What is the onset of action of diclofenac (NSAID) 75mg for acute renal colic?

Onset of Action of Diclofenac 75mg for Acute Renal Colic

Intramuscular diclofenac 75mg provides rapid pain relief for acute renal colic within 30 minutes of administration. 1, 2

Mechanism and Efficacy

Diclofenac is a first-line NSAID recommended for renal colic due to its:

• Rapid onset of action (within 30 minutes) when administered intramuscularly 1, 2
• Superior efficacy compared to many other analgesics 2
• High success rate of approximately 83-92% in treating renal colic pain 3, 4

Clinical Evidence for Onset of Action

Multiple studies confirm the rapid onset of diclofenac for renal colic:

• BMJ guidelines recommend diclofenac 75mg intramuscularly to provide pain relief within 30 minutes (Grade A recommendation) 1
• Studies show significant pain reduction at 30 minutes post-administration:
  • 75% of patients showed marked improvement within 30 minutes 4
  • Mean pain scores decreased by approximately 49% at 30 minutes 5
  • Pain relief continues to improve, reaching approximately 60% reduction by 60 minutes 5

Administration Considerations

• Intramuscular injection is preferred over oral or rectal administration for acute renal colic due to more reliable absorption and faster onset 1
• Complete pain control should be maintained for at least six hours 1
• If pain is not adequately controlled within 60 minutes, hospital admission should be arranged immediately 1

Monitoring and Follow-up

• Follow-up assessment should be performed 1 hour after initial administration 1
• If pain persists (VAS > 3) after 40-60 minutes, rescue analgesia may be required 3
• Patients should be monitored for potential side effects, though these are typically mild to moderate and occur in only 3-5% of patients 4

Contraindications and Alternatives

• Diclofenac is contraindicated in patients with:

  • Severe renal impairment
  • Heart failure
  • History of peptic ulcer disease
  • Cardiovascular disease 2

• For patients with contraindications to NSAIDs, opioids combined with an antiemetic (e.g., morphine sulfate with cyclizine) are recommended as second-line treatment 2

Patient Instructions

• Maintain high fluid intake
• Attempt to strain urine to catch any passed calculi
• Contact healthcare provider if pain worsens or new symptoms develop 1, 2

In summary, diclofenac 75mg administered intramuscularly provides rapid and effective pain relief for renal colic, with onset beginning within 30 minutes of administration and continuing to improve over the first hour.