1. something that is to happen or has happened to a particular person or thing; lot or fortune. 2. the predetermined, usu. inevitable, course of events. 3. the power or agency that determines the course of events.
Alternating between ibuprofen and acetaminophen every 2 hours because you have to wait 4 hours for each of them to take a second dose of the same thing. So instead you take a dose of Acetaminophen now, then Ibuprofen in 2 hours and back to Acetaminophen 2 hours later as needed.
If you use ibuprofen occasionally, there is only a minimal risk that the ibuprofen will interfere with the effect of low-dose aspirin. If you need only a single dose of ibuprofen, take it eight hours before or 30 minutes after taking a regular (not enteric-coated) low-dose aspirin.