immune-mediated toxicities Flashcards
What is drug hypersensitivity reactions (DHR)?
- Activation of immune or inflammatory cells that leads to ADR
- Types of ADR
- Type A: Pharmacologically mediated and predictable based on drug
- Type B (10-15%): DHR
what are the Types of drug hypersensitivity reactions?
- Immune (Allergy)
- Non-immune (Pseudoallergy)
what is immune drug hypersensitivity reaction?
allergy
- Immunologically mediated hypersensitivity reaction to a drug/ antigenic substance in a sensitised person
- Sensitised person when exposed to drug again —> Immune system recognise as threat —> Triggers immune response —> Host tissue damage due to release of inflammatory mediators —> Localised (organ-specific) or generalised systemic reaction
what are the Types of allergic reactions?
note: Atopy: Genetic tendency to develop allergic diseases such as allergic rhinitis, asthma and atopic dermatitis (eczema)
Type I: Immediate hypersensitivity or Atopy
Type II: Antibody-mediated disease
Type III: Immune-complex mediated disease
Type IV: T cell-mediated disease
whats the pathologic immune response for Type I: Immediate hypersensitivity or Atopy?
Th2 cells, lgE antibody, mast cells, eosinophils
whats the pathologic immune response for Type II: Antibody-mediated disease?
lgM, lgG antibodies against cell surface or extracellular matrix antigens
whats the pathologic immune response for Type III: Immune-complex mediated disease?
Immune complexes of circulating antigens, lgM, lgG antibodies deposited in vascular basement membrane
whats the pathologic immune response for Type IV: T cell-mediated disease?
CD4+ T cells (cytokine mediated inflammation), CD8+ CTLs
tell me more about how Genetic disposition can increases susceptibility to drug hypersensitivity syndromes
Variations in genetically determined human leukocyte antigen (HLA) alleles
Genetic factors can influence metabolic deactivation of drugs via phase 1 and 2 metabolism —> Extent of active metabolite remaining
what are the Types of drugs commonly associated with allergic reactions?
- Beta lactam
- Sulfonamide
- Anticonvulsants
- Some chemo agents
- Radiocontrast media
- Chlorhexidine
- ACE/ ARB
- Biologics (proteins)
- NSAIDs
- Insulin
what are the Effectors categories of allergic reactions?
- Innate and adaptive immune systems
- chemical mediators
what are the Effectors (Innate and adaptive immune systems) of allergic reactions?
- Cellular elements: Macrophages, T & B lymphocytes, platelets, mast cells
- Mast cell when exposed again will flare up
- Immunoglobulins: lgE
- Complements: Activates mast cells and inflammatory mediators
- Cytokines
what are the Effectors (chemical mediators) of allergic reactions?
- Histamine: Stored and released from basophils and mast cells
- Platelet-activating factor (PAF) and Thromboxane: Triggers platelets aggregation and clots so hypersensitivity reaction to anticoagulant heparin
- Prostaglandins (PG), Leukotrienes: Dilators or constrictors for bronchoregulation
summarise the Effectors of allergic reactions
- Mast cells release and break down agents which are involved in Type I reaction, Vasodilation —> swelling and hypotension, Increased vessel permeability, Broncho smooth muscle contraction —> Loss of breathing
- Basophils, neutrophils, eosinophils recruited later for delayed sensitivity
what is a life threatening Clinical manifestation of allergic reactions?
- Anaphylaxis
- Acute, life-threatening reaction involving multiple organ systems
- Risk of fatal anaphylaxis greatest within first few hours
- Most common by penicillins, NSAIDs, insulins
what is the signs and symptoms of anaphylaxis?
