Related Experiment Video
Updated: Aug 14, 2026
10:22
Basophil Activation Test for Investigation of IgE-Mediated Mechanisms in Drug Hypersensitivity
Published on: September 16, 2011
Phenytoin hypersensitivity syndrome with positive patch test. A possible cross-reactivity with amitriptyline
P A Galindo Bonilla1, G Romero Aguilera, F Feo Brito
1Division of Allergy, Hospital of Ciudad Real, Spain.
Summary
A patient developed a phenytoin drug eruption with liver dysfunction. Patch testing confirmed phenytoin allergy, suggesting possible cross-reactivity with amitriptyline.
Area of Science:
- Dermatology
- Clinical Pharmacology
Background:
- Drug eruptions are hypersensitivity reactions to medications.
- Phenytoin and amitriptyline are commonly prescribed for various conditions.
Observation:
- A 34-year-old woman presented with fever, rash, and eosinophilia after 2 weeks of phenytoin and amitriptyline.
- Biochemical tests revealed abnormal liver function (elevated SGOT, SGPT, LDH, GGT, ALP).
- Skin biopsy indicated a phenytoin drug eruption, erythema multiforme-like type.
Findings:
- Patch testing was positive for phenytoin, showing an eczematous pattern.
- Patch testing with amitriptyline was negative, but an oral challenge elicited a rash.
- Phenytoin challenge was contraindicated due to abnormal liver function.
Implications:
- Patch testing can aid in diagnosing phenytoin allergy.
- Cross-reactivity between phenytoin and amitriptyline is a possibility.
- This case highlights the importance of considering drug-induced hypersensitivity reactions.
Related Concept Videos
01:27Allergic Drug Reactions
Allergic reactions related to drugs are hypersensitivity responses driven by the immune system and bear no connection to the drug's therapeutic action. While drugs in isolation do not trigger an immune response, they can interact with endogenous proteins to form antigens. These antigens stimulate lymphocytes to produce antibodies. IgE-type antibodies attach themselves to mast cells. Upon subsequent exposure to the same stimulus, the antigen-antibody interaction is initiated, unleashing numerous...
01:20Desensitization and Tachyphylaxis
Tachyphylaxis is described as a rapid decrease in response to a drug after repeated or continuous administration of the same drug dose. It is a phenomenon where the body becomes less responsive to a particular substance or intervention over time, requiring higher doses or stronger interventions to achieve the same effect. It results from adaptive changes in the body's receptors, signaling pathways, or physiological processes that occur in response to prolonged exposure to a stimulus.
Several...
Several...
01:24Drug Toxicity: Dose-Dependent Reactions
Drug toxicities can be stratified into pharmacological, pathological, or genotoxic based on their mechanisms. The incidence and severity of these toxicities generally increase with the drug's concentration in the body and exposure time.Pharmacological toxicity is evident when the therapeutic effects of drugs overshoot into adverse reactions in a predictable, dose-dependent manner. Central nervous system (CNS) depression from barbiturates is a classic example, with effects escalating from...
01:30Drug Toxicity: Allergic Reactions
Drug-related allergies are immune-mediated responses triggered by the administration of pharmacological agents. These hypersensitivity reactions are classified based on the immune mechanisms involved. The four primary types—Type I, II, III, and IV—are mediated by different immunological pathways and exhibit distinct clinical manifestations.Type I Hypersensitivity/ IgE-Mediated Reactions: Immunoglobulin E (IgE) immediately mediates Type I hypersensitivity reactions. Upon initial exposure to a...
01:29Hypersensitivity Reactions: Delayed Hypersensitivity Reactions
Delayed-Type Hypersensitivity (DTH), or Type IV hypersensitivity, is a cell-mediated immune response. It occurs when T cells, rather than antibodies, mediate a reaction to specific antigens. It is characterized by a delayed onset (1-2 days) and involves the recruitment of macrophages to the inflammation site.The initiation of a DTH response begins with the sensitization of T cells. During this phase, which lasts at least 1-2 weeks, antigen-specific T cells are activated, clonally expanded, and...
01:16Drug toxicity: Idiosyncratic Reactions
Idiosyncratic drug reactions represent abnormal chemical responses that vary significantly among individuals, ranging from extreme sensitivity to low doses to insensitivity to high doses. These reactions often occur due to the drug's covalent binding with serum proteins, forming a foreign hapten that triggers an immunotoxicological response. The variability in drug reactions has a strong pharmacogenetic foundation, with genetic differences crucial in how individuals metabolize drugs. For...