Acyclovir: Uses, Action, Routes, Dosage, and side effects by Nurses note

 ACYCLOVIR

Pharmacotherapeutic: Synthetic nucleoside

Clinical : Antiviral 

Uses

Parenteral

Treatment of initial and prophylaxis of recurrent mucosal and cutaneous herpes simplex virus (HSV-1 and HSV-2 ) in immunocompromised patients. Treatment of severe initial episodes of herpes genitalis in immunocompetent patients. Treatment of herpes simplex encephalitis including neonatal herpes simplex virus. Treatment of herpes zoster (shingles) in immunocompromised patients. 

Oral

Treatment of initial episodes and prophylaxis of recurrent herpes simplex (HSV 2 genital herpes ). Treatment of chickenpox (vericella). Acute treatment of herpes zoster (shingles)

OFF-LABEL: (parenteral/Oral): prevention of HSV reactivation in HIV positive patients ; hematopoietic stem cell transplant (HSCT); during periods of neutropenia in patients with cancer; prevention of VZV reactivation in allogenic HSCT; treatment of disseminated HSC or VZV in immunocompromised patients with cancer; empiric treatment of suspected encephalitis in immunocompromised patients with cancer; treatment of initial and prophylaxis of recurrent mucosal and cutaneous herpes simplex infection in immunocompromised patients. 

Topical

Cream: Treatment of recurrent herpes labialis (cold sores) in immunocompetent patients. 

Ointment: Management of initial genital  herpes. Treatment of mucocutaneous HSV in immunocompromised patients. 

Precautions 

Contraindications: Use in neonates when acyclovir is reconstituted with bacteriostatic water for injection containing benzyl alcohol. Hypersensitivity to acyclovir, valacyclovir. 

Cautions: Immunocompromised patients (thrombocytopenic purpura/hemolytic uremic syndrome reported ); elderly, renal impairment, use of other nephrotoxic medications. 

IV Use: patients  with underlying neurologic abnormalities, serious hepatic/electrolyte abnormalities, substantial hypoxia. 

Action

Converts to acyclovir triphosphate, which competes for viral DNA polymerase, becoming part of DNA chain. 

Therapeutic Effect: Interferes with DNA synthesis and viral replication. Virustatic.

Pharmacokinetics

15%-30% absorbed from GI tract. Bioavailability: 10-20%; minimal absorption following topical application. Protein binding: 9%-36%. Widely distributed. Partially metabolized in liver. Excreted primarily in urine. 

Half-life: 2.5 hrs (increased in renal impairment ).

Lifespan considerations

Pregnancy/Lactation : Crosses placenta; distributed in breast milk. Children : Safety and efficiency not established in patients younger than 2 yrs (younger than 1yr for IV use). Elderly: Age-related renal impairment may require decreased dosage. May experience more neurologic effects (e.g. agitation, confusion, hallucinations ).

Administration 

IV

Reconstitution

• Add 10 mL sterile water for injection to each 500-mg vial (50 mg/mL). Do not use Bacteriostatic water for injection containing benzyl alcohol or parabens ( will cause precipitate)
• Shake well until solution is clear.

Further dilute with at least 100 mL D5W or NaCl. Final concentration should be 7 mg/mL or less. ( concentration greater than 10 mg/mLmL increase risk of phlebitis )
Rate of Administration 

• Infuse over at least 1 hr (nephrotoxicity due to crystalluria and renal tubular damage may occur with too-rapid rate).
• Maintain adequate hydration during infusion and for 2 hrs following IV administration. 

Storage 

• Store vials at room temperature. 
• Solutions of 50 mg/dl stable for 12 hrs at room temperature ; may form precipitate if refrigerated. 
• IV infusion (piggyback ) stable for 24 hrs at room temperature. 

PO

• May give without regard to food. 
• Do not crush /break capsules. 
• Store capsules at room temperature. 

Topical 

(Ointment )

• Avoid contact with eye.
• Use finger cot/rubber gloves to prevent autoinoculation. 

(Cream)

• Apply to cover only cold sores or area with symptoms. 
• Rub until it disappears. 

Indications/routes/dosage

Genital Herpes (initial Episode)

IV: Adults, Elderly: 5-10 mg/kg q8h for 2-7 days. Followed with oral therapy to complete at least 10 days of therapy.

PO: Adults, Elderly, Children, 12 yrs and older: 200 mg q4h 5 times /day for 10 days or 400 mg 3 times/day for 7-10 days. Children younger than 12 yrs: 40-80 mg/kg/day in 3-4 divided doses for 5-10 days. Maximum: 1200 mg/day.

Topical adults: (ointment )  1/2 inch for 4 inch squre surface q3h (6 times/day) for 7 days.

Genital Herpes ( recurrent )

Intermittent therapy 

PO: Adults, Elderly, Children 12 yrs and older: 200 mg q4h 5 time/day for 5 days or 400 mg 3 times/day for 5-10 days or 800 mg 2 times/day for 5 days or 800 mg 3 times/day for 2 days.

Children younger than 12 yrs: 20 mg/kg 3 times/day for 5 days.  Maximum : 400 mg/dose.

Herpes Zoster (Shingles )

IV: Adults, Children 12 yrs and older (immunocompromised ) 10 mg/kg/dose q8h for 7-10 days.  Children younger than 12 yrs: (immunocompromised ) 10 mg/kg/dose q8h for 7-10 days. 

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

Herpes Labialis ( cold sores)

Topical: Adults, Elderly, Children 12 yrs and older: Apply to affected area 5 times/day for 4 days.  

Buccal Tablet: 50 mg as a single dose to upper gum region. 

Varicella- Zoster ( Chickenpox )

Begin treatment within 24 hrs onset of rash. 

PO: Adults, Elderly, Children older than 12 yrs and Children  2-12 yrs, weighing 40 kg or more: 800 mg 4 times/day for 5 days. Children 2-12 yrs, weighing less than 40 kg: 20 mg/kg 4 times/day for 5 days. Maximum : 800 mg/dose. 

Usual Neonatal dosage 

HSV (treatment) (IV): 20 mg/kg/dose q8-12h for 14-21 days. 

HSV (chronic suppression ) (PO): 300 mg/m2/dose q8 following IV therapy for 6months.

Varicella Zoster (IV) : 10 mg/kg/dose q8h for 5-10 days.

Adverse effects 

Rapid parenteral administration, excessively high doses, or fluid and electrolyte imbalance may produce renal failure. Toxicity not reported with oral or topical use. 

Nursing Considerations

Baseline assessment 

Question for history of allergies, especially to acyclovir. Assess herpes simplex lesions before treatment to compare baseline with treatment effect. 

Intervention / evaluation 

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