In managing anaphylaxis, when should antihistamines be administered?

In the management of anaphylaxis, antihistamines should be administered only once the patient is stabilized. This is because adrenaline (epinephrine) is the first-line treatment for anaphylaxis due to its rapid action and ability to counteract the severe effects of anaphylaxis, such as airway swelling and cardiovascular collapse. Administering antihistamines immediately or as a first-line treatment does not address the life-threatening nature of anaphylaxis, as they act more slowly and do not provide the necessary immediate relief of symptoms.

Once the patient has been stabilized, and the acute life-threatening symptoms are managed with adrenaline, antihistamines can be given as an adjunct to help alleviate remaining symptoms such as urticaria or itching, but they are not a substitute for adrenaline. Administering antihistamines before intravenous fluids is also not recommended because the priority in anaphylaxis management is to ensure adequate airway and circulation through the use of adrenaline and fluid resuscitation when necessary, rather than focusing on antihistamines which contain slower-reacting properties.

In summary, the appropriate timing for the administration of antihistamines in the context of anaphylaxis is once the patient is stabilized after the critical initial management steps have been taken.