Question: In a patient with an allergic reaction or anaphylaxis, who is experiencing nausea or vomiting, is it okay to treat them with Gravol after I have administered Benadryl?
Great question and thanks for bringing this forward.
Recently the SWORBHP Medical Council has discussed this very topic. Paramedics should not administer Dimenhydrinate and Diphenhydramine to the same patient.
The main concern here would be a cumulative effect from both medications which could result in an anticholinergic excess clinical toxidrome: dry mouth, mild hyperthermia, tachycardia, dilated pupils, CNS changes (confusion/sedation or paradoxical excitation even seizure).