Claratyne
how do antihistamines work?
Antihistamines are a broad category of drugs that work to block the action of a molecule found naturally in your body called histamine.
They work by binding to histamine receptors, preventing the receptors from being activated, and stopping the immune response. Scroll down to read more about the roles of the individual molecules.
histamine
This molecule exists naturally in your body.
It is involved in local immune responses.
Histamine is produced by immune cells when they detect any injury to your body.
Histamine binds to histamine receptors. Histamine receptors are located on the cell membrane of many different body cells, such as smooth muscle cells.
When the histamine receptor is activated, this causes white blood cells (more immune cells) and immune proteins to come towards the injured site, so that it can be treated.
Like many molecules in your body, histamine has many different roles.
In the brain, histamine is a neurotransmitter which is involved in regulating sleep.
loratadine
Loratadine is a second-generation antihistamine.
It blocks histamine receptors, stopping the histamine receptors from being activated, and preventing the immune (allergic) reaction from starting.
The loratadine molecule is too large to enter the brain, and as such it does not cause drowsiness as many other antihistamine medications do.
promethazine
Promethazine is a first-generation antihistamine.
It blocks histamine receptors, stopping the histamine receptors from being activated, and preventing the immune (allergic) reaction from starting.
Its smaller size means that it is easily absorbed into the brain, so that it causes size effects such as drowsiness.
As such, promethazine can be used to treat insomnia.
Why do you think patients with allergies might not want to take promethazine regularly?