MSK Flashcards
Indicators of RA
Persistent inflammation affecting joints that are:
- Peripheral
- Polyarthritic
- Symmetrical
Etiology of RA
- Exact cause unknown
- genetic factors + environmental factors + chance
- 50% genetic
- 50% environmental + chance
Etiology of RA cont.
Genetic factors:
Genetic factors:
- MHC class II alleles HLA-DR4/DR1 serotypes
- Newly discovered PTPN22, PADI4, STAT4
Etiology of RA cont.
Environmental factors:
Chance:
Environmental factors:
- Cigarette smoking
- Infectious agents
- Occupational exposures (Silica dust, mineral ols)
Proposed mechanism of cause of RA
- Exposure of genetically susceptible host to unknown antigen triggering immune response
Proposed mechanism of cause of RA
- L1, pg 13
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RA pathogenesis
Normal joint:
Rheumatoid joint:
- L1, pg 14
Normal joint:
- Thin synovial membrane
- Provides lubrication
- Lack immune cells
Rheumatoid joint:
- Synovial membrane inflammation
- Antigen presenting cells, activated T & B cells
- Pannus formation
RA Pathogeneses cont’d
Step 1:
Step 2:
Step 3:
- L1, pg 16
Step 1:
- Exposure of genetically susceptible host to unknown antigen
Step 2:
- Antigen presenting cells activate T-cells (MHC II - CD4+ T), activation of B-cells
Step 3:
- Local release of proinflammatory cytokines by mo, T-cells
= Joint inflammation
RA pathogenesis cont’d
Step 4:
Step 5:
L1, pg 18
Step 4:
- Proinflammatory cytokines cause mo and fibroblasts to release matrix metalloproteinases (MMPs) degrade cartilage
Step 5: Proinflammatory cytokines cause fibroblasts to release RANKL. RANKL activates osteoclasts. Degrade bone
= Joint destruction
RA pathogenesis cont’d
Step 6:
L1, pg 20
Step 6:
- Pannus: hypertrophied synovial tissue with inflammatory cells, cytokines, and fibroblasts growing over articular cartilage and causing erosion
Signs and symptoms of RA
- RA is a systemic disease with articular and extr-articular manifestations
Non-specific symptoms:
Non-specific symptoms:
- Fatigue
- Anorexia (loss of appetite)
- Weakness
- Low grade fever
- Vague musculoskeletal symptoms (muscle pain, joint soreness)
RA signs and symptoms
Articular:
L1, pg 22
Articular:
- Symmetric polyarthritis
- Joint pain, swelling, warmth
- Morning stiffness of joints, and after rest
- Reduced range of motion, grip strength
RA signs and symptoms
Extra-articular:
L1, pg 23
Extra-articular:
- Cutaneous
- Rheumatoid nodules
- Vasculitis
- Palmar erythema
RA Classification Criteria - Serology
Rheumatoid factor (RF):
Rheumatoid factor (RF):
- RF is an IgM auto-antibody reactive with the FC portion of the patients own IgG
- The presence of RF is not specific for RA so CAN NOT be used for diagnosis or screening of RA
RA Classification Criteria - Serology
Anti-citrullinated protein antibodies (ACPA):
Anti-citrullinated protein antibodies (ACPA):
- Serum autoantibodies
- More specific for RA than Rheumatoid factor
- Detectable in early disease
RA Classification Criteria - Acute phase reactants
Erythrocyte sedimentation rate (ESR):
C-reactive protein (CRP):
Erythrocyte sedimentation rate (ESR):
- Increased in nearly all patients with RA
- Very non-specific
C-reactive protein (CRP):
- Usually increased during acute inflammation
- Also non-specific
Other RA test
- L1, pg 30
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RA goals of treatment
- There is no cure for RA
Main goals:
- Achieve disease remission
- Control disease activity (inflammation and joint destruction)
- Maintain functional ability and quality of life
DMARDs, biologics
OA epidemiology
- In patients > 55 y.o
- Hip OA is more common in males
OA at specific joints
OA of the knee:
OA of the hip:
OA of the hands:
OA of the neck/back:
OA of the foot:
OA of the knee:
- More common in females
OA of the hip:
- Occurs in males and females
OA of the hands:
- Mainly affects woman
OA of the neck/back:
- Called sponylosis
- Often asymptomatic with no problems
OA of the foot:
- Joint at base of big toe
- Interphalangeal joints
The important articular changes in OA
- Early stage
