| Notes |
- Valaciclovir is the L-valine ester of Acyclovir. It is given
orally as a prodrug which is then converted to acyclovir in the
body. (J549.30.w1)
- Valacyclovir is the L-valyl ester of acyclovir. Available in an oral
formulation, it is converted by hydrolysis in the GIT and liver to
acyclovir. It has 3 - 5 times the oral bioavailability of acyclovir. (J222.340.w1)
- Oral bioavailability is 54%, plasma half-life 2-3 hours.
Intracellular half-life of the triphosphate is 1 - 2 hours (in
vitro data). (J222.340.w1)
- Used as an antiviral drug against herpes simplex and
varicella-zoster viruses. For further information see: Acyclovir
- Adverse effects in humans [as for acyclovir] include:
- Reversible nephropathy due to crystallisation of the drug in
the renal tubules. This normally occurs only after intravenous
administration. It is uncommon and can be managed by giving
fluids at 1 litre per gram of acyclovir, infusing the dose at
a rate of no more than 6 mg/mL, over one hour, and reducing
the dose in individuals with renal insufficiency (as indicated
by creatinine clearance). (J222.340.w1)
- Gastrointestinal disturbance. This is an uncommon direct
effect of the drug and can be managed by reducing the drug
dose if necessary. (J222.340.w1)
- Rash as a rare idiosyncratic reaction. If moderate to
severe, it may be necessary to discontinue the drug. (J222.340.w1)
- Encephalopathy as a rare reaction precipitated by renal
failure or by other drugs with adverse effects on the CNS.
Treated by discontinuing use of the drug. (J222.340.w1)
- Thrombotic microangiopathy as a rare complication of unknown
cause. It occurs only in immunocompromised individuals being
given multiple drugs. Management involves discontinuing the
drug. (J222.340.w1)
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