questions 4

Acyclovir

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Topic updated on 12/11/16 5:22am

Introduction
  • Classification
    • antiviral
      • viral DNA polymerase inhibitors
        • acyclovir
  • Drugs
    • acyclovir
Mechanism
  • Both acyclovir and ganciclovir are guanosine analogs dependent on phosphorylation for activation
    • the main difference between the 2 drugs lies in the mechanism by which they are phosphorylated
  • Action of acyclovir
    • monophosphorylated by HSV/VZV thymidine kinase
      • most herpesviridae have this kinase → kills herpesviridae
      • CMV does not have this kinase → less effective against CMV
      • human cells do not have this kinase → low toxicity to human cells
    • further phosphorylated by host cells to form triphosphate
    • acyclovir-triphosphate is incorporated into DNA molecule and terminates the chain
  • Resistance
    • via lack of thymidine kinase
Uses
  • Generally reserved for serious infections or immunocompromised
  • HSV
    • lesions
    • encephalitis
    • no effect on latent virus
  • VZV (varicella zoster)
    • prophylaxis in immunocompromised
    • reduce symptoms of chickenpox in early stages
    • no effect on latent virus
    • famciclovir preferred for shingles
  • EBV
Adverse effects
  • Usually well tolerated
  • Not hematotoxic (ganciclovir is)
  • Neurotoxicity
  • Renal failure secondary to crystalline nephropathy  
  • Must prehydrate to decrease the risk 


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Qbank (2 Questions)

TAG
(M1.MC.14) A 35-year-old man with a past medical history of HIV is hospitalized with a disseminated zoster infection and treated with IV acyclovir. His course of illness worsens on the 4th day after admission and his creatinine level increases to 4.2 mg/dL. Urinalysis shows birefringent needle-shaped crystals. What could have prevented this deterioration in the patient's renal function? Topic Review Topic

1. Initial administration of glucocorticoids
2. Monitoring of drug levels
3. Obtaining a thorough history of patient allergies
4. Adequate initial hydration
5. Initial administration of allopurinol

PREFERRED RESPONSE ▶
TAG
(M1.MC.106) A 69-year-old female with acute myelogenous leukemia is admitted for bone marrow transplant. Her initial course is uncomplicated. On day 10, she becomes profoundly ill and is diagnosed with disseminated herpes simplex virus. The resident discovers that acyclovir prophylaxis was omitted from her daily orders. She is immediately treated with high-dose intravenous acyclovir and her symptoms resolve. In the midst of receiving this therapy, her creatinine triples from her baseline and her potassium rises above the normal range. Urinalysis shows the following seen in Figure A. Which of the following drugs might result in a similar complication? Topic Review Topic
FIGURES: A          

1. Sulfadiazine
2. Metronidazole
3. Oxycodone
4. Lisinopril
5. Atorvastatin

PREFERRED RESPONSE ▶


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