- Skin: Hives, swelling
- Airway*: Tightness and swelling
- CNS: Anxiety, headache, tunnel vision
- CVS*: Chest pain, low bp, rapid HR
- GIT: N/v, abdominal cramping, diarrhoea
- Serum sickness/ Drug fever
- Alot of antigens in body —> binds with other antibodies to form immune complex which circulates throughout body to trigger inflammation and systemic reactions
- Commonly by antibiotics
- Drug induced autoimmunity
- Common conditions
- Systemic lupus erythematosus (SLE)
- Hemolytic anemia (RBC burst): Commonly by Methyldopa
- Hepatitis: Commonly by phenytoin
- Vasculitis
- Inflammation and necrosis of blood vessel walls
- Limited to skin or involve multiple organs
- Commonly by Allopurinol, thiazide
- Respiratory
- Common conditions
- Asthma: Commonly by NSAIDs
- Fibrotic pulmonary reactions —> Acute and chronic Fibrosis in lungs: Commonly by bleomycin (chemotherapy agent), nitrofurantoin (antibiotic for UTI)
- Common conditions
- Hematologic (blood type reaction)
- High levels of eosinophilia
- Common conditions
- Hemolytic anemia
- Thrombocytopenia
- Agranulocytosis (neutrophil counts drop to dangerous levels)
what is serious cutaneous adverse reaction (SCAR)?
one of the signs of anaphylaxis
- Drug rash with eosinophilia and systemic symptoms (DRESS)
- 3 Criteria: Triad of rash, lots of eosinophils, internal organ involvement (commonly hepatitis, interstitial nephritis,interstitial pneumonia,orcarditis (inflammation of heart muscle) etc)
- High mortality rate 10%
- Commonly by Allopurinol, anticonvulsant
what is Mucocutaneous disorders?
one of the signs of anaphylaxis
- Dermatologic emergencies as can progress to cause mucous membrane erosion and epidermal detachment, Commonly by antibiotics (esp sulfonamides)
- Stevens-Johnson syndrome (SJS): Disorder of skin and mucous membrane
- High mortality rate 1-5%
- Toxic epidermal necrolysis (TEN)
- Very high mortality rate 10-70%
- Stevens-Johnson syndrome (SJS): Disorder of skin and mucous membrane
what is the Treatment for anaphylaxis?
- Restore respiratory and CV function
- First line: Epinephrine (adrenaline)
- Acts on alpha and beta receptors to counteract bronchoconstriction and vasodilation (increase bp)
- Epi-pens for those with severe allergies
- Second line (at hospital)
- IV fluids to restore volume/ BP
- Intubation to save airway
- Norepinephrine (noradrenaline) if shock
- Steroids to suppress reaction
- Diphenhydramine (H1) and Ranitidine (H2): Blocks histamine receptors to stop or slow down reaction
- Glucagon (if patient on beta blockers): Help heart beat regularly
what is the treatment for SCAR (serious cutaneous adverse reaction)?
- No known cure
- Just stop drug
- Manage symptoms via supportive care
- Wound care, nutritional support, fluids, temperature regulation, pain management and prevention of infections
- Steroids (controversial)
- IV immunoglobulin and cyclosporine
what is Non-immune (Pseudoallergy)?
- Mimic true allergies but do not involve immune system, not caused by allergen-specific immune responses
- 77% of hypersensitivity reactions
- Release mediators like histamine, prostaglandins, kinins from mast cell, basophil (NOT lgE)
what are some common drugs that cause pseudoallergy?
- Vancomycin
- Infusion reaction aka Red man syndrome if infused too quickly —> So slow down infusion
- Direct release of histamine from mast cells and other mediators
- Itching, flushing, hives
- Onset around neck and face first then progresses to chest and other parts
- ACE/ Sacibitril
- Angioedema
- Inhibition of breakdown of bradykinin —> vasodilation —> increases vascular permeability —> edema, inflammation
- NSAIDs
- NSAIDs induced asthma
- Alter metabolism of prostaglandins esp in lining of lungs —> anaphylaxis
What is autoimmune disease?
- Body attacked by own immune system —> auto antibodies formed
- Risk factors
- Genetic background
- If have variations in genes —> more susceptible to create autoantibodies when stimulated by environmental factors
- Environmental stimuli like smoking and infection
- Genetic background
- At least 80 known autoimmune diseases
what is the Treatment of autoimmune disease?
- Target, block and hence dont activate B cells to produce autoantibodies and T cells to exert cytotoxic effects
- Target cytokines
- Target Kinases
why is autoimmune disease Difficult to treat ?
