What injection can be given to a patient with renal colic who is allergic to diclofenac (Non-Steroidal Anti-Inflammatory Drug, NSAID) for pain management?

Recommended Injectable Analgesic for Renal Colic in Patients Allergic to Diclofenac

For a patient with renal colic who is allergic to diclofenac, administer an opioid analgesic combined with an antiemetic, specifically morphine sulfate with cyclizine, given intramuscularly. 1

Primary Alternative: Opioid Plus Antiemetic

• When NSAIDs are contraindicated (including allergy), the consensus recommendation is to use an opiate combined with an antiemetic 1
• The specifically recommended combination is morphine sulfate plus cyclizine given by intramuscular injection 1
• The intramuscular route is preferred in the acute setting because oral and rectal routes are unreliable, and intravenous access may be impractical in primary care 1
• For intravenous administration if IV access is available, the usual starting dose of morphine is 0.1 to 0.2 mg/kg every 4 hours 2

Special Considerations for Renal Impairment

• If the patient has renal impairment, fentanyl is the preferred opioid because it does not accumulate active metabolites in renal failure 3, 4, 5
• Avoid morphine, codeine, or tramadol as first-line agents in patients with renal failure due to accumulation of active metabolites 3, 5
• Recent evidence from 2025 showed tramadol 50 mg IV was significantly less effective than diclofenac, with slower time to pain relief 6

Other NSAID Alternatives (If Only Diclofenac Allergy, Not All NSAIDs)

If the allergy is specific to diclofenac and not a class-wide NSAID allergy:

• Ketorolac via IV route is an effective alternative NSAID 7
• Ibuprofen via IV route showed superior efficacy in network meta-analysis 7
• Ketoprofen 100 mg IM demonstrated equivalent efficacy to diclofenac 75 mg IM with 92% success rate 8

Critical Monitoring Requirements

• Pain must be reassessed at 60 minutes after initial analgesia 1, 3
• If pain is not controlled within 60 minutes, immediate hospital admission is required 1, 3, 4
• Follow-up should occur via telephone one hour after initial assessment 1, 3
• Complete or acceptable pain control should be maintained for at least six hours 1, 5

Red Flags Requiring Immediate Hospital Admission

Before administering any analgesia, exclude:

• Patients over 60 years old: consider leaking abdominal aortic aneurysm 1, 3
• Women with delayed menses: consider ectopic pregnancy 1, 3
• Signs of shock or fever: immediate admission required 1, 3
• Sepsis and/or anuria in obstructed kidney: requires urgent decompression via percutaneous nephrostomy or ureteral stenting 3, 4, 5

Common Pitfalls to Avoid

• Do not delay analgesia while waiting for diagnostic tests 3
• Do not discharge patients before ensuring adequate pain control for at least six hours 3, 5
• Do not use standard opioid dosing in renal failure; start with lower doses and titrate carefully 5
• Be aware that opioids cause more nonspecific adverse events and vomiting compared to NSAIDs 7
• Morphine may cause respiratory depression, especially with rapid IV administration 2

Rescue Analgesia

• If initial opioid analgesia is inadequate after 40-60 minutes, consider adding 1 gram of paracetamol as rescue medication 8
• However, failure of analgesia after 1 hour mandates immediate hospital admission without further attempts at outpatient management 1