Acyclovir is a nucleoside analog medication. Specifically, it is a guanosine analog, and lacks a free 3' group, which is necessary for addition of the next nucleotide. Thus, when added to a growing DNA chain, synthesis is halted.
Acyclovir inhibits viral replication through the mechanism of suppressing synthesis of viral DNA. Acyclovir is activated within cells infected with herpes simplex virus or varicella zoster virus. This medication directly targets the thymidine kinase formed by herpesviruses and does not affect human DNA.
This medication used viral thymidine kinase to convert it into acyclovir monophosphate. This is converted into another compound, which then inactivates and competitively inhibits DNA polymerases, halting DNA synthesis in viral cells.
Acyclovir decreases the symptoms of oral and genital herpes, but does not eliminate the virus. Topical acyclovir is indicated for initial genital herpes simplex virus. Oral acyclovir is effective against both initial and recurrent oral and genital herpes infections. Intravenous acyclovir is indicated for patients with severe genital herpes infection, or immunocompromised patients with oral herpes.
Oral acyclovir is given to patients with varicella (chickenpox) within 24 hours of developing a rash. Older adults with herpes zoster (shingles) are administered high doses of oral acyclovir. Immunocompromised patients with varicella zoster virus are given intravenous acyclovir.
Headache and vertigo are common mild neurological side effects of oral acyclovir. Warn the patient about the possibility of developing headaches before administering this medication.
Acyclovir has a low bioavailability and is slowly absorbed by the GI tract. This medication may cause symptoms of GI distress, such as nausea, vomiting, and diarrhea.
Patients with renal impairment have a decreased ability to excrete medications. A buildup of acyclovir in the patient's body may cause neurotoxicity as evidenced by agitation, tremors, hallucinations, and delirium. The patient may present with myoclonus or a sudden involuntary jerking movement.
Acyclovir may affect the renal tubules and cause increased BUN and creatinine levels indicating nephrotoxicity. Slowly infusing the medication over one hour and ensuring adequate hydration may minimize kidney damage.
The herpes simplex virus is spread through kissing, skin-to-skin contact and intercourse. Oral acyclovir may be administered prophylactically to prevent recurrence of cold sores. To avoid spreading the virus, instruct the patient to always use a condom and to abstain from all sexual contact while symptomatic. To prevent newborn transmission during delivery, pregnant women with genital herpes may be treated with acyclovir closer to term.
Administer IV acyclovir slowly over one hour to minimize kidney damage caused by the medication accumulation in the renal tubules. Do not administer acyclovir by IV bolus or else renal damage may occur.
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