Therapeutic Stratification of the Skin

How does a person best organize his or her thinking relative to these different rationales? One can start by asking what the topical drug is supposed to do: Is it to be applied to suppress inflammation; eradicate infectious microorganisms; provide protection from the sun; stop glandular secretions; or provide extended relief from visceral pain? Regardless of which feat the drug is to perform, the answer to the question directs us to where and sometimes how the drug must act to be effective or to a target for the drug. Once knowing the locus of action, one can then consider its accessibility. Clearly, if the drug cannot adequately access its target, little or no therapeutic benefit will be realized.

Sundry drug targets exist on, within, or beneath the skin. These include (i) the skin surface itself (external target); (ยป') the stratum corneum; (iii) any one of several levels of the live epidermis; (iv) the avascular, upper dermis; (v) any one of several deeper regions of the dermis; (vi) one or another of the anatomically distinct domains of the pilosebaceous glands; (vii) eccrine glands; (vi'i'i) apocrine glands; (ix) the local vasculature; and, following systemic absorption, (jc) any of numerous internal tissues. As these targets become increasingly remote, delivery to them becomes sparser, and as a result dilution via tissue distribution and, consequently, adequacy of delivery become less certain. Moreover, the specific properties of these targets and their negotiability are very much determined by the state of health of the skin. Disease and damage alter the barrier characteristics of the skin and therefore target accessibility itself.

Causes of skin damage and/or eruptions are diverse and may alternatively be traced to damage, irritant or allergic reactions, an underlying pathophysiological condition, or an infection. Depending on the problem, the entire skin or only a small part of it may be involved. Moreover, disease may be manifest in one part of a tissue as a consequence of a biochemical abnormality in another. For instance, the cardinal expression of psoriasis is its thickened, silvery, malformed stratum corneum (psoriatic scale), but the disease actually results from maverick proliferation of keratinocytes in the germinal layer of the epidermis. Humankind suffers many skin problems like this, each unique in expression to the well-trained eye. The pharmacist will, from time to time, be called upon to examine an eruption or condition and make recommendation for treatment. If and only if the condition is unmistakable in origin, delimited in area, and of modest intensity, should the pharmacist recommend an over-the-counter (OTC) remedy for its symptomatic relief. Physicians neither need nor want to see inconsequential cuts, abrasions, or mosquito bites, or unremarkable cases of chapped skin, sunburn, or poison ivy eruption, and so on. However, if infection is present and is at all deep seated or if expansive areas of the body are involved, otherwise minor problems can pose a serious threat and physician referral is mandatory. Patients should also be directed to counsel with a physician whenever the origins of a skin problem are in question.

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