Acyclovir

MECHANISM OF ACTION:
  • The effect of acyclovir is based on a selective inhibition of the replication of herpes viruses. 
  • The drug is phosphorylated by viral thymidine kinase. 
  • As a triphosphate acyclovir inhibits the DNA polymerase and thus the formation of viral DNA. 
  • The host cells are not considerably affected. 
  • Varicella-zoster viruses are not as sensitive as herpes simplex viruses.
  • Resistant herpes viruses, that lack the thymidine kinase, have been observed almost exclusively in immunocompromised subjects.
INDICATIONS:
  • Herpes simplex: For genital primary infections, oral acyclovir entails a considerably faster healing rate than a placebo or an acyclovir ointment.
  • Systemic acyclovir in herpes zoster is useful When started immediately after the onset of rash
  • For herpes simplex keratitis, local or oral therapy is successful.
  • Herpes simplex encephalitis and herpes simplex neonatorum must be treated intravenously.
  • Patients with frequently relapsing herpes simplex (labial or genital) benefit from long-term, prophylactic acyclovir administration. However, treatment of an isolated (labial or genital) herpes relapse is not indicated.
  • Herpes zoster of the cornea should be treated as early as possible with high doses of acyclovir 
  • Ideal time for starting post-exposure prophylaxis with acyclovir in a person exposed to varicella is 7-9 th day
  • Indication of Acyclovir in pregnancy is in Disseminated herpes,Chicken-pox in first trimester & Prophylaxis in recurrent herpes 
  • Bell's palsy patient comes on day 3 can be treated with Oral steroids + Acyclovir 
ADVERSE EFFECTS:
  • Nausea or vomiting Upper abdominal pain, 
  • Causes oligouria
  • Headaches, or exanthema. 
  • Nephrotoxic
  • In approximately 1% of the treated patients, an encephalopathy (lethargy, confusion, agitation, cramps) can be observed after intravenous administration. 
Exam Question of:
  • Acyclovir inhibits viral polymerase activity to inhibit herpes virus replication
  • Bell's palsy patient comes on day 3 can be treated with Oral steroids + Acyclovir
  • Drugs of choice for corneal herpes is Acyclovir
  • Ideal time for starting post-exposure prophylaxis with acyclovir in a person exposed to varicella is 7-9 th day
  • Indication of Acyclovir in pregnancy is in Disseminated herpes,Chicken-pox in first trimester & Prophylaxis in recurrent herpes 
  • HSV encephalopathy is treated with acyclovir
  • Acyclovir inhibits DNA synthesis and viral replication
  • Oliguria causing drug is Acyclovir
  • Acyclovir is nephrotoxic 
  • Systemic acyclovir in herpes zoster is useful When started immediately after the onset of rash
  • Mechanism of Acyclovir resistance Thymidine kinase
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