Promethazine is an over-the-counter medicine that’s also available on prescription under multiple brand names. It is primarily an antihistamine that’s used to alleviate allergic symptoms such as itchy eyes and runny noses. However, as it also has a mild sedative effect, it may help to treat short term sleep disorders such as temporary insomnia, or ease feelings of nausea caused by pregnancy or long distance travel.
How Promethazine Works
Promethazine is an active ingredient that’s derived from a group of antipsychotic medications known as Phenothiazines. It works by interacting with the messengers that tell the body to produce histamine so that less of the substance is released, minimising the risk of allergic symptoms when exposed to common triggers like pollen or dog hair.
However, other messenger pathways are also affected by Promethazine, limiting communications between the body and the brain. This is what causes the sleepy, drowsy feeling, and what helps to relax the muscles. When the stomach muscles especially are relaxed, it may help to prevent vomiting and provide a calming effect.
Promethazine is often prescribed to treat:
- Allergies including hayfever
- Allergy symptoms such as hives or a runny nose
- Short term insomnia
- Sleep disturbances caused by coughs or colds
- Nausea, including travel sickness
- Morning sickness in pregnant women
If you have been prescribed Promethazine, it is important to take the medicine as advised by your doctor. If taking an over-the-counter variant, follow dosing instructions on the packaging. This may typically range from 20mg to 100mg depending on the reason for taking the medicine. Promethazine should be taken at different times of day depending on the reason for the treatment. For insomnia, Promethazine is best taken 20 minutes before bedtime. For travel sickness, 1-2 hours before starting the journey.
Promethazine Side Effects
Promethazine is generally considered to be safe when taken as prescribed, or as recommended on the packaging. In some cases, it may be safe for children. However, as with many medications, some patients may experience mild side effects, including:
- Daytime sleepiness and drowsiness
- Reduced awareness / confusion
- Dry mouth
- Vivid dreams
- Visual disturbances
It is important for patients to read the patient information leaflet in the packaging for a full list of possible side effects from taking Promethazine. Always consult with your doctor if side effects persist. If experiencing difficulty breathing, call 999 immediately.
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