducer -Isoniazid=Pregnancy Cat A, most
others: C, streptomycin: D
Antimycobacterials Clinical indications & dosing - Answer Tuberculosis infection --four
drugs req'd (INH, RIF, PZA, and EMB) x2months --then continuation drugs (INH and
another drug, usually RIF) x4-7 months -HIV has phase protocols -preventative drug
therapy w/ INH
Antimycobacterials ADRs - Answer Hypersensitivity -INH: Peripheral neuropathy (most
common for INH); pyridoxine for prophy while taking INH -INH, rifampin, pyrazinamide:
hepatotoxicity -INH: blood dyscrasias, metabolic acidosis, drug fever, gynecomastia -
Rifamycins: GI, discolored body fluids (orange red), blood dyscrasias, HA, drowsiness,
inability to concentrate, pruritic rash, lupus -Streptomycin, capreomycin: ototoxic -
Rifabutin: neutropenia and thrombocytopenia -GI reactions -Ethambutol: optic neuritis
Antimycobacterials Pt Education - Answer Essential education d/t length of tx -Report
ADRs --take w/ food if GI upset -Rifamycin discolors bodily fluids -Ethambutol: report
vision changes or eye pain
, NR565 Week 6 Study Guide
Antivirals Spectrum of Coverage - Answer Antiviral drugs target the steps of viral
replication:1. absorption to and penetration into susceptible cells 2. uncoating of viral
nucleic acid 3.synthesis of early, regulatory proteins 4. synthesis of RNA or DNA 5.
synthesis of late, structural proteins 6. assembly of viral particles 7. release from the cell
-Many antivirals act on step 4 -Antivirals must either block entry into the cell or be active
inside host cells -they're nonselective, so damage to host cells occurs
Antivirals Pharmacodynamics - Answer Acyclovir, valacyclovir -Pharmacodynamics -
Acyclovir --Converted to monophosphate derivative by virus-specific thymidine kinase --
Then to di- and triphosphate compounds by host's cellular enzymes --Inhibits viral DNA
synthesis -Valacyclovir --Converted to acyclovir -Famciclovir -metabolized to
penciclovir; similar activity as acyclovir. Antiviral drugs must either block entry into the
cells or be active inside host cells to be effective Acyclovir: active against herpes
simplex viruses 1 and 2 (HSV-1 and HSV-2); varicella-zoster virus (VZV); Epstein-Barr
virus (EBV), cytomegalovirus (CMV), and herpes virus 6 Valacyclovir is converted to
acyclovir after oral administration and is active against the same viruses Famciclovir:
active against HSV-1 and HSV-2, VZV, EBV, and hepatitis B virus Ganciclovir is active
against CMV
Antivirals Rational drug selection - Answer Choice based on cost and convenience
Antivirals Pharmacokinetics - Answer Acyclovir poorly absorbed orally, therapeutic
levels are achieved -Topical for herpatic lesions, not systemic -Eliminated in urine
unchanged: dosage adjustments needed for renal impairment
Antivirals Rational drug selection - Answer based on cost and convenience; all in this
class are equally effective against HSV infections. -Initiate tx w/in 48hrs of onset of
illness -rapid flu test to confirm -drug selection depends on ADRs, cost, convenience
Antivirals Clinical indications & dosing - Answer Herpes simplex virus: genital herpes,
both initial outbreak and suppression therapy Herpes zoster (shingles): Start therapy
within 3 days of outbreak. Varicella (chickenpox): Start within 24 hours of outbreak
Gingivostomatitis in children Bell's palsy. -Infections by HSV virus -Primary care: genital
lesions (initial outbreak and suppression tx), herpes zoster (shingles; start tx w/in 3 days
of outbreak), varicella (chicken pox; start tx w/in 24hrs of outbreak), and
gingivostomatitis in kids -Increase rate of healing, do not prevent recurrences -Should
be initiated as soon as possible after onset of recurrent episode -dosing interval, dosage
amount, or both adjusted for renal impairment -Bell's palsy prophy -Herpes simplex
prophy in immune comp'd
Antivirals ADRs - Answer few ADRs when given orallyValacyclovir may cause
thrombocytopenia purpura, hemolytic uremic syndrome in immunocompromised
patients. Famciclovir: headache Ganciclovir: granulocytopenia, anemia and
thrombocytopenia; may be carcinogenic Drug interactions: Few
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