What is the duration of action of diclofenac (Nonsteroidal Anti-Inflammatory Drug (NSAID)) injection for pain relief?

Duration of Action of Diclofenac Injection for Pain Relief

Diclofenac injection has a duration of action of approximately 4-6 hours for pain relief, with onset of action within 30 minutes of administration. 1, 2

Pharmacokinetic Profile

• Onset of action:

  • Intravenous (IV) bolus: Within 15-30 minutes 3, 2
  • Intramuscular (IM): Within 30 minutes 4

• Peak effect:

  • Typically occurs 1.5-2 hours after administration 5

• Duration of action:

  • 4-6 hours for single dose administration 2, 6
  • Median time to need for rescue medication: 4.3-4.9 hours (compared to 2 hours for placebo) 6

Formulations and Administration

Diclofenac injection is available in different formulations:

• Traditional formulation: Contains propylene glycol and benzyl alcohol as solubilizers, requiring slow IV infusion over 30 minutes 2

• Novel HPβCD formulation (Dyloject®):

  • Solubilized with hydroxypropyl β-cyclodextrin
  • Can be administered as a small volume IV bolus
  • Provides faster onset of analgesia compared to traditional formulation 2
  • Available in doses of 18.75 mg, 37.5 mg, and 75 mg 3

Efficacy Considerations

• Both 18.75 mg and 37.5 mg doses of HPβCD diclofenac provide significant analgesic efficacy compared to placebo 3

• Efficacy is comparable to IV ketorolac 30 mg, another commonly used injectable NSAID 3, 2

• Single-dose HPβCD diclofenac 75 mg IV bolus shows superior total pain relief over 4 hours compared to traditional diclofenac formulation, indicating faster onset of analgesia 2

• Diclofenac injection significantly reduces the need for rescue opioid medications 3

Clinical Applications

Diclofenac injection is particularly useful for:

• Acute moderate-to-severe pain management following surgery 3, 2
• Renal and biliary colic, where it is comparable or superior to many narcotic and spasmolytic combinations 4
• As part of multimodal analgesia in cancer pain management 7

Practical Considerations

• Dosing frequency: Every 6 hours as needed for pain 3
• Maximum daily dose: 150 mg 7, 1
• Duration of treatment: Use the lowest effective dose for the shortest duration possible to minimize adverse effects 1

Safety Profile

• Generally well tolerated compared to other NSAIDs 4, 5
• The novel HPβCD formulation has a lower incidence of thrombophlebitis compared to traditional formulations 2
• No dosage adjustments are typically required in elderly patients or those with renal or hepatic impairment 4
• The relatively short elimination half-life (1.5 hours) limits potential for drug accumulation 4, 5

Diclofenac's relatively short duration of action (4-6 hours) should be considered when planning pain management strategies, particularly for patients requiring around-the-clock analgesia who may need repeated dosing or alternative longer-acting analgesics for continuous pain control.