eMedExpert Home > Medications Facts > Valacyclovir (Valtrex)

Burroughs Wellcome Co. (now GlaxoSmithKline) developed and investigated several water-soluble esters of acyclovir. One of these was the valine ester of acyclovir which came to be known as "valaciclovir". Burroughs Wellcome patented the invention of valine esters of acyclovir in 1988 3.

Valacyclovir is marketed under the brand name Valtex by GlaxoSmithKline since 1995. It was initially approved by the FDA in June 1995 for the treatment of herpes zoster (shingles). In December 1995 the FDA approved this drug for the treatment of recurrent herpes genitalis and then for the treatment of initial infections of herpes genitalis in October 1996. Maintenance (suppressive) use of valacyclovir for herpes genitalis was approved in September 1997. The use of the drug for herpes labialis was approved in September 2002.

• Herpes zoster (shingles)
• Initial episodes of genital herpes
• Recurrent episodes of genital herpes
• Suppressive therapy of recurrent genital herpes
• Reduction of transmission of genital herpes
• Cold sores (herpes labialis)

• Bell's palsy 4
• Herpes simplex infection prophylaxis 5, 6
• Cytomegalovirus infection and disease after organ transplantation 7, 8
• Retinal necrosis syndrome 13
• Prophylaxis of recurrent genital herpes in late pregnancy 15
• Epstein-Barr virus 17
• Herpes zoster ophthalmicus 16
• Symptoms of schizophrenia 9, 10

• Advantages:
• high efficacy against HSV and VZV infections
• significantly reduces the risk of transmission of genital herpes 2
• decreases asymptomatic shedding of the virus
• more effective than acyclovir for herpes zoster 18
• provide better oral bioavailability than acyclovir 19
• convenient dosage regimen
• favorable safety profile
• considered safe for the mother and baby during pregnancy (so far, no adverse outcomes in the fetus or newborn have been reported)
• minor risk of drug interactions
• Disadvantages:
• risk of renal failure and neurotoxicity 20
• does not eradicate latent virus
• has not been studied in children

Valacyclovir is rapidly and nearly completely converted to acyclovir by intestinal and hepatic metabolism. Acyclovir is converted to acyclovir monophosphate by virus-specific thymidine kinase then further converted to acyclovir triphosphate by other cellular enzymes. Acyclovir triphosphate inhibits DNA synthesis and viral replication by competing with deoxyguanosine triphosphate for viral DNA polymerase and being incorporated into viral DNA.

About 3-5 days.

