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Action/Kinetics:
Rapidly converted to acyclovir, which has inhibitory activity against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) and varicella-zoster virus. Acts by inhibiting replication of viral DNA by competitive inhibition of viral DNA polymerase, incorporation and termination of the growing viral DNA chain, and inactivation of the viral DNA polymerase. Rapidly absorbed after PO administration and is rapidly and nearly completely converted to acyclovir and l-valine by first-pass intestinal or hepatic metabolism.
Time to peak levels: Approximately 1.5 hr.
Peak plasma levels: Less than 0.5 mcg/mL of valacyclovir at all doses.
t
1/2, acyclovir: 2.5-3.3 hr. Approximately 50% is excreted through the urine.
Uses:
Treatment of recurrent episodes of genital herpes in immunocompetent adults. Treatment of herpes zoster in immunocompetent adults. Suppression of genital herpes in adults who have experienced previous outbreaks.
Contraindications:
Hypersensitivity or intolerance to acyclovir or valacyclovir. Use in immunocompromised individuals. Lactation.
Special Concerns:
Use with caution in renal impairment or in those taking potentially nephrotoxic drugs. Dosage reduction may be necessary in geriatric clients depending on the renal status. Safety and efficacy have not been determined in children.
Side Effects:
GI: N&V;, diarrhea, constipation, abdominal pain, anorexia.
CNS: Headache, dizziness.
Miscellaneous: Asthenia, precipitation of acyclovir in renal tubules resulting in acute renal failure and anuria.
Overdose Management:
Symptoms: Precipitation of acyclovir in renal tubules if the solubility (2.5 mg/mL) is exceeded in the intratubular fluid.
Treatment: Hemodialysis until renal function is restored. About 33% of acyclovir in the body is removed during a 4-hr hemodialysis session.
Drug Interactions:
Administration of cimetidine and/or probenecid decreased the rate, but not the extent, of conversion of valacyclovir to acyclovir. Also, the renal clearance of acyclovir was decreased.
How Supplied:
Tablet: 500 mg, 1 g
Dosage
?Tablets
Herpes zoster (shingles).
Adults: 1 g t.i.d. for 7 days.
Dosage with renal impairment: C
CR, 30-49 mL/min: 1 g q 12 hr; C
CR, 10-29 mL/min: 1 g q 24 hr; and, C
CR, less than 10 mL/min: 500 mg q 24 hr.
Recurrent genital herpes.
Adults: 500 mg b.i.d. for 5 days.
Dosage with renal impairment: C
CR, 30-49 mL/min: 500 mg q 12 hr; C
CR, 10-29 mL/min: 500 mg q 24 hr; and, C
CR, less than 10 mL/min: 500 mg q 24 hr.
Suppression of genital herpes.
Adults: 1 g once daily (500 mg once daily for those who have 9 or fewer recurrences per year).
