The skin

33 The skin





Questions



image What is the pathology of acne, psoriasis and dermatitis?

image What drugs are used in the treatment of these diseases?

The skin is an important barrier to the external environment, a sensory organ (touch, heat, cold) and regulates body temperature (sweating). Non-allergic and allergic inflammatory conditions lead to disruption in this function and are a common cause of morbidity (e.g. acne, psoriasis, dermatitis). By its very nature, the skin is amenable to topical application of pharmacological agents (e.g. ointments, pastes, lotions and creams).



Acne


Acne is a condition of the hair follicles involving excessive sebum production, bacterial infection (Propionibacterium acnes), desquamation of follicular epithelium and inflammation (Fig. 3.33.1A). A number of topical treatments are available.


image image

Fig. 3.33.1 Skin disorders. (A) Severe acne; (B) psoriasis; (C) dermatitis.




Benzoyl peroxide


This is a frequently used first-line therapy and has strong antibacterial activity, reducing colonization by P. acnes. Benzoyl peroxide causes drying and skin irritation and contact allergy may develop in susceptible individuals.



Salicylic acid


This is a keratolytic agent that breaks down follicular plugs and the rate of follicular desquamation, thereby reducing the number of comedones. It may exacerbate inflammatory acne lesions through erythema and peeling.



Azelaic acid


This naturally occurring dicarboxylic acid inhibits DNA synthesis in keratinocytes and is reported to have a comedolytic activity. It is mildly irritating and can cause skin lightening in dark-skinned individuals.



Topical antibiotics


Antibiotics are used to reduce the number of bacteria in the pilosebaceous duct and have a mild comedolytic effect. They are administered orally in patients with severe acne or when topical therapy fails. Examples of antibiotics used for the treatment of acne include the tetracyclines (tetracycline, minocycline, doxycycline, lymecycline), erythromycin, clindamycin and cotrimoxazole. Side-effects from oral administration include gastrointestinal disturbances, vaginal candidiasis, pseudomembranous colitis, sensitization of skin to sunlight and bacterial resistance.

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Jul 18, 2016 | Posted by in PHARMACY | Comments Off on The skin

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