Anti-Inflammatories
Anti-inflammatory Medicines
Anti-inflammatory medicines are medicines which block the body's natural immune response.
antihistamines
Antihistamines are a broad category of drugs that work to block the action of a molecule found naturally in your body called histamine.
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 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?
Dexamethasone
Dexamethasone is used for immune suppression in a range of diseases and disorders such as: dermatitis, eczema, asthma, leukaemia, emphysema, arthritis, rheumatic fever and COVID-19.
Your immune system normally works to protect you from harmful substances such as bacteria or viruses. If your body detects these things inside it, your immune system will be activated and attack any cells which have been affected by the disease. To ensure that the immune system doesn't go overboard and attack too many healthy cells, your body naturally produces a steroid hormone called cortisol. Cortisol is produced by the adrenal glads and travels through the blood into all areas of your body. Cortisol travels passively across cell membranes and binds to a receptor called the glucocorticoid receptor. When cortisol binds to the glucocorticoid receptor, the receptor is activated. When the glucocorticoid receptor is activated, it causes the cell to produce anti-inflammatory proteins, thus regulating the immune response and keeping you safe.
Some conditions, such as allergic responses and COVID-19, cause the immune system to over-react and attack healthy cells. Many of the diseases that dexamethasone is used to treat involve some aspect of the immune system working inappropriately to attack the body's cells. Dexamethasone is used to reduce the activity of the immune system.
Dexamethasone works by mimicking cortisol and binding to the glucocorticoid receptor. When dexamethasone binds to the glucocorticoid receptor, just as it does when cortisol binds, the glucocorticoid receptor is activated. The cell produces anti-inflammatory proteins and the immune response is lessened.
Check for understanding: Draw a diagram of this process of immune regulation.
Examine the 3D models and skeletal representations of cortisol and dexamethasone below. Can you see any similarities or differences? Can you see how they might be able to bind to the same receptor in the body?
Cortisol
Cortisol is a steroid hormone in your body.
It regulates metabolism, immune function and inflammation by binding to the glucocorticoid receptor.
Cortisol is made by your adrenal glands and transported around the body in the blood.
Almost every cell in your body contains receptors for cortisol.
Steroid hormones act on receptors inside the cell and are able to cross the cell membrane passively.
dexamethasone
Dexamethasone is used to relieve (decrease) inflammation in the body.
Dexamethasone also binds to the glucocorticoid receptors which exist inside almost every cell in your body.