DRUG  ERUPTIONS

Drug  eruptions are probably the most frequent manifestation of drug sensitivity. Their true incidence is difficult to determine because mild and transitory eruptions are often not recorded and because skin disorders may be falsely attributed to drugs. Certain patient groups are at increased risk of developing an adverse drug reaction. The ampicillin induced rash seen  in patients with Infectious mononucleosis is a classical example. Elderly patients and patients with AIDS appear predisposed to adverse drug reactions. Most commonly drugs causing  adverse drug reactions  are  Antimicrobial agents, Antipyretic/ Antiinflammatory analgesics, Antipschycotics & Antihypertensives agents.

1)    EXANTHEMATIC( MACULOPAPULAR REACTIONS):

Definition  and  Clinical features:

The  commonest of all cutaneous drug eruptions, occurring in 2-3% of patients, and seen with almost any drug at any time up to 3 weeks after administration.

Typically, there is fine erythematous morbilliform maculopapular eruption of the trunk and extremities that may become confluent. Exanthematic drug reactions often start in areas of trauma or pressure and can be very variable,with either predominantly small papules, or large macules , a reticular eruption , or polycyclic or sheet – like erythema. Intertriginous areas may be favoured, palmar & plantar involvement can occur and face may be spared. Purpuric lesions are common on the legs and erosive stomatitis may develop. Drug  exanthema  may be accompanied by fever,pruritus and eosinophilia. These eruptions usually  fade with desquamation, sometimes with post inflammatory hyperpigmentation.

Drug Associations:

Drugs commonly causing exanthematic reactions include—ampicillin  & penicillin, sulfonamides, phenylbutazone, phenytoin, carbamezapine,gentamicin  and gold.

2)    BULLOUS DRUG ERUPTIONS:

Definition, Clinical features and Drug Associations:

This is a heterogenous group involving many different clinical reactions & mechanisms. Pemphigus  and  pemphigoid  may be drug induced. Penicillamine  induced pemphigus is usually of the foliaceus type, while captopril  causes a pemphigus vulgaris type eruption. Cicatricial pemphigoid has been described with clonidine  and  previously with practolol. Fixed eruptions and drug induced vasculitis may have a bullous component, while toxic epidermal necrolysis has widespread blistering. A number of drugs may induce phototoxic bullae. Bullae, often at pressure points, can be present in patients comatose after overdosage with barbiturates, methadone, tricyclic antidepressants and benzodiazepines.

3)    URTICARIA:

Definition and clinical features:

Urticaria is the second most common allergic cutaneous reaction to drugs. Allergic urticaria is the cutaneous manifestation of a Type 1( IgE antibody mediated) or Type 3(immune complex mediated) hypersensitivity reaction. Some drugs,e.g. morphine & codeine, can act as direct histamine liberators. Urticaria  may accompany serum sickness reactions or systemic anaphylaxis.

Urticaria  appears as firm,erythematous,oedematous  plaques with normal  overlying epidermis and no scaling. Lesions characteristically last for less than 24 hours and are replaced by new lesions in different sites. Giant, papular, arcuate and annular lesions may be seen. Angio-oedema may occur. Pruritus is prominent and bronchospasm,hypotension and eosinophilia may occur. Urticaria usually resolves quickly when the offending drug is withdrawn but,not uncommonly,episodes of urticaria may persist for several weeks after drug discontinuation.

Drug Associations:  

Penicillin and salicylates are common provokers. Other commonly implicated agents includes blood products,vaccines,radiocontrast agents,NSAIDS,opiates,cephalosporins & ACE inhibitors.

4)    STEVENS-JOHNSON SYNDROME:

Definition and clinical features:

Stevens-Johnson syndrome is a severe variant of erythema multiforme(EM) characterized by widespread involvement of mucosal surfaces.

A prodrome of fever, malaise and prostration is followed by eruption of mucosal bullae, with or without the widespread cutaneous target lesions of EM. Mucosal  surfaces, commonly the oral mucosa, respiratory tract and conjunctiva may be extensively involved and secondary infection is common. Morbidity is significant with pain, ocular complications, respiratory compromise,dysuria and difficulty maintaining adequate oral fluid intake.

Drug Associations:

Erythema Multiforme is more commonly precipitated by various infections,but both EM and S J Syndrome can be drug induced. Commonly incriminated are sulfonamides,NSAIDS, barbiturates, phenylbutazone, phenytoin, carbamezapine, phenothiazines, chlorpropamide, thiazide diuretics and malaria prophylaxis.

5)    FIXED DRUG ERUPTION:

Definition and clinical features:

A cutaneous reaction that characteristically recurs in the same site(s) each time the drug is administered. Usually just one drug is involved but cross-sensitivity to related drugs may occur. Typical lesions are well demarcated, round or oval,erythematous,dusky plaques with subsequent post inflammatory hyperpigmentation. Bullae are quite common.Lesions arise within 8 hours of drug administration and are common on the extremities, genitalia and perianal areas, Mucous membrane may be involved.

Drug Associations:

A large number of drugs have been reported,but especially tetracyclines, sulphonamides, oxyphenbutazone and fluroquinolones are known to cause fixed drug eruption.

BY:

DR CHETAN LALSETA

                            M.D.(SKIN & V.D.)

CONSULTANT DERMATOLOGIST & COSMETOLOGIST

MIRROR LASER & COSMETIC CENTRE,

SHRADDHA HOSPITAL,

INDIRA CIRCLE CHOWK,

RAJKOT-04

CONTACT NO: 98251 99585