Duration of Ketorolac Analgesia
Ketorolac provides peak analgesic effects approximately 1-2 hours after intramuscular administration, with pain relief lasting 4-6 hours, which corresponds to its recommended dosing interval of every 6 hours. 1, 2
Onset and Peak Effect
- Intramuscular ketorolac reaches maximum plasma concentrations in 45-50 minutes, with peak analgesic effects occurring at approximately 1-2 hours after injection 1, 2
- The onset of analgesic action is relatively prolonged (30-60 minutes), which limits its utility when rapid pain relief is necessary in acute settings 3
- Intravenous administration provides faster onset compared to IM, though the exact timing is less well-studied 3
Duration of Action
- The elimination half-life is approximately 4-6 hours, which directly correlates with the duration of analgesic effect 1
- Dosing intervals of every 6 hours are recommended based on this pharmacokinetic profile 4, 2
- The half-life increases in elderly patients and those with renal impairment, potentially extending the duration of action but also increasing risk of adverse effects 1
Practical Dosing Schedule
- Standard adult dosing: 15-30 mg IV every 6 hours (maximum 120 mg/24 hours for patients <65 years; 60 mg/24 hours for patients ≥65 years or <50 kg) 4
- Initial loading dose: 30-60 mg IM followed by 15-30 mg every 6 hours, with maximum first-day dose of 150 mg and 120 mg on subsequent days 2
- Lower doses (15 mg) provide equivalent analgesia to higher doses (30 mg) in elderly patients, with similar duration of effect 5
Critical Duration Limitation
- Maximum total duration of ketorolac use is 5 days due to increasing frequency and severity of adverse reactions with prolonged use 6
- This 5-day limit applies to the combined duration of IV/IM and oral formulations 6
- Patients should be switched to alternative analgesics as soon as possible 6
Common Pitfall
The prolonged onset (30-60 minutes) and significant non-responder rate (>25% in most studies) means ketorolac should not be relied upon as sole therapy for severe acute pain requiring immediate relief 3. It is most effective when used as part of multimodal analgesia or as an opioid-sparing agent 7, 8.