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Pamela A. Davol, 76 Mildred Avenue, Swansea, MA  02777-1620.
pdavol@labbies.com


Dermatologic (Skin) Disorders of the Dog:
A Multipart Series

Allergic Drug Reactions Affecting the Skin

Dermatologic Conditions Associated with Adverse Drug Reactions

Similar to adverse reactions to food that may lead to symptoms of dermatitis, adverse reactions to drugs, immunological or non-immunological, may cause skin reactions in the dog. When dermatologic eruptions occur following exposure to systemic drugs, including injectable or oral medications, or topical drugs, such as shampoos, dips, or ointments, a hypersensitive drug reaction should be considered as a possible cause.

Indications Consistent with a Diagnosis of Drug Reaction

History of exposure to the drug

Symptoms suggestive of a drug reaction and unexplained by any other cause

Biopsy specimen indicating histopathologic features of a drug eruption

Resolution of clinical symptoms following drug withdrawal

A negative challenge with other concurrently used drugs*

*The decision to challenge with the suspected, causative drug to confirm hypersensitivity to that specific drug must be carefully considered based upon the health risks (the possibility of fatal outcome) associated with re-introduction of that drug. Such risks may only be warranted if the dog's life is dependent upon the drug and there are no substitute drugs available).

 

Symptom

Related Drug

Treatment

Prognosis

Pruritis (itchiness)

Allergy immunotherapy vaccines; miscellaneous drugs; benzyl peroxide-, tar-, or herbal-based shampoos; flucytosine; pyrethroid dips and sprays

Drug withdrawal*; antihistamines

Favorable prognosis in most cases with symptoms responding to treatment; dogs should be monitored, however, for possible progression to more serious symptoms

Urticaria-angiodema (hives-swelling of the face and occasionally the respiratory tract)

Vaccines, blood products, bacterins, venom and other biologics; Antibiotics (penicillins, sulfonamides, tetracyclines, etc.); Parasiticides (amitraz, levamisole, ivermectin); barbituates; contrast medium (used in diagnostic imaging); flucytosine; amphotericin B; shampoo; benzyl peroxide

Drug withdrawal*, antihistamines and glucocorticoids until symptoms resolve; severe systemic reactions require epinephrine and emergency supportive therapy

Mild reactions typically resolve with treatment; evidence of systemic symptoms require monitoring for possible progression to life-threatening anaphylaxis

Maculopapular Lesions (rash-like reddening of the skin due to surface blood vessel dilation)

Antibiotics; shampoos (citrus-based, herbal based, coal tar-based, benzyl peroxide); levamisole

Drug withdrawal*; antihistamine and prednisolone (if required)

Lesions resolve within 14 days of drug withdrawal and treatment. This condition must be differentiated from more serious conditions of purpura or erythema multiforme

Erythroderma (reddening of the skin accompanied by scaling)

Shampoos (herbal-, citrus-, tar-, and benzyl peroxide-based); dips (herbal and antiparasitic-based); antibiotics

Drug withdrawal*

Condition typically resolves within 7 days of drug withdrawal, but scaling may continue for 2-3 weeks accompanied by extensive hair loss. Hair will regrow.

Vesiculobullous lesions (blister-like, ulcerative, often circular lesions)

Triamcinolone; antibiotics (penicillins, sulfonamides, tetracycline); parasiticides (levamisole, diethylcarbamazine); cimetidine; aurothioglucose; thyroxine; anticonvulsants

Drug withdrawal*; systemic forms may require high-dose glucocorticoid therapy and supportive therapy for secondary complications (liver necrosis, anemia, thrombocytopenia)

Eruptions confined to localized areas typically resolve after 2 weeks of drug withdrawal; systemic conditions may affect liver and other systems of the body and prognosis is guarded in such cases

Epidermal Necrosis (ulcerative lesions)

Antibiotics (cephalaxin, trimethoprim-sulfadiazine, penicillins, griseofulvin); 5-flucytosine; aurothioglucose; antisera; D-limonene; levamisole; herbal flea shampoos

Drug withdrawal*; fluid therapy, antibiotics, and corticosteroids; severe and extensive conditions require supportive therapy to prevent dehydration, secondary infection, sepsis, and electrolyte imbalance associated with extensive skin loss

This condition has a guarded prognosis. Dogs experiencing epidermal necrosis are usually in pain and systemically ill. Anemia and liver and kidney damage may also occur. Supportive care is usually essential until the condition resolves. Severe forms of this condition are similar in severity to what is seen in third degree burn victims, with extensive skin damage resulting in skin sloughing, depression, shock, coma and often death.

Injection-site reactions

(lesions associated with hair-loss, crusting, ulceration, or necrosis; and in cats: granuloma and fibrosarcoma)

Glucocorticoids and progestogens; vaccines (rabies, distemper, hepatitis, and dermatophyte); antibiotics; anthelmintics (praiquantel)

Most lesions are self-limiting and resolve without therapeutic intervention; serious reactions may require surgery to provide cure

Lesions may take months to resolve spontaneously and often leave scar tissue; surgery may be utilized for cosmetic purposes or as a curative approach for severe lesions

Purpura

(immune-complex induced hemorrhage into the dermal tissues)

Azathioprine; chlorambucil; cyclophosphamide; antibiotics (penicillin, sulfonomides, tetracycline); non-steroidal anti-inflammatories and aspirin; levamisole; aurothioglucose; estrogens; vitamin K analogues (overdose or poisoning); vaccines

Drug withdrawal*, control of hemorrhage; supportive therapy with high-dose glucocorticoids or transfusion may be required in severe cases

Withdrawal of the drug accompanied by glucocorticoid therapy until the drug is cleared from the system is usually sufficient for stabilizing the patient

* In cases where reaction is associated with a topical agent, the dog should be washed with copious amounts of tepid water to completely remove the agent.
Table adapted and modified from: Mason KV. Therapy for Drug Eruptions. pp.557.

Additional Considerations

In many instances of mild drug reactions, removal or withdrawal of the agent is all that is required for recovery. In moderate to severe cases, therapeutic intervention is typically required to reduce symptoms and prevent secondary complications. Drug reactions resulting in skin damage often require topical and/or systemic treatment to control opportunistic bacterial infection and induce skin regeneration. In cases in which the primary drug reaction was precipitated by an antibiotic, special consideration must be given to the use of other antibiotics since some antibiotics used as follow-up may cross-react with the offending antibiotic and induce another reaction.

Clipping hair and removing dead skin and crusted material assists by allowing more successful topical treatment of the affected area. In some instances of severe skin damage, moist, anti-septic bandages may need to be applied. Additionally, dogs with systemic symptoms or extensively compromised skin surface areas typically require administration of fluids, plasma, or whole blood transfusions dependent upon the severity of the reaction or dermal compromise.

 

References:

Mason KV. Therapy for Drug Eruptions. In Kirk's Current Veterinary Therapy XIII, Bonagura, J.D. (ed.), W.B. Saunders Co., Philadelphia, 1999. pp.556.

Scott DW, Miller WH Jr., Griffin CE. Drug Eruptions. In: Muller and Kirk's Small Animal Dermatology, WB Saunders, Philadelphia, 1995. pp.590.


Copyright 2001. Pamela A. Davol. All rights reserved. Copyright & disclaimer.

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