RA Drugs Flashcards
What is the aim of RA drug treatment?
- Control symptoms
- Stop progress of disease
- Restore & maintain normal function
What is the treatment for rheumatoid arthritis?
Treatment for localised problem in joints:
- Physiotherapy, occupational therapy
- DMARD’s- 1st line- methotrexate (15 mg weekly, escalated up to max 25g weekly) given w/ prednisolone (30 mg daily reducing in 5mg increments every 2 weeks until therapy is removed after 12 weeks.)
- Can also give NSAIDs w/ paracetamol
- Biologics e.g. TNF (Monoclonal antibodies)
- Local joint injection (corticosteroids) - triamicinolone, methylprednisoline
- Oral tablets - prednisolone (acute flares - daily for 2 weeks)
- IV - hydrocortisone, methylprenisolone (serious flares - daily for 3 days)
- Surgery
^Usual order- learn this order!
What are NSAIDs? Use of NSAIDs in treating RA? Examples of NSAIDs you could prescribe for RA? Dosage?
What are they?
- Anti-inflammatory
- Acts to inhibit COX —> thus inhibiting prostaglandin production= increases pain threshold
- Improve joint pain & stiffness
In RA:
- Improve joint pain and stiffness
- Effective anti-inflammatory
- Have no effect on disease activity or progression
E.g.
- Naproxen
- Aspirin
- Ibuprofen
- Celecoxib
Dosage:
- High dose needed for a few weeks
- Ibuprofen 400-800mg tds
- Naproxen 750mg stat then 250mg tds for 7 days
What is the mechanism of NSAID action?
Increases pain threshold by reversibly- inhibiting COX-1 & COX-2
COX-1= produces prostaglandin to maintain secretion of gastric mucus, platelet-initiated blood clotting & maintaining renal blood flow
COX-2= only active during inflammatory response- produces PG that mediates pain & inflammation. Responsible for anti-inflammatory action of NSAID.
During trauma, immune cells convert phospholipid cell membrane into arachidonic acid (AA)
- AA is converted to prostaglandin
- Prostaglandin is responsible for pain & inflammation
NSAIDs:
- reversibly Inhibit COX enzymes > AA not converted to prostaglandin > pain relief & anti-inflammation
i.e NSAID Prevent cycloxegenase (COX) from making prostaglandins
What are the side effects of NSAIDs & why? What could you co-prescribe to reduce side effects of NSAID?
Side effects:
1. Peptic ulcer, bleeding & perforation
- COX-1enzyme is responsible for producing prostaglandins that maintain gastric mucosal integrity & platelet initiated blood clotting
- This is why inhibition of COX-1 can lead to serious GIT side effects.
2.Increased risk of ischaemic heart disease
Co-prescribe:
- Proton Pump Inhibitors
- e.g. Lansoprazole
Contraindications of NSAIDs- who can’t have them?
- Allergy to NSAIDs or salicyate
- GI bleeding or ulcer (past or present)
- History of recurrent GI haemorrage or ulcer
- Severe heart faliure
- Severe liver impairment
- Severe renal impairment
Why do you not give aspirin to children?
Increases ammonium production in liver
leads to brain & liver damage= Reyes disease
What are DMARDS? Examples? Safety?
What are they?
- Disease Modifying Anti-Rheumatic Drugs
- Suppress inflammation & prevent permanent damage
- Used alongside corticosteroids as bridging therapy’ (short-term)
- Main therapy for RA
Examples:
- Methotrexate
- sulfasalazine
- Leflunomide,
- hydroxychloroquine,
- gold (not used)
Safety:
- Sulfasalazine - GI upset, raised liver enzymes, bone marrow suppression
- Hydroxychloroquine - retinal damage
- Leflunomide - hypertension, GI upset, bone marrow suppresion
- Gold - rash, proteinuria, bone marrow suppresion
What is Methotrexate? Safety- what is it given with? Indications of use?
What is it?
