Wednesday, December 8, 2021

Acyclovir: Uses, Indications, Dosages, Precautions, Contraindications, Side Effects & Interactions

Acyclovir: Uses, Indications, Dosages, Precautions, Contraindications, Side Effects & Interactions


Pharmacotherapeutic: Synthetic nucleoside
Clinical: Antiviral
Pregnancy Risk Category: B

General Information

Acyclovir is an antiviral drug used in the treatment of herpes infections, which can cause cold sores and genital herpes. It is available in the form of tablets, liquid, cream, eye ointment and injection. The cream is commonly used to treat cold sores and can speed up the healing of the lesions, provided it is started as soon as symptoms appear and the lesions appear. The tablets and injection are used to treat severe herpes infections, shingles, chicken pox, and genital herpes. The tablets can also be used to prevent the development of herpes infections in people who have reduced immunity. Herpes infection affecting the eye can be treated with eye ointment


Interferes with the synthesis of DNA by converting it into acyclovir triphosphate, which causes a decrease in viral replication

Therapeutic Effect

It interferes with DNA synthesis and viral replication. Virustatic

Availability (Rx)

Capsules: 200 mg
Tablets: 400 mg, 800 mg
Injection (lyophilized powder for
reconstitution): 50 mg/mL once
Oral Suspension: 200 mg/5 mL
Injection, Solution: 25 mg/mL
Cream: 5%
Ointment: 5%


Mucocutaneous herpes simplex virus, herpes genitalis (HSV-1, HSV-2), chickenpox infections, varicella infections, herpes zoster, herpes simplex encephalitis
Unlabeled uses: Bell’s palsy, prevention of CMV, Epstein-Barr virus, esophagitis, stomatitis, pharyngitis, hairy leukoplakia,keratoconjunctivitis, prevention of herpes labialis, herpes simplex, herpes simplex ocular prophylaxis, pneumonitis, tracheobronchitis, prevention of postherpetic neuralgia, proctitis, varicella prophylaxis


Pregnancy B, breastfeeding, renal/hepatic (liver) disease, electrolyte imbalance, dehydration, neurologic disease; hypersensitivity to famciclovir, ganciclovir, penciclovir, valganciclovir

Make sure to tell your doctor if:
• You have a long-term kidney problem
• You have reduced immunity
• You are taking other medicines

Indications and Dosages

‣ To Treat Genital herpes (initial episode)

 Adults, Elderly, Children 12 yr and older. 200 mg q4h 5 times / a day
 Cover all lesions every 3 h, 6 times a day for 7 days. Begin as soon as signs and symptoms occur
• Adults, Elderly, Children 12 yr and older. 5 mg/kg q8h for 5 days

‣To Treat Genital herpes (recurrent)

Less than 6 episodes per year:
• Adults, Elderly, Children 12 yr and older. 200 mg q4h 5 times / a day for 5 days.
6 episodes or more per year:
• Adults, Elderly, Children 12 yr and older. 400 mg 2 times / a day, or 200 mg 3-5 times / a day for up to 12 mo

‣ To Treat Herpes labialis (cold sores), recurrent

• Adults, Children 12 yr and older. Apply 5 times per day for 4 days (during the prodrome or when lesions appear)

‣ To Treat Herpes simplex mucocutaneous

• Adults, Elderly, Children 12 yr and older. 5 mg/kg/dose q8h for 7 days
• Children younger than 12 yr. 10 mg/kg q8h for 7 days

‣ To Treat Herpes simplex neonatal 

• Children younger than 4 mo. 10 mg/kg q8h for 10 days

‣ To Treat Herpes simplex encephalitis

• Adult: 10 mg/kg over 1 hr q8hr 3-10 days
• Child 3 mo-12 yr: 20 mg/kg q8hr 3-10 days
• Childbirth-3 mo: 10 mg/kg q8hr 3-10 days

‣ To Treat Herpes zoster (caused by varicella)

• Adults, Elderly, Children 12 yr and older. 10 mg/kg q8h for 7 days
• Children younger than 12 yr. 20 mg/ kg q8h for 7 days

 ‣ To Treat Herpes zoster (shingles) 

 Adults, Elderly, Children 12 yr and older. 800 mg q4h 5 times / a day for 7-10 days

‣ To Treat Varicella (chickenpox)

• Adults, Elderly, Children older than 12 yr or children 2-12 yr, weighing
40 kg or more. 800 mg 4 times / a day for 5 days
• Children 2-12 yr, weighing < 40 kg. 20 mg/kg 4 times a day for 5 days. Maximum: 800 mg/dose

‣ Dosage in renal impairment

The dose and frequency are adjusted according to the severity of the infection and the degree of renal impairment
• If normal dose is 800 mg 5 times/ a day, decrease to 800 mg q12h. If normal dose is 200 mg 5 times/day, or 400 mg q12h, decrease dose to 200 mg q12h
CCr .50 ml/min 100% dose q8hr, CCr. 25-50 ml/min 100% dose q12hr, CCr. 10-25 ml/min 100% dose q24hr, CCr. 0-10 ml/min 50% dose q24hr


