GSL: General Sales List
This information is intended for use by health professionals
Adults (including older people) and children over 12 years of ageFenistil Cold Sore Cream should be applied at approximately two hourly intervals during waking hours, (approximately 8 times a day). Treatment should be continued for 4 days. If the condition gets worse or does not improve after 4 days treatment, seek medical advice.Treatment should be started as early as possible after the first sign of an infection. Paediatric populationChildren (under 12 years):The safety and efficacy of Fenistil Cold Sore Cream in children below 12 years of age have not been established.No data are available.
PregnancyThere is unlikely to be any cause for concern regarding adverse effects when the cream is used in pregnant women as systemic absorption of penciclovir following topical administration of Fenistil Cold Sore Cream has been shown to be minimal (see Section 5.2).Since the safety of penciclovir in human pregnancy has not been established, Fenistil Cold Sore Cream should only be used during pregnancy or in nursing mothers on the advice of a doctor, if the potential benefits are considered to outweigh the potential risks associated with treatment.
LactationThere is unlikely to be any cause for concern regarding adverse effects when the cream is used in lactating women as systemic absorption of penciclovir following topical administration of Fenistil Cold Sore Cream has been shown to be minimal (see Section 5.2).There is no information on excretion of penciclovir in human milk.
Summary of the safety profileFenistil Cold Sore Cream has been well-tolerated in human studies. Clinical trial experience has shown that there was no difference between Fenistil Cold Sore Cream and placebo in the rate or type of adverse reactions reported.The most common events are application site adverse events.
Tabulated list of adverse reactionsAdverse reactions are listed below by system organ class and frequency. Frequencies are defined as: very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1,000 to <1/100); rare (≥1/10,000 to <1/1,000); very rare (<1/10,000); unknown (cannot be estimated from available data). Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness.
|General disorders and administration site condition: Common||Application site reactions (including skin burning sensation, pain of skin, hypoaesthesia)|
|Immune System disorders: Not known||hypersensitivity, urticarial|
|Skin and subcutaneous disorders: Not known||dermatitis allergic (including rash, pruritus, blisters and oedema)|
Reporting of suspected adverse reactionsReporting suspected adverse reactions after authorization of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme Website: www.mhra.gov.uk/yellowcard.
Mechanism of actionPenciclovir has demonstrated in vivo and in vitro activity against herpes simplex viruses (types 1 and 2) and varicella zoster virus. In virus-infected cells penciclovir is rapidly and efficiently converted into a triphosphate (mediated via virus-induced thymidine kinase).Penciclovir triphosphate persists in infected cells for more than 12 hours where it inhibits replication of viral DNA and has a half-life of 9, 10 and 20 hours in cells infected with varicella zoster virus, herpes simplex virus type 1 and herpes simplex virus type 2 respectively. In uninfected cells treated with penciclovir, concentrations of penciclovir triphosphate are only barely detectable. Accordingly, uninfected cells are unlikely to be affected by therapeutic concentrations of penciclovir.
Clinical efficacy and safetyIn clinical studies, Fenistil treated patients healed 30% faster than placebo (up to one day earlier), pain resolution was 25-30% faster (median improvement of up to one day) and infectivity resolved up to 40% faster (one day earlier) than placebo.
General characteristicsFollowing application of Fenistil Cold Sore Cream in a human volunteer study at a daily dose of 180mg penciclovir (approximately 67 times the proposed daily clinical dose), to occluded and abraded skin for 4 days, penciclovir was not quantifiable in plasma and urine.
General toxicologyTopical application of 5% Fenistil Cold Sore Cream for 4 weeks to rats and rabbits was well tolerated. There was no evidence of contact sensitisation in guinea pigs.A full programme of studies has been completed using intravenous penciclovir. These studies did not raise any safety concerns regarding topical use of Fenistil Cold Sore Cream. There is a minimal systemic absorption of penciclovir following topical administration.
Genotoxicity and Reproductive toxicityAnimal studies have not shown any embryotoxic or teratogenic effects with penciclovir given intravenously (at doses greater than 1200 times those recommended for clinical use via topical application), nor were there any effects on male and female fertility and general reproductive performance (at doses greater than 1600 times those recommended for clinical use via topical application). Studies in rats show that penciclovir is excreted in the breast milk of lactating females given oral famciclovir (famciclovir; the oral form of penciclovir, is converted in vivo to penciclovir).The results of a wide range of mutagenicity studies in vitro and in vivo indicates that penciclovir does not pose a genotoxic risk to man.