Sedating antihistamines over the counter
These could include pain relievers or decongestants.Many of the brand names above are for these combination medicines.Two types of OTC antihistamines are available: first-generation and second-generation. First-generation antihistamines are sometimes used in OTC . Antihistamines prevent histamines from attaching to your cells and causing symptoms.These were some of the first antihistamines scientists developed. They also work in the part of the brain that controls . One of the most common side effects of first-generation antihistamines is feeling sleepy.Antihistamines make your sleepy by antagonizing central histimine-1 (H-1) receptors in the brain.
Drowsiness is one of the major side effects of some antihistamines, such as diphenhydramine (Benadryl) and doxylamine succinate (the antihistamine found in Nyquil).
(There are other types of antihistamines that affect H-2, H-3, and H-4 receptors.) People build up tolerance to them over time and when they stop taking them experience rebound insomnia.
Also called histamine antagonists, antihistamines are administered to fight allergic reactions, in which cases sleepiness is considered a possibly undesirable side effect.
For people who need to get to sleep, however, the drowsiness is the main benefit of antihistamines.
These are usually not prescription drugs and can be purchased at retailers over-the-counter.
Here, the histamines induce an inflammatory response — they dilate the blood vessels, increasing blood flow to the site of injury or invasion.