Drug-induced skin reactions - Pharmaceutical Press

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146 Drug-induced skin reactions is completely normal. LDE can rarely affect the buccal mucosa; a characteristic white lace pattern may be present. 62 Idiopathic lichen planus has a predilection for the flexor aspects of the forearms and legs, whereas a lichenoid drug eruption typically has a more symmetric involvement of the trunk and extremities. 2,6 LDE tend to be extensive and may be linked with, or develop into, an exfoliative dermatitis. LDE can also result from contact dermatitis in photographic workers who handle certain p-phenylenediamines. 63 The clinical course of LDE has been investigated in many studies. The mechanism is thought to have an immunological basis. The time to onset of the reaction ranges from weeks to months after initiation of therapy. In most patients the symptoms cleared spontaneously within weeks to months of drug withdrawal. Postinflammatory hyperpigmentation can be significant and prolonged. In prolonged or severe cases, topical or systemic corticosteroids may be used. 63 Pigmentary disorders Many skin diseases are followed by changes in skin colour. In particular, after lichenoid eruptions and fixed drug eruptions there may be residual pigmentation. Drug-induced alteration in skin colour may result from increased (or more rarely decreased) melanin synthesis, increased lipofuscin synthesis, or cutaneous deposition of drug-related material (Table 5.13). Sometimes the exact nature of the pigment is unknown. The pigmentation may be widespread or localized, and pigment deposits occasionally occur in internal organs. A brown patchy pigmentation on light-exposed areas may be a result of prolonged administration of phenytoin. It occurs in about 10% of patients, and women are more likely to be affected. The pigmentation is similar to chloasma, affecting mainly the face, neck and arms. Pigmentary changes develop in about 25% of patients receiving antimalarials for more than 3 or 4 months. The shins and pretibial area are Table 5.13 Some drugs that may cause pigmentation Amiodarone (slate grey) Chloroquine (blue-grey or brown) Chlorpromazine (blue-grey) Cytotoxic agents Gold (blue-grey) Hydroxychloroquine Imatinib Mepacrine (yellow) Minocycline Oral contraceptives (brown) Phenytoin (brown) Adverse Drug Reactions, 2nd edition (ISBN: 0 85369 601 2) © Pharmaceutical Press 2006
Alopecia 147 most commonly affected. Irregular patches from grey to blue-black in colour are seen. Patients who develop this pigmentation should undergo an eye examination, as corneal depositions and retinal damage frequently coexist. Antimalarials should preferably be discontinued in affected patients, as the retinal damage is irreversible. Hyperpigmentation has been described after long-term use of minocycline and imipramine, 64 and more recently with the use of imatinib. 65–67 Alopecia Many drugs have been reported to cause hair loss (Table 5.14). The human scalp has about 100 000 hairs, 100 of which are shed daily. Human hair follicles undergo three cyclical stages: the actively growing phase of anagen, which lasts about 3 years and features 80–90% of the scalp’s follicles; the brief involutionary phase of catagen; and the resting phase of telogen, which lasts about 3 months. The telogen phase culminates in the shedding of the hair shaft and at the same time new growth in the hair follicle begins. 68–70 Hair follicles produce two types of hair according to the area of the body. Vellus hair is soft and colourless, covering the body surface apart from palms and soles. Terminal hair is the large, coarse, pigmented hair that occurs on the scalp, eyebrows, axillae etc. Drugs that induce hair loss may be classified according to the phase of the hair follicle cycle that is affected. In anagen effluvium, drugs induce an abrupt cessation of active anagen growth and the hairs are shed within days or weeks, with tapered and broken roots. Anagen hair loss is an expected pharmacological effect of cytotoxic chemotherapy and is often dose related. The hair loss is almost always reversible, but a delay of several weeks is common before regrowth begins. Alopecia is associated with alkylating agents such as cyclophosphamide, cytotoxic antibiotics such as Table 5.14 Some drugs that may cause alopecia Amfetamines Anticoagulants (warfarin, heparin, heparinoids) Antidepressants Antithyroid drugs Beta-blockers Carbamazepine Cimetidine Cytotoxic agents Hypolipidaemics Interferons Leflunomide Lithium Oral contraceptives Phenytoin Retinoids Tamoxifen Valproate Adverse Drug Reactions, 2nd edition (ISBN: 0 85369 601 2) © Pharmaceutical Press 2006
Page 1 and 2: 5 Drug-induced skin reactions Anne
Page 3 and 4: Diagnosis 127 features allowing dir
Page 5 and 6: Management points 129 severe reacti
Page 7 and 8: Fixed drug eruption 131 Table 5.3 S
Page 9 and 10: Urticaria and angio-oedema 133 with
Page 11 and 12: Psoriasis and psoriasiform eruption
Page 13 and 14: Vasculitis 137 Table 5.6 Drugs that
Page 15 and 16: Erythema multiforme, SJS and TEN 13
Page 17 and 18: Erythema multiforme, SJS and TEN 14
Page 19 and 20: Photosensitivity 143 have oral invo
Page 21: Lichenoid drug eruptions 145 sites,
Page 25 and 26: Nail disorders 149 Table 5.15 Some
Page 27 and 28: Case studies 151 CASE STUDY 5.1 (co
Page 29 and 30: References 153 References 1. Breath
Page 31 and 32: References 155 45. Smith AG. Import

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