In addition to this antihistamine effect, they can have parallel pharmacological properties, for example antimuscarinic and adrenolytic effects which must be considered.
It is usual to classify H1-antihistamines into two classes: old ones, called first-generation agents, which are sedating and recent ones, called second-generation agents which have slight or no sedating effects because they do not cross the blood-brain barrier.
Due to their safety and improved effectiveness, they have largely replaced barbiturates as drugs of choice in the treatment of anxiety.
Common side effects include sedation, carbohydrate craving, and weight gain.
Weight gain with TCAs can be substantial, averaging 1 to 3 pounds per month of treatment.
In addition, most analgesic-hypnotic combination medications (“” preparations) contain diphenhydramine.
Second-generation nonsedating antihistamine drugs are used primarily for treatment of seasonal, environmental, and other allergic reactions and are not used for the treatment of insomnia.-receptor blockade.