Antihistamines — First Generation
What Are First Generation Antihistamines?
If you haven't read the first article on how antihistamines work, I highly recommend reading it before reading the rest of this article. You can find it HERE
Antihistamines are a group of medications that block the effects of histamine within your body.
Specifically first generation antihistamines are called so because they were discovered and created before the newer, second generation antihistamines. The first generation antihistamines you are likely to see are:
Diphenhydramine = Benadryl
Meclizine = Antivert
Hydroxyzine = Vistaril or Atarax
Promethazine = Phenegran
These medications can help with symptoms one typically experiences with allergies like itchiness, congestion, sneezing etc as well as motion sickness
Side Effects To Look Out For
One important thing to know about this class of medications is they cross something known as the blood brain barrier (BBB), which is a magical barrier that doesn't allow molecules to go from your blood into the neurons of your brain. Because these medications are able to cross the BBB, they will effect different aspects of your brain (which is why they help with motion sickness).
The single most important side effect, that is sometimes used as an actual effect, is first generation antihistamines will make you very tired. If you're familiar with the brand ZzzQuil, it is actually just the generic form of Benadryl (diphenhydramine), that is useful as a sleep agent.
They also can block specific receptors called muscarinic receptors in the brain that can make you goofy especially in the elderly patients, so it's important that if grandma has signs of dementia, make sure to check her medication list that she's not on any first generation antihistamines
These also block the effects of another type of receptor, called alpha 1 receptors, which can make you lightheaded and dizzy, so be careful about this as well.
As always, before you start any new medications even if they're over the counter, please consult your local health care provider.
Stay tuned for the next article where we will be discussing second generation antihistamines.
