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.
Most people feel relief from pain within an hour after taking ibuprofen (with the correct dose). Since NSAIDs should be taken no more frequently than every 6-8 hours, acetaminophen is an acceptable medication to use if symptoms do not improve with the ibuprofen dose.