Fujisawa laboratories discovered Tacrolimus in 1984. The first publications of experimental data appeared in 1987 and clinical trials started in 1989. Topical Tacrolimus become available for prescription around 1999. Tacrolimus is available as an ointment, an intravenous infusion and in 1mg and 5mg capsules.
The main users of Tacrolimus infusions and capsules are organ transplant patients to prevent organ rejection and people with conditions needing potent immunosuppresion. The ointment comes in two strengths (0.1% & 0.03%) and is available in 30g and 60g tubes. The most important use for Tacrolimus ointment is to treat Atopic Dermatitis, but it has been used for many other skin ailments as well. The 0.1% formulation is better than the 0.03% formulation. The manufacturer recommends the 0.1% ointment for people older than 16 years and the 0.03% ointment for children older than 2 years. Both strengths have however been used successfully in both age groups.
Tacrolimus works by inhibiting the molecule Calcineurin that is essential for activating T-lymphocytes. T- lymphocytes, which are white blood cells, play an active role in Atopic Dermatitis. When T-lymphocytes become activated they help to induce a flare-up of Atopic Eczema. Tacrolimus is most often used as a third line treatment for Atopic Dermatitis.
First line treatment is emollients and second line treatment is topical corticosteroids. Tacrolimus is often prescribed when it is difficult or impossible for eczema-sufferers to wean themselves of topical corticosteroids. The extra immunosuppressive effect of the Tacrolimus should allow most patients to reduce the topical corticosteroids needed to control the dermatitis.
Side effects from using Tacrolimus ointment are mild. About 40% of people using Tacrolimus will experience a burning or stinging sensation where they apply the Tacrolimus. The burning sensation disappears in about 15 minutes. It only occurs in the first week or two and in active patches of dermatitis.
The long-term risks (years) of using Tacrolimus is unclear. The biggest concern about Tacrolimus ointment is that it might raise the risk of developing skin cancers. People using Tacrolimus ointment should limit their exposure to sunlight. In animal studies Tacrolimus accelerated the cancer-forming effects of sunlight. There have a few people that have developed a skin cancer while using Tacrolimus. Nine of these were skin lymphomas. The skin cancers occurred on average 150 days after the start of therapy.
It is unclear if Tacrolimus caused the skin cancers or whether the skin cancers would have developed anyway. Until long-term data becomes available Tacrolimus will probably remain an important third line treatment for eczema-sufferers finding it difficult or impossible to wean themselves of topical corticosteroids.