Valacyclovir has a short half-life about 2.5 to 3.3 hr

• Valacyclovir (Valtrex) versus Other Medications

• 1. Physicians’ Desk Reference, 54th ed. Valtrex (valacyclovir) Prescribing Information. Medical Economics, Thomson Healthcare: Montvale, NJ; 2000.
• 2. Corey L, Wald A , Patel R, Sacks SL, Tyring SK, Warren T, Douglas JM, Paavonen J, Morrow RA , Beutner KR, Stratchounsky LS, Mertz G, Keene ON, Watson HA, Tait D, Vargas-Cortes M. Once-daily valacyclovir to reduce the risk of transmission of genital herpes. N Engl J Med. 2004 Jan 1;350(1):11-20. PubMed
• 3. Therapeutic valine esters of acyclovir and pharmaceutically acceptable salts thereof. US Patent 4,957,924
• 4. Hato N, Yamada H, Kohno H, Matsumoto S, Honda N, Gyo K, Fukuda S, Furuta Y, Ohtani F, Aizawa H, Aoyagi M, Inamura H, Nakashima T, Nakata S, Murakami S, Kiguchi J, Yamano K, Takeda T, Hamada M, Yamakawa K. Valacyclovir and prednisolone treatment for Bell's palsy: a multicenter, randomized, placebo-controlled study. Otol Neurotol. 2007 Apr;28(3):408-13.PubMed
• 5. Gilbert S, McBurney E. Use of valacyclovir for herpes simplex virus-1 (HSV-1) prophylaxis after facial resurfacing: A randomized clinical trial of dosing regimens. Dermatol Surg. 2000 Jan;26(1):50-4. PubMed
• 6. Eisen D, Essell J, Broun ER, Sigmund D, DeVoe M. Clinical utility of oral valacyclovir compared with oral acyclovir for the prevention of herpes simplex virus mucositis following autologous bone marrow transplantation or stem cell rescue therapy. Bone Marrow Transplant. 2003 Jan;31(1):51-5. PubMed
• 7. Egan JJ, Carroll KB, Yonan N, Woodcock A, Crisp A. Valacyclovir prevention of cytomegalovirus reactivation after heart transplantation: a randomized trial. J Heart Lung Transplant. 2002 Apr;21(4):460-6. PubMed
• 8. Lowance D, Neumayer HH, Legendre CM, Squifflet JP, Kovarik J, Brennan PJ, Norman D, Mendez R, Keating MR, Coggon GL, Crisp A, Lee IC. Valacyclovir for the prevention of cytomegalovirus disease after renal transplantation. International Valacyclovir Cytomegalovirus Prophylaxis Transplantation Study Group. N Engl J Med. 1999 May 13;340(19):1462-70. PubMed
• 9. Bechter K. The mild encephalitis-hypothesis--new findings and studies. Psychiatr Prax. 2004 Nov;31 Suppl 1:S41-3. PubMed
• 10. Dickerson FB, Boronow JJ, Stallings CR, Origoni AE, Yolken RH. Reduction of symptoms by valacyclovir in cytomegalovirus-seropositive individuals with schizophrenia. Am J Psychiatry. 2003 Dec;160(12):2234-6. PubMed
• 11. Quan D, Hammack BN, Kittelson J, Gilden DH. Improvement of postherpetic neuralgia after treatment with intravenous acyclovir followed by oral valacyclovir. Arch Neurol. 2006 Jul;63(7):940-2. Epub 2006 May 8. PubMed
• 12. Wu JJ, Brentjens MH, Torres G, Yeung-Yue K, Lee P, Tyring SK. Valacyclovir in the treatment of herpes simplex, herpes zoster, and other viral infections. J Cutan Med Surg. 2003 Sep-Oct;7(5):372-81. Epub 2003 Sep 24. PubMed
• 13. Aizman A, Johnson MW, Elner SG. Treatment of acute retinal necrosis syndrome with oral antiviral medications. Ophthalmology. 2007 Feb;114(2):307-12. Epub 2006 Nov 21. PubMed
• 14. Field HJ, Thackray AM. Early therapy with valaciclovir or famciclovir reduces but does not abrogate herpes simplex virus neuronal latency. Nucleosides Nucleotides Nucleic Acids. 2000 Jan-Feb;19(1-2):461-70. PubMed
• 15. Sheffield JS, Hill JB, Hollier LM, Laibl VR, Roberts SW, Sanchez PJ, Wendel GD Jr. Valacyclovir prophylaxis to prevent recurrent herpes at delivery: a randomized clinical trial. Obstet Gynecol. 2006 Jul;108(1):141-7. PubMed
• 16. Colin J, Prisant O, Cochener B, Lescale O, Rolland B, Hoang-Xuan T. Comparison of the efficacy and safety of valaciclovir and acyclovir for the treatment of herpes zoster ophthalmicus. Ophthalmology. 2000 Aug;107(8):1507-11. PubMed
• 17. Lerner AM, Beqaj SH, Deeter RG, Dworkin HJ, Zervos M, Chang CH, Fitzgerald JT, Goldstein J, O'Neill W. A six-month trial of valacyclovir in the Epstein-Barr virus subset of chronic fatigue syndrome: improvement in left ventricular function. Drugs Today (Barc). 2002 Aug;38(8):549-61. PubMed
• 18. Lin WR, Lin HH, Lee SS, Tsai HC, Huang CK, Wann SR, Chen YS, Chiang SC, Yen MY, Liu YC. Comparative study of the efficacy and safety of valaciclovir versus acyclovir in the treatment of herpes zoster. J Microbiol Immunol Infect. 2001 Jun;34(2):138-42. PubMed
• 19. Bras AP, Sitar DS, Aoki FY. Comparative bioavailability of acyclovir from oral valacyclovir and acyclovir in patients treated for recurrent genital herpes simplex virus infection. Can J Clin Pharmacol. 2001 Winter;8(4):207-11. PubMed
• 20. Carlon R, Possamai C, Corbanese U. Acute renal failure and severe neurotoxicity following valacyclovir. Intensive Care Med. 2005 Nov;31(11):1593. Epub 2005 Sep 20.

Published: March 31, 2008
Last updated: January 07, 2010