Poorly absorbed from the gastrointestinal tract; minimal absorption after topical application. Protein bond: 9% -36%. Widely distributed. Penetrates CSF levels from approximately 13% to 52% of those in plasma. Partially metabolized without changes in the liver. It is mainly excreted unchanged in the urine. Removed by hemodialysis. Half-life: 2.5 h (increase in impaired renal function)


PO route

• Give with food to lessen gastrointestinal symptoms; may give without regard to meals with 8 oz of water
• Do not crush/break capsules.
• Store capsules at room temperature
• May be taken orally before infection occurs or when itching or pain occurs, usually before eruptions
• It should be taken at equal intervals around the clock
• Shake susp before use

IV route

• Provide more fluids at 3 L / day to reduce crystalluria, which is most critical during the first 2 hours after IV infusion

Intermittent IV infusion route

• Reconstitute with 10 ml sterile water for injection/ 500 mg of product (50 mg/ml); shake; further dilute in 50-125 ml compatible sol, use within 12 hr; give over at least 1 hr (constant rate) by infusion pump to avoid nephrotoxicity; do not reconstitute with sol containing benzyl alcohol or parabens; check infusion site for redness, pain, induration; rotate sites
• Lower dose in acute or chronic renal failure
• Store at room temperature for up to 12 hours after reconstitution; If refrigerated, sol may show a precipitate that clears at room temperature; yellow discoloration does not affect potency


• Avoid contact with eye
• Use finger cot, or rubber glove to avoid autoinoculation
• Apply to cover only cold sores or the area with symptoms.
• Rub until it disappears


Hypersensitivity to acyclovir or valacyclovir


Individual drugs

Aminoglycosides: increased nephrotoxicity Entecavir, PEMEtrexed, tenofovir: elevated concentration of each product
Probenecid: increased neurotoxicity, nephrotoxicity 
Valproic acid: reduced action of valproic acid Zidovudine, methotrexate IT: increased CNS side effects

Drug classifications

• Hydantoins: decreased actions of hydantoins

Drug/laboratory tests

• It can increase BUN and serum creatinine concentrations


• None known


• None significant

Side effects

CNS: Tremors, confusion, lethargy, hallucinations, seizures, dizziness, headache and encephalopathic changes
EENT: Gingival hyperplasia
GI: Nausea, vomiting, diarrhea, abdominal pain, glossitis, colitis, increased ALT/AST
GU: Oliguria, proteinuria, hematuria, vaginitis, changes in menses, moniliasis, acute renal failure, glomerulonephritis, polydipsia
HEMA: Thrombotic thrombocytopenia purpura, hemolytic uremic syndrome, in case immunosuppressed patients
INTEG: Rash, urticaria (hives), pruritus, pain or phlebitis at IV site, unusual sweating, alopecia, Stevens-Johnson syndrome
MS: Muscle cramps, Joint pain, leg pain

Nursing considerations

Baseline assessment

• Question for history of allergies, esp. to acyclovir. Evaluate herpes simplex lesions before treatment to compare baseline with treatment effect


• Assess IV site for phlebitis (heat, pain, red streaking over vein). Evaluate
cutaneous lesions
• Ensure adequate ventilation
• Manage chickenpox and
disseminated herpes zoster with strict isolation. Encourage fluid intake

Equipment must be available for anaphylaxis

• Assess for signs of infection, type of lesions, area of body covered, purulent drainage
• Check I&O ratio; report hematuria, oliguria, fatigue, weakness; may indicate nephrotoxicity; check for protein in urine during therapy
• Toxicity: monitor any patient with renal system impairment, as the product is slowly excreted in case of renal system malfunction; toxicity can occur rapidly
• Monitor liver studies: AST, ALT
• Monitor renal tests: urinalysis, protein, BUN, creatinine, CCr; increased BUN, creatinine indicates renal failure and nephrotoxicity
• Monitor bowel pattern before, during treatment; if severe abdominal pain with bleeding occurs, the product should be discontinued
• Evaluate allergies before treatment, reaction of each medication; place allergies on chart in bright red letters; allergic reaction: burning, stinging, swelling, redness, rash, vulvitis, pruritus
• Assess neurologic status in herpes encephalitis


Positive therapeutic result
• Absence of itching, painful lesions
• Crusting and healed lesions

Patient/family teaching

• Teach patient that product may be taken orally before infection occurs or when itching or pain occur, usually before eruptions; that partners need to be told that patient has herpes, they can become infected, so condoms must be worn to prevent reinfections
• Teach patient to report sore throat, fever, fatigue; may indicate superinfection; that product must be taken at equal intervals around the clock to maintain blood levels for duration of therapy
• Teach patient to notify prescriber of side effects: bruising, bleeding, fatigue, malaise; may indicate blood dyscrasias
• Adequate intake of fluids (2 L) to prevent deposits in kidneys, more likely to appear with rapid administration or in dehydration
• Do not touch lesions with bare fingers to avoid spreading infection to new site
• Tell patient to seek dental care during treatment to prevent gingival hyperplasia
• Tell patient to continue therapy for full length of treatment
• Space doses evenly.
• Use finger cot, or rubber glove to apply topical ointment
• Avoid sexual intercourse during duration of lesions to prevent infecting partner.
• Acyclovir does not cure herpes infections
• Tell female patients with genital herpes to have regular Pap smears to prevent undetected cervical cancer

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