Peak Effect Time of Ketorolac
The peak analgesic effect of ketorolac occurs within 2 to 3 hours after administration, regardless of route (oral, intramuscular, or intravenous). 1
Pharmacokinetic Profile by Route of Administration
Oral Administration
- Peak plasma concentrations are achieved at approximately 60 minutes after oral dosing 2
- Peak analgesic effect occurs at 2 to 3 hours, which is later than the peak plasma concentration 1
- Oral bioavailability is 80-100%, making it essentially equivalent to parenteral routes in terms of total drug exposure 1, 3
Intramuscular Administration
- Peak plasma concentrations occur at 45-50 minutes after IM injection 4, 3
- Peak analgesic effect occurs at approximately 1 to 2 hours post-injection 4, 5
- The FDA label confirms the peak analgesic effect occurs within 2 to 3 hours across all dosing ranges 1
Intravenous Administration
- Peak plasma effect occurs at approximately 15 minutes due to the short lag time between injection and effect 2
- However, the peak analgesic effect still occurs at 2 to 3 hours, similar to other routes 1
- This represents the fastest onset for plasma concentrations but not necessarily for maximal pain relief 2
Clinical Implications for Timing
For procedural pain management, ketorolac should be administered 1 to 2 hours before the anticipated painful event to achieve optimal analgesia:
- Oral ketorolac 20 mg given 40 to 60 minutes before IUD placement reduced pain during and 10 minutes after the procedure 2
- Intramuscular ketorolac 30 mg given 30 minutes prior to IUD placement reduced pain at 5 and 15 minutes after placement 2
- The American College of Obstetricians and Gynecologists recommends ketorolac (20 mg oral or 30 mg IM) given 1 to 2 hours before procedures 2
Important Caveats
Duration of effect varies more than peak effect across the dosage range—larger doses provide longer-lasting analgesia rather than greater peak effect 1. The peak analgesic effect is not statistically significantly different across recommended dosage ranges, but the duration of analgesia is dose-dependent 1.
The S-enantiomer (the active form) is cleared approximately twice as fast as the R-enantiomer, with a half-life of 2.5 hours versus 5 hours, though the overall racemate half-life is 4-6 hours 1, 3.