ASA and NSAIDs

In Ontario paramedic practice, NSAID administration—such as ketorolac or ibuprofen—is contraindicated if the patient has taken any NSAID within the previous 6 hours. This includes ASA when given at therapeutic doses. The Analgesia Medical Directives list “NSAID/Ibuprofen use within 6 hours” as an absolute contraindication for both ketorolac and ibuprofen.

Low‑dose ASA (81 mg daily) does not count toward this 6‑hour NSAID exclusion. Patients taking only routine cardioprotective ASA remain eligible for NSAIDs, assuming no other contraindications are present. In contrast, therapeutic ASA doses given for suspected cardiac ischemia—typically 160–162 mg or the multi‑tablet doses administered under CACC direction—do count as NSAID use and therefore contraindicate paramedic NSAID administration.

Beyond the directive language, there is important pharmacologic rationale supporting this rule:

• Non‑aspirin NSAIDs, especially ibuprofen, can interfere with aspirin’s irreversible platelet inhibition if taken beforehand. This interaction is timing‑dependent and may reduce ASA’s cardioprotective effect. The FDA recommends that, for patients taking immediate‑release ASA, ibuprofen should be taken ≥30 minutes after or ≥8 hours before ASA ingestion. No safe timing interval has been identified for enteric‑coated ASA.
• Combining NSAIDs with aspirin or other antiplatelet agents increases bleeding risk and is associated with higher rates of major adverse cardiovascular events (MACE), even with short‑term NSAID exposure. Contemporary cardiology guidelines therefore recommend avoiding non‑aspirin NSAIDs in patients with known or suspected cardiac ischemia whenever possible.

These considerations align with the medical directives: ischemic chest pain itself is a contraindication to ketorolac, and the added pharmacologic risks reinforce avoiding NSAIDs in any patient who may have acute coronary syndrome or who has received therapeutic ASA.

Therefore:

• If a patient has taken only their routine 81 mg daily ASA, NSAID analgesia (ketorolac or ibuprofen) remains permissible under the directive.
• If the patient has taken 160–162 mg ASA or the CACC-administered chest‑pain ASA dose within 6 hours, NSAIDs are contraindicated.
• In such cases, acetaminophen is the appropriate analgesic option.

This approach is consistent across Ontario’s directives and with contemporary cardiology guidance, both of which emphasize minimizing NSAID exposure in patients with suspected ischemia or those receiving antiplatelet therapy due to the potential for increased harm.