- Progression of OA
- Late stage
Early stage:
- The cartilage is thicker than normal
Progression of OA:
- joint surface is breached and vertical clefts develop (fibrillation)
- Cartilage is metabolically active
- Chondrocytes replicate and form clusters
Late stage:
- Cartilage becomes hypocellular
Pathogenesis of OA
The extracellular matrix of normal cartilage contains:
- Proteoglycans (PGs): responsible for compressive stiffness of tissue and ability to withstand load
- Collagen: provides tensile strength and resistance to shear force
- Matrix metalloproteinases (MMPs): degrade all extracellular matrix components
Pathogenesis of OA
- Primary changes occur in the cartilage
- Matrix metalloproteinases (MMPs) have an important role in the loss of cartilage matrix in OA
- Synthesis and secretion of MMPs might be stimulated by IL-1 or other factors (ie mechanical stimuli)
Symptoms of OA
- Pain (worse with activity, improved with rest)
- Stiffness after inactivity or in the morning
- Swelling, usually mild
- Reduced range of motion
- Giving way or sensation of instability
- Muscle spasm
- Sleep disturbance
- Fatigue
Signs of OA
- Gait abnormalities
- Osteophytes (bony enlargements)
- Crepitus
- Tenderness on palpation
- Deformity
- Muscle weakness
Diagnosis
L2, pg 19 & 20
- Radiographic findings in OA
Lab tests for OA
- No specific lab test available for diagnosis of OA
- Lab findings may help to identify the underlying cause of secondary OA
- ESR, CBC, urine analysis are usually normal
- Synovial fluid analysis is important in excluding other conditions (ie gout, septic arthritis, or RA
Treatment goals for OA
- reduce pain
- Improve function/minimise disability
- Improve quality of life
- Arrest (or reverse) joint destruction
Differences b/w OA and RA
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Describe the general structure of a classical NSAIDs
L3, pg 6
- Classical NSAIDs are generally made up structurally of an ACIDIC moiety (carboxylate, enol) attached to a PLANAR, AROMATIC group
- Some contain a polar linking group to an additional lipophilic group
Mechanism of action of NSAIDs
L3, pg 8 & 9
Majority of NSAIDs act as reversible inhibitors of the enzyme CYCLOOXYGENASE (COX)
- COX also known as prostaglandin synthase
- Aspirin irriversibly acylates the COX enzyme
COX catalyses the conversion of Arachidonic acid (AA) to prostaglandin H2
- Prostaglandins are mediators of inflammation
NSAIDs are acidic … except?
Paracetamol
- It is Analgesic and antipyretic but NO anti-inflammatory activity
- Paracetamol and ibuprofen can be dosed together
- Different MoA
- Not a true NSAID
MoA of paracetamol
- pretty sure dont need to know as not in the assessable tasks
- L3, pg 12 & 13 & 14
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Describe the basis of paracetamol toxicity
Metabolism:
L3, pg 17
- Normal levels of glutathione (GSH). Therapeutic doses of paracetamol
- Non-toxic conjugates. Renal excretion. Normal.
- Protein adducts -> Hepatic necrosis & renal failure
- N-acetylcysteine. Treatment for overdose (and inc. production of GSH)
Relate structure and metabolism of NSAIDs to pharmacokinetic properties
Oxicams:
L3, pg 27
Tenoxicam (funded) and Meloxicam
: Enols - pKa 6.3
- Non-classical
- Enolate stabilised by intramolecular H-bond with amide
- Ionised at physiological pH (acidic)
- Higher COX-2 selectivity
Oxicams metabolism
- Meloxicam - Slow oxidation
- hence dosed once daily
- Long half-life (20-50 hrs) due partly to lack of carboxylic acid
Understand the basis of COX-1 vs COX-2 selectivity
L3, pg 30 & 31
- Isoleucine in COX 1 replaced with smaller Valine in COX 2
- Smaller size (V) allows access to a side pocket of the main substrate channel in COX2 sterically blocked in COX1
Describe the origins of endogenous steroids
Cholesterol
- Important component of all cell membranes
- Precursor for bile acids
- Main function of bile acid - to facilitate the formation of micelles, where they emulsify dietary lipids and fat-soluble vitamins promoting absorption
