12.1 Rheumatology: Gout, Osteoarthritis & Inflammatory Arthritis

12.1 Rheumatology: Gout, Osteoarthritis & Inflammatory Arthritis

Quick Answer: APC names rheumatology as an Intern Written exam content area. High-yield material is acute gout treatment (colchicine dosing limits and interactions), urate-lowering therapy targets and traps, osteoarthritis analgesia that respects renal and gastrointestinal risk, and weekly methotrexate safety in inflammatory arthritis.

Rheumatology sits across Standards 3.1, 3.2 and 3.3. You assess the presentation, choose or check therapy, and monitor for the harms that make these medicines dangerous in ordinary community practice. Almost every rheumatology item in an intern exam is really a safety item wearing a joint-pain costume.

Gout — recognise it before you treat it

Features that suggest a gout flare:

• Rapid onset with maximal inflammation within 24 hours
• First metatarsophalangeal joint (podagra) is classic, but midfoot, ankle and knee are common
• Local erythema, heat and extreme tenderness (bedsheet intolerance)
• Hyperuricaemia supports the diagnosis but a normal urate during a flare does not exclude gout

The presence of tophi and a clear response to colchicine are more diagnostically useful than urate level alone. Red flags that mean referral, not OTC advice: fever with a hot swollen joint (septic arthritis until proven otherwise), a first presentation in an unusual joint, or a person who is systemically unwell.

Acute flare treatment options

The single most examinable colchicine number is the maximum. Old regimens that dosed colchicine hourly "until relief or diarrhoea" are obsolete and dangerous. Low-dose colchicine is as effective as high-dose with far fewer adverse effects.

Colchicine interactions — a genuine harm pathway

Colchicine is a substrate of CYP3A4 and P-glycoprotein. Concurrent inhibitors raise colchicine exposure toward toxicity:

• Macrolides (clarithromycin especially, erythromycin)
• Non-dihydropyridine calcium channel blockers — diltiazem, verapamil
• Calcineurin inhibitors — ciclosporin
• Protease inhibitors and some antifungals
• Interaction relevance also extends to digoxin and dabigatran through P-glycoprotein

A patient on verapamil who is handed a colchicine script and a clarithromycin course for a chest infection is a classic exam stem. The answer is to contact the prescriber before supply, not to dispense and hope.

Urate-lowering therapy (ULT)

ULT is preventive treatment, not flare treatment. Core principles:

• Allopurinol is first line. Start low (commonly 50–100 mg daily, lower in renal impairment) and titrate upward against serum urate.
• Treat to a target serum urate below 0.36 mmol/L (a lower target, commonly quoted as below 0.30 mmol/L, is used where tophi are present).
• The maximum recommended allopurinol dose in Australia is 900 mg daily.
• Do not stop ULT during an acute flare. Stopping and restarting causes urate shifts that provoke more flares. Treat the flare and continue the allopurinol.
• When starting or increasing ULT, flare prophylaxis is recommended for at least six months — low-dose colchicine (commonly 500 micrograms twice daily with normal renal function, 500 micrograms daily in renal impairment) or an NSAID, with low-dose prednisolone as a second-line option.

Allopurinol safety

• Severe cutaneous adverse reactions (including DRESS and Stevens–Johnson syndrome / toxic epidermal necrolysis) are rare but potentially fatal. Any new rash on allopurinol means stop and seek medical review the same day — never "push through it".
• Risk of severe cutaneous reaction is higher in people carrying HLA-B*5801, which is more prevalent in Han Chinese, Thai and Korean populations; guidance in some settings recommends testing before initiation, particularly with coexisting chronic kidney disease.
• Allopurinol plus azathioprine or mercaptopurine causes profound, potentially fatal myelosuppression through xanthine oxidase inhibition. This is a stop-and-call-the-prescriber interaction, covered again in the gastrointestinal and high-risk medicines material.
• Febuxostat is an alternative xanthine oxidase inhibitor used when allopurinol is unsuitable; cardiovascular history is part of the risk conversation.

Medicines that move urate

If a person with gout needs antihypertensive therapy, a thiazide is a poor structural choice; losartan may be favourable. This is exactly the kind of "which comorbidity changes the drug choice" reasoning Standard 3.1 tests.

Osteoarthritis — analgesia without organ damage

Osteoarthritis is the most common arthritis you will counsel on at the counter. The pharmacist's job is graded, safe analgesia plus non-pharmacological reinforcement.

1. Non-pharmacological first and always — exercise and strengthening, weight management, heat, pacing, appropriate footwear, physiotherapy referral.
2. Topical NSAID — a sensible first pharmacological step for knee and hand osteoarthritis; systemic exposure is much lower than oral therapy.
3. Paracetamol — modest benefit; still reasonable for some people, and safer in renal impairment than an NSAID.
4. Oral NSAID — lowest effective dose, shortest duration, only after screening renal function, cardiovascular history, GI risk, heart failure and current medicines.
5. Opioids — not a routine osteoarthritis therapy; the risk profile rarely justifies chronic use.

The triple-whammy check. An older person on an ACE inhibitor or ARB plus a diuretic who adds an NSAID is at high risk of acute kidney injury, especially with dehydration. Screen for this every single time an NSAID is requested or dispensed — it is one of the most repeated safety patterns in Australian pharmacy assessment.

Inflammatory arthritis — methotrexate and friends

Rheumatoid arthritis and related inflammatory conditions bring disease-modifying antirheumatic drugs (DMARDs) into community pharmacy.

Immunosuppression counselling generalises: infection is the recurring risk. Advise prompt medical review for fever or sore throat, discuss vaccination status (live vaccines are generally avoided with significant immunosuppression — inactivated vaccines including influenza and COVID-19 are encouraged), and reinforce that the person should tell every prescriber about their DMARD.

Putting it together for the exam

A rheumatology stem will usually hide the real question inside a plausible request:

• "Can I have something stronger for my gout?" → check what else they take, whether colchicine has already been used within three days, and whether renal function permits an NSAID.
• "My rash started after the new gout tablet." → allopurinol rash is a stop-and-review event.
• "Methotrexate 10 mg, take one daily." → verify with the prescriber before supply.
• "Ibuprofen for my knee, and here's my usual perindopril and indapamide." → triple whammy; offer paracetamol or a topical NSAID and explain why.

Know the colchicine maximum, the urate target, the weekly methotrexate rule and the triple whammy cold. They convert directly into marks.