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Letter to the editor

Editor, – The two recent articles on antiviral drugs were excellent - 'Antiviral drugs - mechanisms of action' by S. Locarnini (Aust Prescr 1993;16:78-81)and 'Antiviral drugs - clinical applications' by A.C. Street(Aust Prescr 1993;16:81-6). However, I felt that Dr Street's judgement that topical acyclovir (5% aqueous cream - which is unavailable in Australia) for orolabial and genital herpes simplex virus (HSV) infections had no clinical efficacy was a little harsh. I agree that it seems that the benefit of topical acyclovir for orolabial and recurrent genital HSV infections in immuno competent patients is limited to a reduction in viral shedding. However, topical acyclovir may have a role in primary genital herpes in immuno competent hosts. It reduces the duration of the lesions, but has minimal efficacy in reducing new vesicle formation.1,2

In immuno compromised patients with mucocutaneous HSV disease, topical therapy also results in a significant reduction in the period of pain and healing of lesions.3,4

Topical therapy may have an effective clinical application in the management of primary genital HSV infection, and minor mucocutaneous HSV infections in immuno compromised patients.5

Len Moaven
Virology Registrar
ICPMR
Westmead Hospital
Westmead, N.S.W.

Author's comments

Dr A. Street, the author of the article, comments:
There are two topical acyclovir preparations. The 3% acyclovir ointment isused for the treatment of herpetic conjunctivitis and keratitis. A 5% preparation, formulated as an ointment or aqueous cream, is available in the U.S.A. and Europe, but not in Australia.

Although topical5% acyclovir provides some clinical benefit for patients with primary genital herpes, oral acyclovir is significantly more effective and is the treatment of choice.6 Topical acyclovir is ineffective for recurrent genital herpes.7

Dr Moaven also notes that topical acyclovir has been reported to be effective in immuno compromised patients with limited mucocutaneous disease. However, since oral therapy is superior to topical therapy in immuno competent individuals, it seems unwise to rely on topical treatment for a group of patients in whom herpetic infections are generally more severe and frequent.

The available evidence shows that topical acyclovir is less effective than systemic therapy and thus has little clinical role at present, except for treatment of herpes simplex eye infections.

References

  1. Fiddian AP, Kinghorn GR, Goldmeier D, Rees E, Rodin P, Thin RN, et al. Topical acyclovir in the treatment of genital herpes: a comparison with systemic therapy. J Antimicrob Chemother 1983;12 (B Suppl):67S-77S.
  2. Corey L, Nahmias AJ, Guinan ME, Benedetti JK, Critchlow CW, Holmes KK. Atrial of topical acyclovir in genital herpes simplex virus infections. N Engl J Med 1982;306:1313-9.
  3. Whitley R, Barton N, Collins E, et al. Mucocutaneous herpes simplex virus infections in immuno compromised patients: a model for evaluation of topical antiviral agents. Am J Med 1982; 73:236-40.
  4. Whitley RJ, Levin M, Barton N, Hershey BJ, Davis G, Keeney RE, et al. Infections caused by herpes simplex virus in the immuno compromised host: natural history and topical acyclovir therapy. J Infect Dis 1984;150:323-9.
  5. Whitley RJ, Gnann JW Jr. Acyclovir: a decade later. N Engl J Med 1992;327:782-9.
  6. Corey L, Benedetti J, Critchlow C, Mertz G, Douglas J, Fife K, et al. Treatment of primary first episode genital herpes simplex virus infections with acyclovir: results of topical, intravenous and topical therapy. J Antimicrob Chemother1983;12 (B Suppl):79S-88S.
  7. Luby JP, Gnann JW Jr, Alexander WJ, Hatcher VA, Friedman-Kien AE, Klein RJ, et al. A collaborative study of patient-initiated treatment of recurrent genital herpes with topical acyclovir or placebo. J Infect Dis 1984;150:1-6.