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.
There are other times when you might want to switch from one to the other, too. Let's say you gave your child ibuprofen an hour or two ago, and her fever is still high or she's no more comfortable than she was before she took the medicine. In this instance, it's okay to give acetaminophen a try now. In fact, because you can't give her ibuprofen again for six to eight hours after the first dose, it may be helpful to try a new tack. If the acetaminophen does the trick, your child won't need any medication at all for another six to eight hours.