- Precursor for androgens, estrogens, progesterone, adrenocorticoids
Cyclooxygenase isoforms
COX-1:
COX-2:
COX-1:
- Constitutively expressed
- Small amounts of prostanoids (basal production)
- “homeostatic” or housekeeping functions
- Renal, gastric blood flow, gastric cytoprotection, platelet aggregation
COX-2:
- Low basal expression
- Rapidly upregulated by cytokines
- Pathological”
- Large amounts of prostanoids (pain, inflammation, fever)
- Understand the role of cyclooxygenase in actions of NSAIDs
- Relate actions and (unwanted) effects of NSAIDs to mechanism of action
- Start to predict the most appropriate NSAID for different patients (children/elderly/CV or renal disease) based on above knowlege
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Epidemiology of OA
- Most common form of arthritis
- Onset in 40’s and 50’s
- Over half of people in 70s have OA
- Women»_space; Men
OA Treatment goals
- Educate patients about disease & treatment
- Alleviate symptoms
- Prevent or slow progression
- Maintain function & maximize QoL
OA Treatment
- Nonpharmacologic treatment
- Exercise (weight loss)
- Thigh weakness inc. knee arthritis
- Paracetamol
- 1st choice
- Can combine with low dose NSAIDs
- Recommendations:
- ROM, strength, aerobic, wt bearing, isometric, aquatics
Topical agents for OA
Topical NSAIDs & capsaicin
- Suboptimal relief with acetaminophen, or who cannot tolerate or are reluctant to use systemic agents
- Intitial NSAID therapy should be topical rather than oral in persons >75 years old
Topical therapies may also be tried as adjunct to systemic agents where pain relief is not adequate
- Both agents should be applied 3-4 times daily
- Maximal effect can take up to 2 weeks for topical NSAIDs and 4 weeks for topical capsaicin
NSAIDs for OA
- Due to their risk of serious adverse effects NSAIDs are considered 2nd line therapy after failure of acetaminophen
- NSAIDs are often preferred by OA patients due to better pain relief
NSAIDs monitoring OA
Prior to starting long-term NSAID therapy
- assess patients for their risk of cardiovascular, GI and renal complications
If patient has no risk factors
- ibuprofen 200-400 mg Q8H or naproxen sodium 220 mg Q12H
- Over a 1- to 2- week trial, the dose can be titrated until adequate pain relief is achieved or the maximum dose is reached
- Avoid long-term therapy, but if continued therapy is needed, use the lowest effective dose
NSAIDs toxicities
L5, pg 16, 17, 18
- Gastrointestinal
- Cardiovascular & renal
- Thrombosis
Duloxetine
- Duloxetine is an antidepressant approved for use in osteoarthritis of the knee
- Duloxetine may be used as monotherapy or in combination with acetaminophen of NSAIDs for OA of the hip and knee if treatment with these agents has not provided adequate pain relief
- Common side effects include nausea, fatigue and constipation
Intra-articular steroids
Limited to acute knee pain with local signs of inflammation and joint effusion
- Aspiration of fluid followed by intra-articular injection of corticosteroid has a small and temporary effect (4-6 weeks) on pain and function
- Repeated injection may damage cartilage
- The same site should not be injected more than 3-4 times per year
Not studied in hand and hip OA
Hyaluronic acid for OA
- Hyaluronan is a linear polysaccharide found in synovial fluid
- 3 weekly injections have a comparable effect to 5 weekly injections
- Reserved for patients who have failed other therapies as costs are high
Summary of OA treatment
- Non-drug therapy is place to start
- weight loss, exercise
- Paracetamol 1g po qid
- Progress if no response
- NSAIDs are effective but potentially toxic
- Monitor efficacy and safety
Methotrexate
- MoA:
MoA:
- Inhibition of aminoimidazolecarboxamide (AICAR) trabsformylase. Inhhibits degradation of adenosine. anti-inflammatory effects
- Inhibition of proinflammatory cytokine production
- Inhibition of dihydrofolate reductase. anti-proliferative effects of immune cells
- Inhibition of thymidylate synthetase. with secondary effects on polymorphonuclear chemotaxis
- Induction of apoptosis?
