Non sedating h1 antihistamines
The sedating antihistamines are derived from different chemical groups.
Here are some examples: Dimenhydrinate (Gravol) 50-100 mg qid Diphenhydramine (Benadryl) 25-50 mg qid Alkylamines Chlorpheniramine (chlortipalon) 4 mg tid Dexchlorpheniramine 2-4 mg tid Phenothiazines Promethazine (Phenergan) 10-25 mg bid Piperazines Hydroxyzine (Atarax) 10-25 mg tid Piperidines Cyproheptadine (Periactin) 4 mg tid Azatadine (Zadine) 1-2 mg tid Unwanted effects are common with these antihistamines, the commonest being sedation, dizziness fatigue, insomnia and dry mouth. Alcohol increases the sedative effects of these drugs and users are advised to abstain from drinking while on antihistamine therapy.
The H1 block is useful to treat allergic reactions.
The older sedating antihistamines have been used for years and are cheap and effective.
H2 receptors tend to act as negative feedback receptors and turn the allergic reaction off.
The sedative effects of some foods such as milk and wheat in susceptible people is not blocked, but enhanced by antihistamines.
The classic antihistamines are represented by chlorpheniramine ( Chlor-Tripalon), brompheniramine (Dimetane), diphenhydramine ( Benadryl) and dimenhydrinate (Gravol). These antihistamines have been marketed as allergy preparations for the relief of hay fever and hives and other itchy skin conditions.
To get a good idea of what histamine can do, let us imagine the effects of an injection of a small amount of histamine: Headache is felt as a pulsating, whole-head pain, often with a sense of pressure.
Fast heart, blood pressure falls, irregular beats with alarming palpitations.