AIM To clarify which reactions reported by

patients are likely to be the result of true drug allergy in the context of all adverse drug reactions

To understand the immunological basis for drug allergy

To be able to make recommendations to optimise patient care based on this knowledge

A response to a medication that is noxious, unintended or undesired occurring at doses normally used for the prevention, diagnosis or treatment of disease

WHO

Most ADR’s (85-90%) are predictable, dose-dependent and related to the pharmacology of the drug Clin Pharmacol Therap 2011; 90(3): 455-60

Toxicity – e.g. digoxin Intolerance – e.g. colchicine Secondary effects – e.g. oral steroids Special situations – e.g. renal impairment in

the elderly Drug interaction – e.g. SSRI and tramadol

Unpredictable, unrelated to the known pharmacology of the drug, with no clear dose dependency (10-15%). Drug hypersensitivity reactions and Drug Hypersensitivity Syndrome constitute a major part of type B reactions

Clin Pharmacol Therap 2011; 90(3)

TYPE MEDIATOR PATHOGENESIS

CLINICAL PICTURE

CHRONOLOGY

1 IgE Degranulation of mast cells and basophils

Urticaria; anaphylaxis; allergic rhinitis; bronchospasm; angioedema

Immediate (< 1hr)

2 IgG/M FcR-dependent cell lysis

Blood cell dyscrasia

Intermediate (5-14 days)

3 IgG/M FcR-dependent immune complexes deposition

Serum sickness; vasculitis

Intermediate (7-8 days)

4 Th1 (IFNγ, TNFα), Th2 (IL4. 5, 13), Cytotoxic T cells

Monocyte/macrophage eosino neutrophil inflamm

Eczema, maculopapular, bullous exanthem

Delayed (weeks)

Refers to reactions characterised by a delayed onset constellation of symptoms including fever, rash, and multiple organ involvement

Classes of drugs most often associated with DHS include beta lactam antibiotics, sulfonamides, minocycline, terbinafine, azathioprine, allopurinol and NSAID’s

Clin Pharmacol Therap 2011; 90(3): 455-60

high fever sore throat / pharyngitis gritty eyes, photophobia mouth or genital ulcers swollen tender lymph glands, and/or head

and neck swelling or puffy eyes malaise, myalgia, arthralgia and/or arthritis headache, neck stiffness dyspnoea, cough, rhinorrhoea and/or ear

pain skin tenderness

allopurinol antiepileptics (phenytoin,

carbamazepine, phenobarbitone, lamotrigine)

nonsteroidal anti-inflammatory drugs (NSAIDs)

sulfonamide antibacterials antiretrovirals (nevirapine, abacavir) penicillins, cephalosporins

Simple exanthematic eruptions are the most common type of drug eruption. They mimic the full spectrum of infective exanthems. Typically the rash begins on the trunk and upper limbs. It is usually polymorphous with morbilliform or urticarial lesions on the limbs, confluent lesions on the upper chest, and purpuric lesions on the ankles and feet.

Onset: Typically 5 to 14 days after starting a new medication, or hours to days on rechallenge. Reactions can also occur after drug withdrawal.

Implicated drugs: Almost all medications have been associated with exanthems, but most frequent reports are with antibacterials (beta lactams, macrolides, quinolones and sulfonamides), many antiepileptics, allopurinol, antiretrovirals, nonsteroidal anti-inflammatory drugs, gold, blood products and cytotoxic drugs.

Clinical course: Exanthematic eruptions often progressively worsen for several days after the drug is stopped, before resolving over 7 to 14 days with minor desquamation.

Management: Stopping the offending drug is usually all that is required, but if necessary consider treating symptoms while the rash resolves.

Mast cells and basophils are granulocytes produced in the bone marrow. Mast cells are found throughout the body in connective tissues close to blood vessels and particularly in the respiratory, genitourinary and gastrointestinal tracts. They both release their granules as a result of the binding of allergen to IgE, which sits on their cell surface through its Fc receptor. Also as the (direct)result of some drugs (e.g. opioids, radiocontrast agents)

Asthma Rhinitis Urticaria Allergic dermatitis (e.g. atopic*) Food hypersensitivity Anaphylaxis Stinging insect allergies

* Atopy is a condition of secreting IgE in response to common environmental allergens

Allergen binds to IgE on mast cells, which degranulate and Release pre-formed inflammatory

mediators Synthesize other mediatorsPreformed inflammatory mediators:

Histamine

Tryptase

Heparin

Synthesized mediators:

PGD2

LTC4

Lehman JM & Blaiss MS. Drugs 2006:66918):2309-2319.

