I'm a male with hypertension controlled with losartan (angiotensin II receptor antagonist) and hydrochlorothiazide (diuretic), and mild osteoarthritis (degenerative joint disease) in both knees, who recently developed a skin infection on my left wrist, treated with Bactrim (trimethoprim/sulfamethoxazole) for 7 days, and now I'm experiencing sudden onset of severe joint pain with stinging sensation and slight morning swelling, what could be causing this?

Sudden Severe Polyarticular Joint Pain Following Bactrim Treatment

You are most likely experiencing a drug-induced reactive arthropathy from Bactrim (trimethoprim-sulfamethoxazole), which can cause sudden-onset polyarthritis that mimics inflammatory arthritis and typically occurs days after completing the antibiotic course.

Immediate Clinical Assessment

The sudden onset of severe polyarticular joint pain 2 days after completing Bactrim, without fever, affecting predominantly your wrists, shoulders, and arms with stinging sensations and morning swelling, strongly suggests a drug-induced reactive arthropathy rather than infection-related complications. The timing—occurring after the infection resolved—is critical here 1.

Key features supporting this diagnosis:

• Sudden midday onset (not gradual worsening) 1
• No fever throughout (infection or Adult-Onset Still's Disease would typically cause high-spiking fevers >39°C) 2, 1
• Polyarticular distribution affecting multiple joints symmetrically 2
• Timing: 2 days post-antibiotic completion (classic for drug-induced arthropathy)
• Stinging sensation: suggests inflammatory process at joint surfaces 2

What You Need to Do Now

1. Laboratory Testing (Urgent)

You need blood work to differentiate between drug-induced arthropathy and other inflammatory conditions:

• Complete blood count with differential: Check for leukocytosis >15×10⁹/L which would suggest ongoing infection or systemic inflammatory disease 1
• Inflammatory markers (ESR and CRP): These will be elevated in true inflammatory arthritis but may be only mildly elevated or normal in drug-induced arthropathy 1, 3
• Rheumatoid factor (RF) and anti-CCP antibodies: To exclude rheumatoid arthritis, though your sudden onset makes this unlikely 3

2. Immediate Symptom Management

Stop any NSAIDs you might be taking. NSAIDs (ibuprofen, naproxen, etc.) can significantly worsen blood pressure control in patients on losartan and hydrochlorothiazide, potentially raising your BP by 5-10 mmHg 2, 4. This is especially problematic because you have hypertension and are on an ACE inhibitor-like medication (losartan) 2.

For pain relief, use:

• Acetaminophen (paracetamol) up to 3000-4000 mg daily in divided doses as your primary analgesic 2
• Ice application to the most painful joints (wrists, shoulders) for 15-20 minutes several times daily 2
• Continue your regular sit-stand exercises and walking as tolerated, as movement helps maintain joint function 2

3. When to Seek Urgent Care

Go to urgent care or emergency department if you develop:

• Fever (temperature >38°C/100.4°F) 1
• Single joint becomes disproportionately swollen compared to others (suggests possible septic arthritis) 3
• Severe uncontrolled pain despite acetaminophen 2
• New rash (salmon-pink, evanescent rash would suggest Adult-Onset Still's Disease) 2, 1

Expected Clinical Course

If this is drug-induced arthropathy from Bactrim (most likely scenario):

• Symptoms typically peak within 3-7 days after antibiotic completion
• Gradual improvement should begin within 1-2 weeks
• Complete resolution usually occurs within 4-6 weeks without specific treatment beyond symptom management

If symptoms persist beyond 4 weeks or worsen, you need rheumatology referral for consideration of:

• Inflammatory arthritis (though sudden onset makes this less likely) 3
• Post-infectious reactive arthritis 2
• Adult-Onset Still's Disease (though absence of fever makes this unlikely) 2, 1

Critical Pitfall to Avoid

Do not assume this is just a flare of your knee osteoarthritis. The sudden onset, polyarticular distribution (especially upper extremities), and timing after antibiotic treatment distinguish this from degenerative joint disease 2. Your baseline knee arthritis is degenerative and gradual; this new presentation is inflammatory and acute.

Follow-Up Timeline

• Week 1: If no improvement with acetaminophen and symptoms remain severe, contact your provider for possible short-term corticosteroid therapy (prednisone 20 mg daily for 5-7 days) 2
• Week 2-4: Symptoms should be improving; if not, obtain rheumatology referral 3
• Monitor your blood pressure closely during this period, as pain and inflammation can transiently elevate BP 2

The absence of fever throughout your entire clinical course is reassuring and makes serious systemic inflammatory disease or ongoing infection unlikely 1.