Defined as a drug reaction that affects the structure or function of the skin, its appendages, or mucous membranes.
Common adverse skin reactions to systemic drugs include: maculopapular skin reactions; urticaria and angioedema; and the spectrum of skin lesions including fixed drug eruptions, erythema multiforme, DRESS (drug reaction with eosinophilia and systemic symptoms; also called drug hypersensitivity syndrome), Stevens-Johnson syndrome, and toxic epidermal necrolysis. Together these account for the majority of all drug-induced skin manifestations.
Any drug can cause a predictable or unpredictable reaction; those commonly implicated include beta-lactam antibiotics, muscle relaxants used in anesthesia, sulfonamides and structurally related drugs, contrast media, and gelatins.
A history of previous reactions to drugs should always be taken before prescribing.
Skin tests (prick tests, intradermal tests, patch tests) can occasionally be useful in diagnosing allergic reactions retrospectively, especially contact dermatitis.
After anaphylactic reactions, serum tryptase activity can help in diagnosis.
Cutaneous drug reactions are common.[1]Aronson JK. Adverse drug reactions: history, terminology, classification, causality, frequency, preventability. In: Talbot J, Aronson JK, eds. Stephens’ detection and evaluation of adverse drug reactions: principles and practice. 6th ed. Oxford: Wiley-Blackwell; 2011. They are adverse drug reactions (ADRs) producing a wide range of skin manifestations. An ADR may be defined as an undesirable clinical manifestation resulting from administration of a particular drug. Another definition is that of an appreciably harmful or unpleasant reaction resulting from an intervention related to using a medicinal product.[2]Health Canada. Adverse reaction information. October 2012 [internet publication].
http://www.hc-sc.gc.ca/dhp-mps/medeff/advers-react-neg/index-eng.php
An ADR may be either immunologic (i.e., drug allergy) or non-immunologic (i.e., drug intolerance). Drug allergies are estimated to account for <10% of all adverse drug reactions, with drug intolerance accounting for the other 90%.[3]Warrington R, Silviu-Dan F. Drug allergy. Allergy Asthma Clin Immunol. 2011 Nov 10;7(suppl 1):S10.
http://www.aacijournal.com/content/7/S1/S10
http://www.ncbi.nlm.nih.gov/pubmed/22165859?tool=bestpractice.com
[4]Gruchalla RS. Drug allergy. J Allergy Clin Immunol. 2003 Feb;111(suppl 2):S548-59.
http://www.ncbi.nlm.nih.gov/pubmed/12592301?tool=bestpractice.com
Adverse reactions usually predict hazard from receiving the drug in the future and warrant prevention, specific treatment, alteration of the dose regimen, or withdrawal of the product. They range from common irritant eruptions to rare, life-threatening drug-induced diseases.
A serious adverse reaction is any untoward medical occurrence that at any dose: results in death; is life threatening; requires or prolongs hospital admission; requires medical or surgical intervention to preclude permanent impairment of a body function or permanent damage to a body structure; is a congenital anomaly; or is any medical event that would be regarded as serious if it had not responded to immediate treatment.
The most common skin drug eruptions typically present as pruritus, maculopapular eruptions, urticaria, angioedema, phototoxic and photoallergic reactions, fixed drug reactions, vesiculobullous reactions, and exfoliative lesions. These manifestations clinically resemble an allergic response and are considered drug hypersensitivity reactions (DHRs).[5]Nebeker JR, Barach P, Samore MH. Clarifying adverse drug events: a clinician's guide to terminology, documentation, and reporting. Ann Intern Med. 2004 May 18;140(10):795-801.
http://www.ncbi.nlm.nih.gov/pubmed/15148066?tool=bestpractice.com
Drug reactions can be solely limited to the skin, or they may be part of a systemic reaction. Examples of systemic reactions include: toxic epidermal necrolysis (TEN); DRESS (drug reaction with eosinophilia and systemic symptoms; also called drug hypersensitivity syndrome), which consists of fever, a skin eruption, and multiorgan involvement; and acute generalized exanthematous pustulosis (characterized by fever and an acute eruption of nonfollicular pustules overlying erythrodermic skin) - although severe, this reaction is generally not life-threatening and recovery is rapid.
