Editor, – Imiquimod 5% cream (Aldara) is available in single use 250 mg sachets for genital warts and basal cell carcinoma. For some years, doctors have been prescribing imiquimod ‘off-label’ for the treatment of molluscum contagiosum in children. Because of the cost ($150–200 for 12 sachets) it is usually prescribed as compounded imiquimod 0.1% cream. To make this, one sachet of imiquimod 5% cream can be diluted 50-fold to 12.5 g of 0.1% cream.
I have seen four children who had been prescribed imiquimod 0.1% which was compounded incorrectly by three separate pharmacies. Each pharmacist had incorrectly assumed that the label ‘250 mg’ on the packaging refers to the quantity of the active ingredient – imiquimod – in the sachet. In fact, it refers to the quantity of 5% cream.
As each dispensed jar of cream is labelled ‘imiquimod 0.1%’, clinicians need a high index of suspicion to detect this error. They will need to confirm with the patient how much cream was given and what it cost. For example, if a patient received a 250 g jar of ‘0.1% cream’ for $49.95 (as in one of my cases), it is clear an error has been made as this would otherwise contain several hundred dollars worth of imiquimod.
Some months after it began being routinely used for molluscum treatment in Melbourne, imiquimod 0.1% was described to me as ‘working well’ and ‘effective’ in many children. To my knowledge, all those children had received their compounded cream from one pharmacy and the dilution was incorrect. As such they had only received imiquimod 0.005%, a 1 in 1000 dilution of the commercially available product. It is unlikely that this was effective and illustrates the difficulty of assessing treatments for molluscum. Molluscum lesions often flare (and hence present to the doctor) shortly before complete resolution so that clearing after presentation is common whatever treatment is used.
Rod Phillips
Paediatric skin specialist
Royal Children’s Hospital
Melbourne
