CSB601 Chap.10 Pain, NSAIDs, Osteoarthritis and Rheumatoid Arthritis
Pain, NSAIDs, Osteoarthritis and Rheumatoid Arthritis
What this chapter covers
Week 8 of the unit joins pain physiology to two very different joint diseases. You will sort pain into nociceptive, neuropathic and mixed types, then connect each type to paracetamol, NSAIDs or neuropathic adjuvants.
A pathway figure shows how cyclo-oxygenase inhibition produces both relief and gastrointestinal, renal and cardiovascular harm, including the triple whammy with diuretics and ACE inhibitors.
How the arthritis material is organised
Osteoarthritis is handled as a symptom-control problem with a stepwise plan built on exercise, weight loss and regular paracetamol.
Rheumatoid arthritis is handled as an autoimmune disease that needs early DMARD therapy, with methotrexate safety points (weekly dosing, folic acid, blood monitoring) worked through in a model case. Where lecture slides and the newer lecture page disagree, both readings are shown.
What this chapter covers
- 01
Pain Types and Mechanisms
- 02
Paracetamol Dosing and Overdose Risk
- 03
COX Inhibition and NSAID Harms
- 04
Triple Whammy Kidney Risk
- 05
Stepwise Osteoarthritis Management
- 06
Rheumatoid Arthritis DMARD Therapy
Worked example · free
Escalating pain relief for hand osteoarthritis
- 2Classify: age over 50, use-related aching, asymmetric involvement, stiffness well under 30 minutes and nodes at the distal finger joints (Heberden's nodes) all point to osteoarthritis, a mechanical disease where the goal is symptom control and function.
- 2Optimise the first step before escalating: paracetamol works best taken regularly in divided doses as background therapy, not only on bad days, and non-drug measures such as exercise, splints and mobility aids sit underneath every step.
- 2Plan the next steps: a topical NSAID can be added with paracetamol, then an oral NSAID used intermittently at the lowest effective dose. Opioids are contested: older slides place a weak opioid third while the newer lecture page advises against them, so follow current unit guidance.
Key terms
- Triple Whammy
- A combination of a diuretic, an ACE inhibitor or sartan and an NSAID that together reduce kidney perfusion and raise the risk of acute kidney injury.
- Multimodal Analgesia
- A pain plan that combines different drug classes with non-drug therapies so that efficacy improves while adverse effects fall.
- Conventional Synthetic DMARD
- A disease-modifying antirheumatic drug such as methotrexate, leflunomide, sulfasalazine or hydroxychloroquine, used first line in rheumatoid arthritis.
- Selective COX-2 Inhibitor
- An NSAID such as celecoxib or meloxicam that mainly blocks COX-2, sparing COX-1 gut protection but possibly raising cardiovascular events.
- Heberden's Nodes
- Bony swellings at the distal finger joints that signal osteoarthritis of the hand.
Pain, NSAIDs, Osteoarthritis and Rheumatoid Arthritis FAQ
Why is paracetamol still recommended if it only reduces pain a little?
Most analgesics in clinical use reduce pain intensity by roughly 30 percent, and none abolishes pain outright. Paracetamol has a strong safety record at recommended doses, is suitable in pregnancy and breastfeeding, and performs better when taken on a schedule. Its weakness is inflammation, which is why NSAIDs are reserved for pain with an inflammatory driver.
Is a COX-2 selective NSAID safe for someone with a stomach ulcer history?
Not automatically. Selective agents cause fewer gastrointestinal effects than non-selective ones, but those effects still occur, and the lecture keeps them contraindicated in peptic ulcer and reflux disease, merely preferred over older NSAIDs. They may also carry more cardiovascular events, so heart risk has to be weighed in the same decision.
Why must methotrexate for rheumatoid arthritis be taken only once a week?
Methotrexate is cytotoxic and immunosuppressive. Taken daily by mistake, it can cause serious myelosuppression and liver toxicity. Weekly scheduling, folic acid supplementation and regular blood counts, liver tests and kidney tests are the standard safety package. Teratogenic effects mean it is avoided in pregnancy and breastfeeding.
How do I tell osteoarthritis from rheumatoid arthritis in a short-answer case?
Look at stiffness duration, symmetry and systemic features. Brief morning stiffness under half an hour, pain worse with activity and one-sided joint involvement suggest osteoarthritis. Stiffness lasting beyond 30 to 60 minutes, matching joints on both sides, inflammation persisting more than six weeks and fever or fatigue suggest rheumatoid arthritis, which changes the goal to disease control.
Exam move
Start by drawing the cyclo-oxygenase pathway from memory, marking where non-selective NSAIDs and coxibs block it, then annotate each branch with the harm it explains: gut, kidney, platelets or heart. Next, build a two-column card for osteoarthritis and rheumatoid arthritis covering driver, stiffness time, symmetry, treatment goal, first-line therapy and the role of NSAIDs.
Rehearse the OA steps aloud in order, and practise saying where the slides and the newer lecture page disagree on opioids and on RA sequencing. For methotrexate, memorise one compact line: weekly dose, folic acid, blood counts plus liver and kidney tests, avoid in pregnancy.
Finally, write three short invented patients, one neuropathic, one on an anticoagulant and one with a diuretic plus ACE inhibitor, and decide in under two minutes which analgesic each should avoid and why. Timed practice like this matches the multiple-choice and short-answer mix of the final exam.
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