Home Drug Guide Valacyclovir Hydrochloride

Drug Guide

Generic Name

Valacyclovir Hydrochloride

Brand Names Valtrex

Classification

Therapeutic: Antiviral

Pharmacological: Nucleoside analogue

FDA Approved Indications

Genital herpes simplex virus (HSV) infections
Herpes zoster (shingles)
Varicella (chickenpox)

Mechanism of Action

Valacyclovir is a prodrug that is rapidly converted to acyclovir, which inhibits viral DNA synthesis by acting as a substrate for viral DNA polymerase, thereby preventing viral replication.

Dosage and Administration

Adult: Dosage varies by condition; typically 1 g twice daily for herpes zoster or recurrent genital herpes; 1 g once daily for varicella in immunocompromised patients.

Pediatric: Not approved for children under 18; consult specific guidelines for age-specific dosing.

Geriatric: Adjust dose based on renal function; no specific age-related adjustments otherwise.

Renal Impairment: Reduce dose or increase dosing interval based on creatinine clearance.

Hepatic Impairment: No specific adjustment recommended.

Pharmacokinetics

Absorption: Rapidly absorbed from the gastrointestinal tract (~55% bioavailability).

Distribution: Widely distributed in body tissues; crosses blood-brain barrier.

Metabolism: Converted to active acyclovir in the intestinal wall and liver.

Excretion: Primarily excreted unchanged in urine.

Half Life: Approximately 2.5 to 3.3 hours in patients with normal renal function.

Contraindications

Hypersensitivity to valacyclovir, acyclovir, or any component of the formulation.

Precautions

Renal impairment: adjust dose accordingly.
Immunocompromised patients: monitor for signs of secondary infection.
Pregnancy and lactation: use only if clearly needed; benefits outweigh risks.

Adverse Reactions - Common

Headache (Common)
Nausea (Common)
Vomiting (Common)
Abdominal pain (Common)

Adverse Reactions - Serious

Nephrotoxicity (Rare)
Neurotoxicity (confusion, hallucinations, tremors) (Rare)
Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) (Rare)

Drug-Drug Interactions

Probenecid: may increase acyclovir levels
NSAIDs: increased risk of renal impairment

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor renal function, hydration status, and neurological status during therapy.

Diagnoses:

Risk for impaired renal function
Risk for secondary infections

Implementation: Administer as prescribed; ensure adequate hydration; monitor for adverse effects.

Evaluation: Assess for resolution of symptoms, monitor renal function, and adverse reactions.

Patient/Family Teaching

Take medication exactly as prescribed.
Remain well-hydrated during therapy.
Report any signs of allergic reactions, neurotoxicity, or unusual symptoms immediately.
Use caution if operating machinery until responses are known.

Special Considerations

Black Box Warnings:

Nephrotoxicity and neurotoxicity, especially in patients with renal impairment or dehydration.

Genetic Factors: Not specifically documented.

Lab Test Interference: May increase serum creatinine levels; interpret accordingly.

Overdose Management

Signs/Symptoms: Nausea, vomiting, hallucinations, seizure, coma.

Treatment: Supportive care; consider hemodialysis in severe cases; ensure adequate hydration.

Storage and Handling

Storage: Store at room temperature, 20°C to 25°C (68°F to 77°F). Protect from moisture and light.

Stability: Stable through the expiration date when stored properly.