How long do you have to wait after taking tylenol (acetaminophen) to take ibprofrin to break an infants fever?

At least 3 hours: Tylenol (acetaminophen) should be given every 4-6 hours and Ibuprofen every 6-8 hours. For fevers that are particularly difficult to reduce--fever itself does not cause brain damage, except to the anxious parents, except if very high (106-107) for a prolonged period--one could alternate the two every 3 hours for a short period (ie 12 hours of time). If not improving, see the child's doctor.

Infant with fever: For infants under two months, please consult your pediatrician. Fever can signal a dangerous infection. For older babies, fevers can help them fight off infection and need not be treated if the child is otherwise comfortable.