Antihistamines are those drugs that block the H1 histamine receptors and not the other histamine receptors like H2, H3 and H4. These drugs act by block the histamine-induced responses in allergic reactions.It is the most widely used allergy medicine for most of the common allergic diseases.The anticholinergic effect also helps with nasal and bronchial secretions, in preventing nausea and vomiting (including motion sickness and vomiting associated with pregnancy), vestibular disturbances and in treatment of drug-induced movement disorders.Doxepin is an antihistamine with additional antidepressant actions.Understanding the mechanism for opioid-induced nausea will aid in the selection of appropriate agents.
Strategies to minimize adverse effects of opioids include dose reduction, symptomatic management, opioid rotation, and changing the route of administration.
6 Antihistamine medications block or reduce histamine-mediated effects at one of four identified histamine receptors (see Table 1 below).
These include the first-generation H1 antagonists, or sedating antihistamines (eg, diphenhydramine, chlorpheniramine), and second-generation H1 receptor blockers, or nonsedating antihistamines (eg, loratadine, cetirizine).
Antihistamines aren't only used for allergies, however.
Some are more commonly used to treat nausea and vomiting, such as Cyclizine (the main ingredient in Valoid), while others are prescribed to patients battling with insomnia, or as an appetite stimulant.