Patient/caregiver was instructed upon promethazine and mechanism of action as follows:
- Promethazine is a medication belonging to the antihistamine group, especially used in individuals with complaints of allergy and motion sickness.
- Histamine is a chemical mediator released from the mast cells during an allergy response. Histamine binds to the H-1 receptors on the cells in the body and results in development of symptoms of allergy, such as, itching of the skin, sneezing, runny nose, and increased mucus production in the body.
- Also, acetylcholine is a chemical mediator produced in the body, which acts on receptors called muscarinic receptors, thus contributing to development of symptoms of motion sickness, such as, nausea and vomiting.
- Promethazine blocks the H-1 receptors, thus inhibiting the binding and action of histamine on these receptors and leading to calming down of symptoms of allergy.
- Promethazine also blocks the acetylcholine on the muscarinic receptors, thus suppressing the nausea and vomiting and contributing to the calming down of symptoms of motion sickness.
- Promethazine also has some calming down action on the activity of the brain, as a side-effect to the main actions. This calming down effect of promethazine on the brain results in dizziness and sleep.
