Although ASA administered prior to EMS arrival, consider delivering 160mg dose as per Cardiac Ischemia Medical Directive. See SWORBHP Tip of the Week (May 8, 2017) & OBHG Companion Document (July 2017) "ASA is a safe medication with a wide therapeutic index (the effective dose without side effects can be from 80 – 1500 mg). The additional dose provided by paramedics will not exceed the therapeutic dose while ensuring the correct administration of correct dose of the medication we know saves lives in Acute MI (23% reduction in mortality in the ISIS-2 trial, 1988).
ISIS-2 Collaborators. Randomized trial of intravenous streptokinase, oral aspirin, both, or neither among 17,187 cases of suspected acute myocardial infarction: ISIS-2. Second International Study of Infarct Survival. 1988. Lancet. Aug 13;2(8607):349-60.