Promethazine, Phenergan - Online Guide
July 21, 2008 – 11:11 am
Advices:
Promethazine, Phenergan is used in relieving allergy symptoms, including hives and nasal congestionprevent and control pain and nausea during and after surgery. It is also used to help produce light sleep, and for the prevention of motion sickness. Promethazine is a phenothiazine antihistamine. It works by blocking the sights where histamine acts.
Phenergan, Promethazine, tablets and elixir contain the active ingredient promethazine, which is a type of medicine called a sedating antihistamine. It works by preventing the actions of histamine.
Histamine is a substance produced by the body as part of its defence mechanisms. It causes the symptoms of allergic reactions. These can include inflammation of the airways or skin, nasal congestion, narrowing of the airways, rashes, and itching of the skin, eyes or nose. Promethazine blocks histamine from binding to its receptors in various parts of the body and this stops it causing the symptoms of an allergic reaction.
Histamine may be released from and act in a small (localised) area of the body such as the nose. Alternatively, histamine can cause more serious, sometimes life-threatening reactions such as anaphylaxis. Promethazine is used for treating localised allergies such as hay fever and nettle rash, as well more serious allergic reactions such as anaphylaxis.
Promethazine also blocks histamine receptors in an area of the brain called the vomiting centre. The vomiting centre is responsible for causing feelings of sickness and for the vomiting reflex. It is activated when it receives nerve messages from the vestibular apparatus in the middle ear.
The vestibular apparatus provides constant feedback to the brain about our body position. When something disturbs the vestibular apparatus, such as movements of the head when travelling by boat or car, nerve signals are sent from the vestibular apparatus to the vomiting centre. This can cause the symptoms of motion sickness, such as nausea, dizziness or spinning sensations (vertigo) and vomiting. Promethazine can be used to prevent motion sickness, because by blocking the histamine receptors in the vomiting centre, it prevents disturbances in the middle ear from activating the vomiting centre.
Promethazine is known as a sedating antihistamine because it enters the brain in significant quantities and causes drowsiness. This effect of the medicine is used to produce sedation before minor procedures or surgery, and can also be used to provide short-term help for people with sleeping difficulties (insomnia).