Updated: 3/14/2018

Reverse Transcriptase Inhibitors

Topic
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Introduction
  • Classification
    • antiviral
      • reverse transcriptase inhibitors
  • Drugs
    • nucleoside RTIs (NRTIs)
      • zidovudine (ZDV, formerly AZT)
      • didanosine (ddI)
      • zalcitabine (ddc)
      • lamivudine (3TC)
      • stavudine (d4T)
      • tenofovir (TDF)
        • technically a nucleotide analog, not a nucleoside analog
      • emtricitabine (FTC)
      • abacavir (ABC)
    • non-nucleoside RTIs (NNRTIs)
      • neVIRapine
      • efaVIRenz
      • delaVIRdine
Mechanism
  • Action
    • competitively inhibit viral reverse transcriptase (RNA-dependent DNA polymerase)
    • incorporated into viral genome, stopping DNA synthesis
      • lack of free 3'-OH prevents 3' -> 5' phosphodiester linkage to the next nucleotide
    • NRTIs
      • must be phosphorylated by thymidine kinase to be active
      • competitively inhibit reverse transcriptase
      • incorporated into DNA to terminate DNA chains
    • NNRTIs
      • are not activated by phosphorylation
      • noncompetitively inhibit reverse transcriptase
      • are not incorporated into DNA
  • Resistance
    • via mutations in the pol gene
    • occurs rapidly if drugs are used in monotherapy
Uses
  • HAART (against HIV)
    • in combination with protease inhibitors
    • begin treatment when CD4 count is low (<500) and viral load is high
  • HIV prophylaxis
    • especially zidovudine (ZDV)
    • either general prophylaxis or to prevent mother-fetus transmission
Adverse effects
  • NRTIs
    • myelosuppression
      • especially neutropenia and anemia
      • use G-CSF and erythropoietin to alleviate
    • peripheral neuropathy and lactic acidosis
      • especially didanosine, zalcitabine, stavudine
      • avoid using these 3 in combination with each other
    • pancreatitis
      • seen with didanosine
    • megaloblastic anemia
      • especially zidovudine
    • side effects unusual with lamivudine
  • NNRTIs
    • hepatotoxicity
    • rash
    • NO myelosuppression
 

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