- Many targets to treat, so many ways for autoimmune disease to continue
- No or lose response to treatment, cannot tolerate treatment, ADR to treatment
- Rare so minimal trials to get drugs approved so available drugs are poorly indicated (most off-label) and costly (not covered under insurance)
- Great variability of treatment among centres
- Having autoimmune disease seen as weakness, so less likely to seek help
what are the Types of autoimmune disease?
note: Organ or not organ specific, depending on type of autoantibody —> to a specific cell or receptor or floating around body
- Systemic lupus erythematosus (SLE) - Non organ specific
- Psoriasis
- Grave disease
- Type 1 DM
- Rheumatoid Arthritis
- Multiple sclerosis
- Sjogren’s syndrome
- Scleroerma
- Systemic vasculitis
how does systemic lupus erythematosus (SLE) happen?
- Apoptosis of cells releases cell contents including nucleic acids which float around body —> DNA and RNA act as autoantigens —> SLE kicks in: Autoantibodies formed anywhere in body which binds with nucleic acids —> immune complex formed and interact with APCs with MHC —> MHC presents immune complexes to T cells and stimulate B cells to produce more autoantibodies —> activate cytokines and symptoms
- Autoantibodies and antiphospholipid antibodies produced
where can systemic lupus erythematosus take place?
- Multi-system as immune complex can be anywhere in body
- Complexes collect in smaller vessels —> blockage in brain, kidney, joints and hands, CVS —> diseases
what are the risk factors of systemic lupus erythematosus?
- More prevalent in females, non-white, African descent than asian
- Strong genetic disposition
- UV light
- Epstein-Barr virus
- Pollution
- Drugs (refer to drug-induced lupus)
what is the clinical physical presentation for systemic lupus erythematosus?
note: Disease fluctuates with periods of remission, flares and progression in 70% of patients
- Skin diseases appear in 50-70% of patients
- Rheumatoid arthritis: Affects joints
- Neurological disease
- Serostitis: Inflammation of serous membrane (pleura, pericardium, peritoneum), affects heart, lungs
- Fever, aching alot
- Lupus nephritis —> Kidney failure
- Only cure is transplant
- Neuropsychaitric lupus
- Stroke
- CVS
- Note that statin has DDI with some lupus medications
what is the clinical presentation lab signs for systemic lupus erythematosus?
- Full blood count decreased due to:
- Hemolytic anemia —> RBC decrease
- Leukopenia —> WBC or lymphocytes decrease as autoantibodies destroy WBCs
- Thrombocytopenia —> Platelets decrease as autoantibodies destroy platelets
- Immunologic
- High Autoantibodies
- Antinuclear antibody (ANA)
- Antidouble-stranded DNA (dsDNA)
- Anti-Smith antibody (anti-Sm)
- Antinuclear ribonucleoprotein (anti-RNP)
- Low complement (C3, C4, CH50) when immune complexes activate the complement system, leading to complement protein cleavage and consumption
- High antiphospholid antibodies —> Antiphospholid syndrome in 40% of SLE patients
- Lupus anticoagulant
- Anticardiolipin
- Anti-beta2 glycoprotein I
- High Autoantibodies
what is the clinical implications of having high antiphopholipid antibodies in someone with systemic lupus erythematosus?
- Risk of thrombosis (blood clot)
- High risk of preggo morbidity: Might be reason for high occurrence of miscarriage
what can be done for someone with high antiphopholipid antibodie?
preggos
- Nothing can be done :(
- Put on parental anti-coagulant
non preggos
- Primary thromboprophylaxis: Asprin to get rid of clots
- Secondary thromboprophylaxis: Warfarin (NOT USED FOR PREGGOS)
- Hydroxychloroquine has protective effect in suppressing clotting factors
what is the treatment goals for systemic lupus erythematosus?
- Goal: Remission where disease is inactive so minimal symptoms
- Prevent flares and other organ involvement, slow disease, reduce use of steroids, improve QOL, minimise ADR
- Need to treat comorbidities too
- Lifestyle and support groups for mental health