Management of severe psoriasis
Topical treatments may not be sufficient for patients with moderate to severe psoriasis and further options include photo- or systemic therapy. Although these treatments are usually prescribed and managed by hospital-based specialists, it is important for all pharmacists to be aware of them and to have an understanding of their implications for patient care. Potential drug-drug interactions, drug-phototherapy interactions and early identification of serious side effects are all issues that need to be considered.
Immunological basis of psoriasis
Psoriasis is now thought to be a disease in which chronic T-cell activation (see Panel 1, p690) by antigen-presenting cells occurs in the skin (ie, it is an immune-mediated disease). Once activated, the T-cells express the inflammatory cytokines TNF-a and interferon- ?. These trigger changes in keratinocyte function and epidermal hyperproliferation as well as a variety of inflammatory responses, including:
- Release of vascular endothelial growth factor (causing angiogenesis and increased vascular permeability)
- Release of further pro-inflammatory cytokines and attraction of neutrophils
The trigger antigen has not yet been identified and new approaches to treatment have focused on drugs that can block T-cell activation, migration or cytokine secretion. The immunological explanation of psoriasis also helps us to understand how the systemic agents might exert their actions.
Some people with psoriasis also have an associated arthropathy. Between 10 and 23per cent develop joint inflammation (psoriatic arthritis).
Phototherapy and photochemotherapy
The beneficial effects of sunlight in psoriasis have been known for centuries. Treatment with artificial UVB radiation was introduced early in the 20th century and this was later followed by PUVA (psoralen plus UVA) in the 1970s. Both UVB and PUVA are thought to modulate the expression of cellular adhesion molecules and induce T-cell apoptosis (programmed cell death). Phototherapy is suitable as first line treatment for patients with extensive, small plaque psoriasis and for those whose disease has failed to respond to topical treatment.
UVB is light of wavelengths 290–320nm. It is the part of the absorption spectrum that is responsible for sunburn. Originally UVB was used in combination with coal tar) but, more recently, it has been used alone. Because UVB burns, the dose (exposure time) has to be adjusted (through a series of tests) to match the skin type of the patient.
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Citation: The Pharmaceutical Journal URI: 10997317
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