Methotrexate
- Side effects:
pic on L6, pg 15
- Stomatitis
GI:
- Diarrhoea
- Hepatotoxixity
Teratogenic: contraindicted in pregnancy
Methotrexate
- Route of administration:
- Onset of action:
Route of administration:
- PO, SC
Onset of action:
- 2-3 weeks
Hydroxychloroquine
- Proposed MOA:
- Onset of action:
- Route:
Proposed MOA:
- Suppression of T-cells, inhibition of leukocyte chemotaxis, inhibition of DNA and RNA synthesis
Onset of action:
- 6 weeks
Route:
- PO
Hydroxychloroquine
- Side effects
CNS:
- Dizziness, headache, insomnia, dreams
Ocular toxicities:
- Blurred vision
- Dec. accommodation
GI:
- N, V, D (dec. by taking with food)
- May be used in pregnancy
Sulfasalazine
- Proposed MOA:
- Onset of action:
- Route:
Proposed MOA:
- Sulfapyridine component. antirheumatic properties
- Dec. IgA and IgM RF production
- Inhibition of in vitro B cell proliferation
Onset of action:
- 2 months
Route:
- PO
Sulfasalazine
- Side effects:
GI
- N/V/D, anorexia
Derm:
- hypersensitivity reactions
Skin & urin may turn yellow-orange
Safe for pregnancy
Leflunomide
- MOA:
- Onset of action:
- Route:
MOA:
- Inhibits dihydroorotate dehydrogenase
- Inhibits protein synthesis
- Competitive inhibitor of pyrimidine synthesis. Dec. lymphocyte proliferation & modulation of inflammation
Onset of action:
- 4-6 weeks
Route:
- PO
Leflunomide
- Side effects
- Hepatotoxicity
- Hypertension
- HEME: bone marrow toxicity
- GI: diarrhoea
- DERM: Alopecia
- Teratogenicity
Etanercept
- MOA:
- Onset of action:
MOA:
- Binds TNF-a in the circulation and in the joint, preventing interaction with cell surface TNF,a receptors. Dec. TNF activity
Onset of action:
- 1-4 weeks
Etanercept
- Side effects:
CNS
- Demyelinating syndromes
ID:
- Inc URTI
Heme:
- Blood dyscrasis
Infliximab
- MOA:
- Onset of action:
MOA:
- Binds TNF-a in the circulation and in the joint, preventing interaction with cell surface TNF-a receptors. Dec. TNF activity
Onset of action:
- Days to weeks
infliximab
- Side effects
Infusion related:
- “cytokine release syndrome” A clinical syndrome of fever, chills and headache
- Manage by slowing the infusion rate
Sepsis and disseminated TB and other opportunistic infections
Adalimumab & Golimumab
- MOA:
- Onset of action:
MOA:
- Binds TNF-a in the circulation and in the joint, preventing interaction with cell surface TNF-a receptors. Dec. TNF activity
Onset of action:
- Weeks to months
Adalimumab & Golimumab
- Side effects:
CNS:
- Demyelinating syndromes
ID:
- Inc URTI, bronchitis, UTI
- Inc. risk for serious and opportunistic infection (ie TB)
Tocilizumab (Actemra)
- MOA:
- Onset of action:
- Side effects:
MOA:
- Binds membrane bound and soluble IL-6 receptor, inhibit binding of IL-6 to receptor and downstream signalling effects including T-cell activation, OC activation
Onset of action:
- 3 months
Side effects:
- Elevated liver enzymes
- Elevated lipids & triglycerides
- Neutropenia
- GI perforation
Rituximab
MOA:
Rituximab depletes B-cells through three different mechanisms:
- Complement-mediated B-cell lysis
- Cell-mediated cytotoxicity via macrophages and natural killer (NK) cells
- Apoptosis by activation of different caspases
Rituximab (Rituxan)
- MOA:
- Onset of action:
- Side effects:
MOA:
- Binds CD20 expressed on surface of B cells and depletes them via multi mechanisms, depletion of B cells suppresses the RA disease process
Onset of action:
- 2 months
Side effects:
- Infusion reactions
The goals of therapy of RA:
- Achieve remission
- Control disease activity
- Maintain functional ability
- Quality of life
Why treat RA early?
- Treat RA early to prevent irreversible joint damage
Treat-to-target strategy for RA
- L8, pg 9
- Treat early and aggressively until target is reached
- Target = remission (or low disease activity)
Commonly used DMARDs
L8, pg 13
Methotrexate
- Why is this a ‘go-to’
- This is our ANCHOR drug unless containdicated
- PO or SC (SC preferred as less toxicity
- Folic/folinic acid supplementation reduces ADRs
Biologics: common adverse effects
- upper respiratory infections (colds, sinusitis, bronchitis, etc)
- Injection site reactions (SC agents)
- Infusion reactions (IV agents) - itching, hives, headache, palpitations
- Skin rash
- Dizziness
- Nausea, diarrhoe
- Headache