For a patient with suspected renal colic presenting with loin pain, which is the preferred analgesic: intramuscular diclofenac (Voltaren), intravenous paracetamol, or intravenous/IM hyoscine butylbromide (Buscopan)?

Preferred Analgesic for Suspected Renal Colic

Intramuscular diclofenac (Voltaren) 75 mg is the preferred first-line analgesic for acute renal colic, providing rapid pain relief within 30 minutes with Grade A evidence. 1, 2, 3

Primary Recommendation: IM Diclofenac

• Diclofenac 75 mg IM is the gold standard for renal colic analgesia, with consensus recommendation from the European Association of Urology and BMJ guidelines. 1, 2

• The intramuscular route is specifically preferred because oral and rectal routes are unreliable in acute settings, and IV administration may be impractical. 1, 4

• Pain relief should be achieved within 30 minutes of administration, with adequate control maintained for at least 6 hours. 1, 4

• Recent network meta-analysis confirms diclofenac IM is superior to opioids and has more robust evidence than other NSAIDs. 5

• A 2025 randomized controlled trial demonstrated diclofenac 75 mg IM provided significantly faster pain relief (37 minutes vs 79 minutes) compared to IV tramadol, with 94% achieving pain relief within 120 minutes. 6

Why NOT Paracetamol IV

• Paracetamol is not recommended as first-line therapy for renal colic in any major guideline. 1, 2, 3

• While one article mentions IV paracetamol has comparable efficacy to morphine and diclofenac, this is not supported by guideline-level evidence and NSAIDs remain superior. 7

• NSAIDs reduce the need for additional analgesia compared to non-NSAID options and provide superior pain control. 2

Why NOT Buscopan (Hyoscine Butylbromide)

• Buscopan is an antispasmodic, not an analgesic, and has no role as primary pain management for renal colic. 1, 2

• Combining antispasmodic agents with analgesics does not improve efficacy over analgesics alone. 8

• No guideline recommends antispasmodics as first-line or standalone treatment for renal colic pain. 2, 3

Clinical Algorithm

Step 1: Assess for contraindications to NSAIDs 2, 3

• Renal impairment (low GFR)
• Cardiovascular disease
• History of GI bleeding
• Pregnancy
• Known NSAID/salicylate allergy

Step 2: If no contraindications exist:

• Administer diclofenac 75 mg IM immediately 1, 2
• Reassess pain at 60 minutes 1, 3

Step 3: If contraindications present:

• Use opioid (morphine, fentanyl) combined with antiemetic (cyclizine) 1, 2
• In renal impairment specifically, use fentanyl (no active metabolites) and avoid morphine, codeine, or tramadol 2

Step 4: If pain not controlled at 60 minutes:

• Immediate hospital admission required 1, 3
• Consider repeat IM analgesic injection or admission for pain control 1, 3

Critical Caveats and Red Flags

Immediate hospital admission required if: 3

• Fever or signs of systemic infection (suggests obstructive pyelonephritis—surgical emergency) 3
• Hemodynamic instability or shock 3
• Failure of analgesia within 60 minutes 1, 3
• Age >60 years (consider leaking AAA) 1, 3
• Women with delayed menses (consider ectopic pregnancy) 1, 3

NSAID safety considerations: 2

• Use lowest effective dose in patients with borderline renal function 2
• NSAIDs increase cardiovascular and GI risks, particularly in elderly with comorbidities 2
• Monitor renal function carefully in at-risk patients 2

Follow-Up Protocol

• Telephone follow-up 1 hour after initial assessment to verify pain control 1, 3
• Instruct patient to maintain high fluid intake and strain urine 1, 3
• Arrange fast-track renal imaging within 7 days 1, 3
• If stone >5 mm in distal ureter, consider alpha-blocker (tamsulosin) for medical expulsive therapy 2