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Penciclovir Cream – A New Treatment for Herpes Labialis

ABSTRACT

Penciclovir cream (Vectavir™/Denavir™, SmithKline Beecham) is a novel product, approved in 15 countries including the USA and UK, for the treatment of herpes simplex labialis in immunocompetent adults.2 Herpes labialis (cold sores) is a common skin problem, with 20-40% of the population experiencing lesions by the time they are 50 years of age. This viral infection, uncomfortable and cosmetically disfiguring in otherwise healthy individuals, can cause major morbidity in immunocompromised patients.1

Key Words: Herpes Labialis, Penciclovir, cold sores

Efficacy

In clinical studies, penciclovir cream was significantly better than placebo in reducing lesion-associated pain, and in shortening both healing time and the duration of viral shedding.3,4

Two large randomized, multicentre, double-blind, placebo-controlled clinical trials of penciclovir cream have been conducted in patients with a history of frequent herpes labialis. In a US study, 782 patients wer treated with penciclovir cream and 791 with control (vehicle) cream. The median time to lesion resolution in all patients was significantly reduced (p < 0.001) from approximately six days (vehicle) to five days (penciclovir). The median time to loss of pain in the penciclovir treated patients was also significantly reduced (p < 0.001), and penciclovir recipients ceased viral shedding significantly faster than those who received vehicle alone (p = 0.003).3 A second large clinical trial was conducted in Europe and Canada, where 734 patients received penciclovir cream and 750 received vehicle. Penciclovir treated patients healed 29% faster than placebo recipients (p = 0.0001), pain resolved 32% more rapidly (p = 0.0001) and the duration of viral shedding was also significantly shortened.4

Significant benefits on resolution of pain and lesions occurred both in those groups of patients who initiated penciclovir therapy early (prodrome or erythema stage) and those who started it later (papule stage or later).3,4

Side Effects

Topical penciclovir was well tolerated in clinical studies.3,4 Local side effects occurred in 2.5% of treated patients and 4.1% of those who received placebo.5 In a dermal tolerance study, 5% penciclovir cream (a five-fold higher concentration than the commercial formulation) and its vehicle produced less irritancy than acyclovir 5% cream.6

Safety During Pregnancy & Lactation

Penciclovir cream has not been studied in pregnant women. In rats or rabbits, administration of IV penciclovir did not affect the course and outcome of pregnancy. There is no information on whether penciclovir is excreted in human milk following topical administration. However, following oral administration of the penciclovir pro-drug famciclovir to lactating rats, penciclovir was excreted in breast milk.5

Pharmacokinetics

Absorption of penciclovir through the skin seems to be minimal. It was not detected in the plasma or urine of healthy volunteers, following single or repeat application of penciclovir cream, at a dose approximately 67 times that usually used in clinical practice.5 Penciclovir is poorly absorbed orally.7

Mechanism of Action

Penciclovir has potent and selective activity against herpes simplex viruses, acting by inhibiting replication of viral DNA in infected cells6 through the inhibition of viral DNA polymerase.8 Penciclovir is phosphorylated by herpes virus thymidine kinases and cellular enzymes to the active triphosphate form.8

Dosage and Administration

Penciclovir cream is available in a 2g tube containing 1% penciclovir in a 40% propylene glycol/cetomacrogol cream base.3,9 It should be applied topically every two hours during waking hours, for a period of four days. Treatment should commence at the first signs or symptoms (e.g. tingling, swelling) of a recurrence.5,9 Application to mucous membranes is not recommended. The cost of penciclovir cream varies with country, ranging from £4.20 per 2g tube (UK) to $20.58 (USA).

Clinical Assessment

Penciclovir cream is the first antiviral agent to show a consistent effect against herpes labialis, particularly against the pain associated with this condition.3 Although its effects on the time to healing and duration of pain were relatively modest, the product has a role to play in the more rapid alleviation of this uncomfortable disease, and provides clinical benefits whether used during the early or later stages of a herpes labialis outbreak.4,10

“Frequent application of topical penciclovir beginning soon after the onset of herpes labialis can shorten the time to healing by about a day”.11

References

  1. Spruance SL. Herpes simplex labialis. In: Sacks SL, Straus SE, Whitley RJ, Griffiths PD. Clinical management of herpes viruses.Washington DC: IOS Press, 1995: 3-42.
  2. SmithKline Beecham. Personal communication, 9 May 1997.
  3. Spruance SL, Rea TL, Thorning C, et al. Penciclovir cream for the treatment of herpes simplex labialis. JAMA 1997; 277: 1374-1379.
  4. Raborn GW for the Penciclovir Topical Collaborative Study Group. Penciclovir cream for recurrent herpes simplex labialis: an effective new treatment. Paper presented to the 36th Interscience Conference on Antimicrobial Agents and Chemotherapy, 15-28 September 1996, New Orleans, USA.
  5. Denavir™ (penciclovir cream) 1%. US Prescribing Information 1996.
  6. Lavender EA, Laroche JP, MacLennan AI, Amos HE. Dermal tolerance of penciclovir cream compared with placebo and acyclovir cream in healthy volunteers. Paper presented to Clinical Dermatology 2000, May 28-31 1996, Vancouver, BC, Canada.
  7. Vere Hodge RA. Famciclovir and penciclovir. The mode of action of famciclovir including its conversion to penciclovir. Antivir Chem Chemother 1993; 4: 67-84.
  8. Vere Hodge RA, Cheng Y-C. The mode of action of penciclovir. Antivir Chem Chemother 1993; 4 (suppl 1): 13-24.
  9. Vectavir Cold Sore cream. UK Prescribing Information 1996.
  10. Spruance SL for the Penciclovir Topical Collaborative Study Group. Penciclovir cream: a new and effective treatment for recurrent herpes simplex labialis. Paper presented to Clinical Dermatology 2000, May 28-31 1996, Vancouver, BC, Canada.
  11. Topical penciclovir for herpes labialis. The Medical Letter 1997; 39 (June 20): 57-58.

In this issue:

  1. Penciclovir Cream – A New Treatment for Herpes Labialis
  2. Human Skin Equivalent (HSE) , Apligraf® Part II Clinical Use
  3. Medicated Shampoos are Effective in Many Scalp Conditions
  4. Update on Drugs and Drug News - Number 6 1997