Valaciclovir

Valaciclovir is the L-valyl ester prodrug of aciclovir, offering significantly better oral bioavailability (approximately 55% versus 15 to 20% for aciclovir). This allows less frequent dosing while achieving higher blood levels. Once absorbed, valaciclovir is rapidly and almost completely converted to aciclovir, which inhibits viral DNA polymerase in herpes simplex (HSV) and varicella-zoster (VZV) infections. It is used for the treatment of genital herpes, cold sores, herpes zoster (shingles), and suppressive therapy to reduce HSV recurrences and transmission.

How to Take Valaciclovir

Take valaciclovir with plenty of water, with or without food. Start treatment as early as possible after symptoms begin. For cold sores and genital herpes, this means starting within the first 24 hours of noticing tingling or blistering. For shingles, starting within 72 hours of the rash first appearing gives the best results.

For genital herpes episodes, the usual course is 1 g twice daily for five days. For suppressive therapy to reduce the frequency of outbreaks, 500 mg once daily is taken continuously. For cold sores, a short two-day course works well when started at the very first sign of an outbreak.

Genital herpes (first episode): 500 mg twice daily for 5 to 10 days. Recurrent episodes: 500 mg twice daily for 3 to 5 days. Suppression: 500 mg once daily. Herpes zoster: 1 g three times daily for 7 days.

Common Side Effects

Common side effects include:

• Headache
• Nausea
• Stomach discomfort
• Dizziness

These are generally mild and resolve on their own. At high doses, or in people with existing kidney problems, valaciclovir can affect kidney function. Staying well hydrated helps reduce this risk. In rare cases, neurological effects such as confusion or agitation can occur. Seek medical attention straight away if these develop.

Maintain adequate hydration, especially in renal impairment, to prevent crystallisation of aciclovir in the kidneys. Dose reduction is required in renal impairment.

Contraindicated in known hypersensitivity to valaciclovir, aciclovir, or any excipient.