If the drug must be continued, clinicians prescribe topical antiseptics, antibiotics, and steroids for symptomatic relief. These nails heal after the drug is withdrawn, and onychomadesis (discussed in #1 above) often follows. Decreased attachment between nail keratinocytes creates scales below the proximal nail plate and a subsequent foreign body inflammation reaction.15,16 One or more nails may be affected, usually shortly after treatment starts. Paronychia (erythematous, swollen, painful nail folds) and pyogenic granuloma (a vascular tissue overgrowth) are often drug induced but stem from the same cause.Applying opaque nail polish and avoiding sun exposure can prevent this effect. It usually regresses after discontinuation of the causative agent the agents most often associated with photoonycholysis also often cause phototoxicity. 13,14 Photoonycholysis can occur after drug treatment if the drug remains in the skin. It results from drug exposure and exposure to natural sunlight or artificial light (eg, photochemotherapy). Photoonycholysis-an allergic or toxic effect of ultraviolet radiation that separates the nail plate from the nail bed-occurs in 3 subtypes: A half-moon-shaped distal onycholysis surrounded by a pigmented zone A proximal circular notch A separation in the central nail that spares the lateral portion of the nail, often in association with hemorrhages beneath the nail Considered rare, drug-induced photoonycholysis affects several fingers but spares the thumbs, and it can be painful.Dosage reduction of the offending drug can help, and this condition usually regresses over several months after drug discontinuation. The cause may be dose related, drug-induced thrombocytopenia, vascular abnormalities, direct nail bed toxicity, or peripheral nerve damage. Onycholysis-separation of the nail plate from its bed-creates a space that usually appears white.Affected patients have a greater risk of ingrown toenails and multiple periungual pyogenic granulomas (discussed below). Nail thinning and fragility may present as lamellar onychoschizia, in which the nail’s upper layers detach, or as elkonyxis, in which the nail loses substance and becomes soft or pitted.A series of thin bands (called Mees’ lines) reveals arsenic poisoning. When drug related, it usually occurs in all nails simultaneously as 1- to 2-mm horizontal bands. 1,6 In most cases, it’s the result of a minor injury. True leukonychia is the most common color abnormality of the nail, and it can present as spots, lines, or incomplete to total nail whitening. Leukonychia, also called milk spots, occurs when drugs affect keratinization.1,3,4 Onychomadesis-nail shedding or splitting-is an extreme degree of Beau’s lines. Human fingernails typically grow at about 0.1 mm/day (toenails grow at half that rate) as nails grow, Beau’s lines move upward and are eventually snipped off. A common side effect of chemotherapy and radiation, multiple Beau’s lines will develop with repeated chemotherapy cycles between treatment cycles, the nails return to normal. 3 Usually, Beau’s lines appear on all 20 nails within weeks of starting treatment. The depth of the depression reflects the amount of damage, and the depression length increases as drug exposure increases. Beau’s lines-grooved, side-to-side (horizontal) depressions in the nail surface-most often occur if a drug decreases keratinocyte cell division in the proximal nail fold. The Online Table 1-25 describes drugs associated with these alterations. 1 Let’s look at 10 types of drug-induced nail changes. Topical exposure to drugs can cause dyschromias and irritant or allergic contact dermatitis. Certain medications change digital perfusion, leading to necrosis or blood vessel damage. Drug-induced changes may accumulate in, and discolor, the nail or surrounding skin. Most drug-induced nail changes occur when a drug affects the nail epithelia, but drugs can also affect the nail matrix, the nail bed, or the periungual tissue. Drug-induced nail changes can perplex even expert dermatologists, however. The nail has several parts (Figure 1,2), and a working familiarity with nail “vocabulary” can help pharmacists identify specific nail changes.
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