DRUG Urticaria Angioedema Bronchospasm Localised or whole-body immediate type

(anaphylactic) reactions

DISEASE/CONDITION Atopic dermatitis Food allergies Asthma Rhinitis

1ST dose of antigen

2nd dose of antigen

Mucous membrane

Lymph node

IgE

Sensitised mast cell

Release of mediators

Any organ may be affected, but the skin is most commonly involved

The most common reactions are maculopapular rashes, urticaria and pruritis

Penicillin induced anaphylaxis occurs in 1 in 5000 to 1 in 10,000 courses

Patients with HIV and infectious mononucleosis have higher rates of allergic reactions

For patients with a history of penicillin allergy who require a cephalosporin, treatment depends on whether the previous reaction was mediated by IgE

N Engl J Med 2006;354(6): 601-07

Urticaria, angioedema, anaphylaxis, maculopapular skin eruptions, exfoliative dermatitis, vesicular eruptions, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, serum-sickness-like reactions, vasculitis, cytopenia’s.

N Engl J Med 2006; 354(6): 601-7

Urticaria, angioedema, anaphylaxis, maculopapular skin eruptions, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, renal dysfunction, toxic nephropathy, hepatic dysfunction, aplastic anemia, hemolytic anemia.

N Engl J Med 2006; 354(6): 601-7

An antigen must be a macromolecule, either a large protein or polysaccharide, in order to activate lymphocytes to generate antibody formation.

If an antigen is too small to generate an immune response by itself, it is called a hapten.

Mucocutaneous – rhinitis, conjunctival erythema and tearing, flushing, itch, urticaria, angioedema.

Abdominal/pelvic – nausea, vomiting, abdominal pain.

Neurological – vascular (throbbing) headache, dizziness, confusion, incontinence, collapse (with or without unconsciousness (associated with hypoxia)

Respiratory/chest – upper airway angioedema dysphagia and stridor, throat and/or chest tightness, dyspnoea, cough, wheeze, cyanosis

Cardiovascular – palpitations, tachycardia,

hypotension, arrest.

COMMON Insect stings: most commonly honeybee,

Australian native ants, wasps Foods ; most commonly peanuts, tree

nuts, egg, seafood, cows milk, dairy products, seeds

Medications: most commonly antibiotics, NSAID’s

Unidentified: no cause found

MJA Practice Essentials Allergy 2007

1. Stop administration of causative agent2. Call for assistance3. Give adrenaline IM (lateral thigh) 0.01

mg/kg (maximum dose 0.5 mg)4. Lay patient flat (elevate legs if

tolerated)5. Give high flow oxygen +

airway/ventilation support if needed6. If hypotensive, IV saline bolus 20ml/kg

over 1-2 minutes under pressure.

Medications such as antihistamines and corticosteroids have no proven impact on the immediate and dangerous effects of anaphylaxis, although they may ameliorate mild allergic reactions confined to the skin.

MJA Practice Essentials Allergy 2007

NSAID ingestion (including aspirin) may provoke asthma and rhinitis

This may affect 5-10% of people with asthma It involves a non-immune hypersensitivity

mechanism of increased leukotriene production caused by inhibition of COX-1 enzyme

MJA Practice Essentials Allergy 2007

Angioedema is a well recognised adverse reaction that affects 0.1 - 0.5% of patients

It can first appear anywhere from a few hours to 8 years after an ACEI is taken

Up to 20% of cases can be life threatening

The reaction involves a non-immune hypersensitivity mechanism caused by the accumulation of plasma kinins

MJA Practice Essentials Allergy 2007

Mediated by antigen/antibody complexes• Complexes may settle in tissues and

excessively activate complement• Complement in turn activates

neutrophils and macrophages (or the complex may do this directly)

• Tissue destructive lytic enzymes or phagocytosis follows

• Complexes commonly affect blood vessels, renal glomeruli and synovial joints

Takes longer than antibody mediated reactions

Damage may be caused by cytokines released from T helper cells or by activated T cytotoxic cells