I took dayquil 3 hours ago for sinus congestion and cough, it has not helped. when is it safe to take a 12 hour claritin (loratadine) d ?

Four Hours: I would say it is safe to take it after 4 hours of the Dayquil. I hope you are feeling better.

4-6 hours usually: Check the instructions on your bottle of Dayquil and find out the suggested interval between doses. You can safely take Claritin (loratadine) D any time after that interval. You can also take Robitussin DM or Delsym for cough simultaneously. Make sure you aren't duplicating any individual ingredients. The number one problem with multi-symptom OTC meds is inadvertent overdosing!