3. HYPERSENSITIVITY
Hypersensitivity refers to the undesirable reactions
produced by the normal immune system , including allergies
and autoimmunity
These reactions may cause damaging , uncomfortable or
occasionally fatal
These reactions require a presensitized state of the host
4. DRUG HYPERSENSITIVITY;
It is an immunologically mediated reaction producing
symptoms unrelated to pharmacodynamic actions of the drug
generally occuring with much smaller amounts and have a
different time course of onset and duration
These reactions account for about 1/6th of all ADR’S
The most common allergic reactions occurs in skin and
observed 2-3% in hospitalized patients
5. Antibiotics and antiepileptics are the drugs most frequently
causing hypersensitivity reactions
The severity and symptoms depends up on the immune
activation and duration of treatment , sex
8. IGE MEDIATED
IgE antibodies is ready to react to small amounts of antigens
Stimulate receptors bound ige antibodies
The drug causes formation of tissue sensitive ige antibodies
that are fixed to mast cells
Subsequent exposure of drug activate leucocytes and release of
chemical mediators that cause allergy
9.
10. CYTOTOXIC ;
The mediator of these reactions are IgE /IgM membrane
attack complex
It results when drug binds to RBC and is recognised by IgE
antibodies
The Ag- Ab reactions trigger the lysis of RBC either by
activating complement system or by action of cytotoxic T cells
or by phagocytosis of macrophages leads to disintegration of
cell
11. EXAMPLES ;
Seen in high dose pencillin and cephalosporin
Quinine induced immune thrombocytopenia
Heamolytic anemia
12. IMMUNE COMPLEX ;
These reactions occurs within 1 – 2 hours of drug
administration
Soluble antigen antibody forms soluble complexes
deposited on vascular endothelium and activate complement
Characterized by allergic inflammatory reactions in tissues
13.
14. CLINICAL FEATURES ;
Vasculitis
Sulphamethoxazole , cephalexin , amoxicillin , NSAID’S
and diuretics
15. DELAYED REACTIONS ;
These reactions mediated by T cell and macrophages
Activation of T cell release of cytokines these activate
macrophages and NK cells
The term delayed because the response occurs after 48 – 72
hours after antigen response
Pnemonitis , contact dermatitis
16. PSUEDOALLERGY ;
Pathogenically poorly determined , alternation in
metabolism of histamines .
Detection of particular immune mechanism is negative
The exact mechanism is unknown by which these cause
reactions through IgE / T cells or not
These reactions mainly occurs when taken of NSAID’S
17. CLINICAL SYMPTOMS OF
DRUG HYPERSENSITIVITY;
Urticaria
Erythema
Stevens john syndrome
Epidermal necrosis
18. DIAGNOSIS ;
Patient symptomology
IgE
Skin testing
RAST testing
Antiglobulin test
ESR , CRP , ANA
Patch test lymphocyte proliferation assay
19. TREATMENT ;
Discontinuation of drug
Alternative medications
Additional therapy to manage symptoms caused by drugs
Systemic corticosteroids and antihistamines may improve
dermatological effects