Pharmacology: Adverse Drug Reactions

Nonimmune Drug Hypersensitivity Reactions

• Vancomycin infusion can cause pruritus and an erythematous rash involving the face, neck, and "red man" reaction when administered over less than 1 hour.

Life-threatening Cutaneous Drug Reactions

• Examples of life-threatening drug reactions include Stevens-Johnson syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) or Drug-induced Hypersensitivity Syndrome (DIHS).

Drug-induced Hyperpigmentation

• Can be caused by increased melanin (e.g., hydantoins) or direct deposition (e.g., silver, mercury, tetracyclines, and antimalarials).

Drug-induced Photosensitivity Reactions

• Can be phototoxic (nonimmunologic reaction) or photoallergic (immunologic reaction).
• Medications associated with phototoxicity include amiodarone, tetracyclines, sulfonamides, and coal tar.
• Common causes of photoallergic reactions include sulfonamides, sulfonylureas, thiazides, nonsteroidal anti-inflammatory drugs (NSAIDs), chloroquine, and carbamazepine.

Radiocontrast Media

• Can cause serious, immediate nonimmune hypersensitivity reactions, such as urticaria/angioedema, bronchospasm, shock, and death.
• Reactions occur in 0.7% to 3% of patients.
• Typical protocols include pre-treatment with prednisone and diphenhydramine.

Opiates

• Stimulate mast cell mediator release directly, resulting in pruritus and urticaria with occasional mild wheezing.
• Pre-treatment with an antihistamine may reduce these reactions.

Cancer Chemotherapy

• Hypersensitivity reactions have occurred with all chemotherapy agents.
• IgE-mediated type I reactions are the most common.
• Reactions are most common with taxanes, platinum compounds, asparaginases, and epipodophyllotoxins.
• To reduce the risk, patients are routinely premedicated with corticosteroids and H1- and H2-receptor antagonists.

Anticonvulsants

• Can cause a wide range of hypersensitivity reactions, ranging from mild maculopapular skin eruptions to severe life-threatening reactions.

Treatment of Drug-induced Skin Reactions

• Discontinuing the suspected drug as quickly as possible and avoiding use of potential cross-sensitizers is the most important treatment.
• Controlling symptoms (e.g., pruritus) is the next step.
• Systemic corticosteroids may be warranted in severe cases.
• Photosensitivity reactions typically resolve with drug discontinuation.