Imiquimod is a an immune response modifier. It is manufactured as a 5% cream called Aldara™. A 3.75% cream called Zyclara™ has also been approved by the FDA in the USA, but is not yet available in New Zealand (June 2013). Imiquimod is mainly used to treat genital warts, actinic keratoses and basal cell skin cancers.
Imiquimod works by stimulating the immune system to release a number of chemicals called cytokines, which are important in fighting viruses and destroying cancer cells.
When used to treat skin cancers and pre-cancerous lesions it results in inflammation, which destroys the lesion. The degree of inflammation is quite variable from person to person, in part due to the type of skin lesion and in part due to genetic factors. The imiquimod is taken up by the so-called ‘toll-like receptor 7’ on certain immune cells that are found in the outside part of the skin (the epidermis); these receptors are expressed more in some individuals and in some skin lesions than in others.
Imiquimod is particularly useful on areas where surgery or other treatments may be difficult, complicated or otherwise undesirable, especially the face and lower legs.
A course of treatment ranges from 4 to 16 weeks. Before starting, a biopsy may be performed to confirm the diagnosis. Treatment should be carefully monitored, because the cream may need to be applied more or less frequently than originally planned or for a shorter or longer course, depending on response. Once the inflammation has settled there is generally a good or excellent cosmetic result with little scarring.
Imiquimod is particularly useful for:
- Actinic keratoses (also called actinic keratoses or SKs).
- Basal cell carcinoma (BCC), especially superficial types
- Bowen disease, also known as in-situ squamous cell carcinoma (SCC), an unregistered indication at this time (June 2014)
It is also used to treat viral infections, especially genital warts. It may also be helpful in the treatment of common warts (once they have been thinned down by other means), plane warts, and herpes simplex. Experimentally it has been successful in reducing some keloid scars, granuloma annulare, vitiligo, melanoma in situ and, in combination with diphencyprone, metastatic melanoma (see topical and intralesional immunotherapy for melanoma.
Although sometimes prescribed for molluscum contagiosum, clinical trials have not shown imiquimod to be of benefit.
Treatment regimes for imiquimod
Various imiquimod treatment regimes are used. For example:
- Actinic keratoses: imiquimod is used twice weekly for six weeks, repeated if necessary after a break of four weeks. Very scaly lesions should be frozen with liquid nitrogen about three weeks before starting imiquimod.
- Basal cell carcinomas and Bowen's disease: imiquimod is used five times weekly for six weeks.
- Genital warts: imiquimod is used three times weekly; or, if available, 3.75% cream daily; until total clearance or for up to 8 weeks.
Apply the imiquimod less often if the reaction is excessive, and more often if no reaction occurs. Check with your doctor; he or she may recommend a different regime in your case. Treatment is sometimes continued for up to 16 weeks.
How to use imiquimod cream
Wash your hands before and after applying imiquimod cream.
Cut the top off the sachet or pierce the sachet with a needle and squeeze out a tiny amount of cream onto your fingertip. Apply this to the affected areas.
Although the information on the packet states that the sachet is for single use, you could seal it using a paper clip or tape and store in a closed container to prevent the cream drying out.
What to expect from imiquimod cream
Areas treated with imiquimod will be come inflamed. The effects include itching, burning, redness, ulceration (sores), scabbing, flaking and pain. These reactions indicate that the cream is likely to be effective - if there is no inflammation, imiquimod is unlikely to clear the lesions. An exaggerated response may clear the skin lesion sooner than expected - sometimes after as few as three or four applications. In some patients, surrounding untreated areas also become inflamed but this will settle when treatment is discontinued.
If you develop a severe reaction with black scabs and ulceration, stop applying the cream and arrange to see your doctor as soon as possible.
BCC prior to treatment
BCC: During treatment
BCC: After treatment
SKs: Mild reaction
SKs: Moderate reaction
BCC: Severe reaction
More images of the effect of imiquimod ...
Systemic side effects from imiquimod cream
When using imiquimod cream, 'flu-like symptoms may develop, such as fever, fatigue, headache, nausea, diarrhoea and muscle pain. These are generally mild and may be treated with paracetamol. However, if they are troublesome, stop applying imiquimod cream and contact your doctor. Side effects should resolve within a few days of stopping treatment. They may also resolve with continuing treatment.
Make sure you have made an appointment for follow-up with your doctor.
- Dahl MV. Imiquimod: An immune response modifier. J Am Acad Dermatol 2000; 43: S1-5. Medline
- Sauder DN. Immunomodulatory and pharmacologic properties of imiquimod. J Am Acad Dermatol 2000; 43: S6-11. Medline
- Edwards L. Imiquimod in clinical practice. J Am Acad Dermatol 2000; 43: S12-17. Medline
- Edwards L, Ferenczy A, Eron L, et al. Self-administered topical 5% imiquimod cream for external anogenital warts. Arch Dermatol 1998; 134: 25-30. Medline
- Beutner KR, Geisse JK, Helman D, et al. Therapeutic response of basal cell carcinoma to the immune response modifier imiquimod 5% cream. J Am Acad Dermatol 1999; 41: 1002-7. Medline
- Mackenzie-Wood A, de Launey J, Kossard S, et al. Safety and efficacy of imiquimod 5% cream for the treatment of Bowen's disease. J Invest Dermatol 1998; 110: 684 (abstract only).
- Syed TA, Goswami J, Ahmadpour OA, et al. Treatment of molluscum contagiosum in males with an analog of imiquimod 1% in cream: A placebo-controlled, double blind study. J Dermatol 1998; 25: 309-13. Medline
On DermNet NZ:
- Consumer medicine information and data sheets – Medsafe
- Drugs, Herbs and Supplements – MedlinePlus
- Imiquimod cream – British Association of Dermatologists
Books about skin diseases:
See the DermNet NZ bookstore
The New Zealand approved datasheet is the official source of information for this prescription medicine, including approved uses and risk information. Check the New Zealand datasheet on the Medsafe website.