- Antimetabolite - slows growth of cells
- Folic acid antagonist- acts on folate pathway
- Best established DMARD in RhA
Safety:
- Given once a week!
- Folic acid given on another day to reduce toxicity (Methotrexate on Monday, Folic acid on friday)
- Regular monitoring required - every 2 weeks (FBC and LFT’s every 1-2 weeks until therapy is stabilised, thereafter patients should be monitored every 3-4 months)
Indications of use:
- Rheumatoid arthritis
- Psoriatic arthritis
- Reactive arthritis - only for rare occasions w/ recurrent disease or severe Kertaoderma Blennorrhagia.
- Chemotherapy
Mechanism of action of Methotrexate?
1st line drug for RA
Folic acid/ folate= important for DNA replication & repair
MOA- FOLATE PATHWAY:
- Inhibits dihydratefolate reductase (enzyme)!
- enzymes is responsible for converting to active tetrahydrofolate
- Tetrahydrofolate is needed for synthesis of nucleoside thymidine & is part of synthesis of purine & pyrimidine
- therefore, methotrexate inhibits synthesis of DNA & RNA
Why is methotrexate not given w/ trimethoprim?
Trimethoprim also acts on folate pathway
if taken together= increases risk of bone marrow suppression
- fewer blood cells in bone marrow-less oxygen= anaemia
Also reduces cells that provide immunity (leukocytes, erythrocyte)= increased risk of infection
Side effects of methotrexate?
Folic Acid deficiency!
- blood tests- all results will appear low (e.g. wcc)- pancytopenia
- therefore regular blood tests required
Avoid for following:
Pregnancy
- Shouldn’t use methotrexate- it can damage the unborn child.
Bone marrow failure
- Anaemia - fatigue!
- Thrombocytopenia - low platelet count. Presents with bruising of skin.
- Leukopenia = infections. Patients told to seek medical attention if developed severe sore throat.
- Severe bone marrow failure is rare but can be fatal.
GI side effects
- Nausea & vomitting- main side effects! (GI upset)
- Oral ulceration
- Co-prescribing folic acid or other anti-sickness meds may help w/ nausea.
- Giving methotrexate subcutaneously may help too.
Liver damage
- Hepatic cirrhosis - scarring (fibrosis) of the liver leading to long-term liver damage.
- Hepatitis- associated w/ hyper sensitivity reaction.
- Minimise alcohol!!
- Blood test monthly
Pulmonary complications
- Pneumonitis
- Pulmonary fibrosis- Presents as shortness of breath & dry cough
- Methotrexate stopped
needed- as this is more common in adults w/ pre-existing lung disease - screen for TB.
Infections
- Shingles
- Herpes
- Particularly in diabetic patients & people in steroids.
Nodulosis
- Found in pressure points or in lung
- Exacerbated by methotrexate
Drug interactions of methotrexate? What monitoring does methotrexate need?
Drug interactions
- Trimethoprim- used to treat UTIs- also acts on folate pathway !
- Septrin - antibiotic
- Both can lead to bone marrow failure after one dose.
Monitoring:
1. Monthly blood test - looks at LFT & U&E to see if liver & kidney are happy. Look at WWC & platelets to see how bone marrow is doing.
2. Baseline chest x-ray to check for lung problems and TB
Routes & frequency of administration of methotrexate?
Given WEEKLY - Methotrexate on a Monday (7.5-20 mg)
Given w/ Folic acid - given on a Friday (5 mg)
- Also advised to eat a diet high in folate e.g. beans, peanuts, fresh fruit, whole grains, green veg.
- Folic acid reduces GI side effects e.g. nausea & vomitting
- as methotrexate inhibits folate absorption- folic acid is taken- folic acid= needed in DNA synthesis
Routes of administration:
- Orally - 2.5mg or 10 mg tablets - dose is increased by increasing number of tablets.
- Subcutaneous injection - can increase efficacy by increasing bioavailability
Who should avoid Sulphasalazine?
- Anyone w/ Sulphonamide allergy
- Anyone w/ Aspirin allergy may also react.
