Dithranol is widely used in the treatment of psoriasis, but it has the drawbacks of instability, staining of skin and clothes, and irritation, especially of non-involved skin. A polyurethaneurea hydrogel in sheet form has been used to investigate the possibility of developing a drug delivery system that would confine dithranol to the psoriatic plaque, whilst also providing appropriate stability and drug delivery rates. Analytical methods were developed and evaluated, to ensure that dithranol stability could...