Acyclovir (Zovirax) versus ...

• Acyclovir vs Valacyclovir
• Acyclovir vs Erythromycin
• Acyclovir vs Brivudin
• Acyclovir vs Famciclovir
• Acyclovir vs Penciclovir

Based on "Antibiotic and Chemotherapy"
written by Roger G. Finch

Pityriasis Rosea

Acyclovir is more effective than erythromycin in reducing the severity and duration of pityriasis rosea.

The randomized study 1 compared the effectiveness of oral erythromycin and oral acyclovir in the treatment of Pityriasis rosea. One study group was given high-dose oral Acyclovir and another group oral Erythromycin in standard dose. After eight weeks all patients achieved complete response in both the groups. The response to Acyclovir compared with that to Erythromycin was better and was statistically significant.

Brivudin (bromovinyl deoxyuridine) is a nucleoside analogue with a high and selective antiviral activity against varicella-zoster virus (VZV) and herpes simplex virus type 1 (HSV-1). Brivudin has a markedly higher anti-VZV potency than oral acyclovir. Brivudin has no nephrotoxic properties, which is an advantage when compared to acyclovir.

Herpes Zoster
Brivudin significantly more effective than acyclovir in terminating vesicle formation in herpes zoster3. Both treatments are equally effective in the time to full crusting of lesions and time to loss of crusts.

In a double-blind survey study2 the incidence of zoster-associated pain occurring or persisting after rash healing was significantly lower in brivudin recipients (32.7%) than in acyclovir recipients (43.5%). Mean duration of postherpetic neuralgia was similar with brivudin (173 days) and acyclovir (164 days).

Acyclovir is a more potent inhibitor of viral DNA polymerase than famciclovir 7. Famciclovir is less potent because it does not cause chain termination of viral DNA. However, famciclovir achieves higher intracellular concentrations for longer periods of time than acyclovir, and as a result has a prolonged antiviral effect.

Famciclovir is more bioavailable than acyclovir (77% versus 30%) and has a longer intracellular half-life which allows for a twice daily dosing. So famciclovir is more convenient because it requires less frequent dosing.

However, high cost of famciclovir may override its convenience when choosing between two medications that have comparable efficacy.

Herpes zoster

Acyclovir and famciclovir have comparable efficacy and similar safety profile.

In the clinical study there was no significant differences between the four treatment regimens (famciclovir 750 mg once daily, 500 mg twice daily and 250 mg daily, and acyclovir 800 mg five times daily) with respect to times to full crusting; loss of vesicles, ulcers and crusts; cessation of new lesion formation; a 50% reduction in the area of affected skin; and the loss of acute pain. 6
The pharmacokinetics of famciclovir allows a more convenient dosing schedule than the schedule used with acyclovir.

Bell's palsy

Famciclovir is superior to acyclovir in the treatment of severe facial palsy 8. For moderate palsy acyclovir and famcyclovir provide comparable improvement.

Penciclovir has a mechanism of action similar to that of acyclovir. Penciclovir triphosphate acts as a competitive inhibitor of viral DNA polymerase, but unlike acyclovir, it does not cause chain termination.

Herpes labialis (cold sores)

In comparative model the efficacy of penciclovir cream was greater than acyclovir cream. 5

Genital herpes

The results of the study showed that there are no significant differences in clinical efficacy between penciclovir 1% cream and acyclovir 3% cream with respect to clinical cure rate, times to healing, resolution of all symptoms, absence of blisters, cessation of new blisters, crusting, and loss of crust. However a significantly shorter time to crusting was found with penciclovir when compared with acyclovir. Adverse experience was comparable with two medications. 4

• Acyclovir (Zovirax) Facts

• 1. Amatya A, Rajouria EA, Karn DK. Comparative study of effectiveness of oral acyclovir with oral erythromycin in the treatment of Pityriasis rosea. Kathmandu Univ Med J (KUMJ). 2012 PubMed
• 2. Wassilew SW, Wutzler P; Brivddin Herpes Zoster Study Group. Oral brivudin in comparison with acyclovir for herpes zoster: a survey study on postherpetic neuralgia. Antiviral Res. 2003 Jun;59(1):57-60.
• 3. Wassilew SW, Wutzler P; Brivddin Herpes Zoster Study Group. Oral brivudin in comparison with acyclovir for improved therapy of herpes zoster in immunocompetent patients: results of a randomized, double-blind, multicentered study. Antiviral Res. 2003 Jun;59(1):49-56.
• 4. Chen XS, Han GZ, Guo ZP, Lu NZ, Chen J, Wang JB; Penciclovir Multicenter Genital Herpes Clinical Study Group. A comparison of topical application of penciclovir 1% cream with acyclovir 3% cream for treatment of genital herpes: a randomized, double-blind, multicentre trial. Int J STD AIDS. 2000 Sep;11(9):568-73. PubMed
• 5. McKeough MB, Spruance SL. Comparison of new topical treatments for herpes labialis: efficacy of penciclovir cream, acyclovir cream, and n-docosanol cream against experimental cutaneous herpes simplex virus type 1 infection. Arch Dermatol. 2001 Sep;137(9):1153-8. PubMed
• 6. Shafran SD, Tyring SK, Ashton R, Decroix J, Forszpaniak C, Wade A, Paulet C, Candaele D. Once, twice, or three times daily famciclovir compared with aciclovir for the oral treatment of herpes zoster in immunocompetent adults: a randomized, multicenter, double-blind clinical trial. J Clin Virol. 2004 Apr;29(4):248-53.
• 7. Tuttle JV, Krenitsky TA. Effects of acyclovir and its metabolites on purine nucleoside phosphorylase. J Biol Chem. 1984 Apr 10;259(7):4065-9. PubMed
• 8. Kim HJ, Kim SH, Jung J, et al. Comparison of acyclovir and famciclovir for the treatment of Bell's palsy. Eur Arch Otorhinolaryngol. 2016 Oct;273(10):3083-90. PubMed

Published: March 31, 2008
Last reviewed: February 09, 2017