What is Phenergan?
Phenergan is a drowsy antihistamine medication that contains the active ingredient promethazine hydrochloride.
What is Phenergan used for?
Phenergan is used to treat a variety of different conditions, including:
- Temporary sleeplessness in adults (insomnia)
- Hay fever and other minor allergic reactions
- Travel sickness, nausea and vomiting
- Coughing and a runny nose
How does Phenergan work?
Histamine is a substance that the body releases when it detects something harmful, such as an infection. When histamines are released, your blood vessels expand and your skin swells, which helps to protect the body from infection.
For people with allergies, however, the body believes certain substances are harmful that aren’t to others, and releases histamine as a result. This causes the classic symptoms of allergic reactions, such as a skin redness, hives, itching and swelling.
Promethazine hydrochloride, the active ingredient in Phenergan, is an antihistamine. It blocks the effects of histamine, which reduces the symptoms of mild allergic reactions such as hay fever.
In addition to reducing the symptoms of hay fever, promethazine has a number of other effects. It makes you drowsy, which means it can be used to treat temporary difficulties sleeping. It also affects the area of the brain that controls vomiting, which means it can be used to treat feelings of sickness - especially while travelling.
How long does Phenergan take to work?
Phenergan acts quite quickly. You should begin to notice the effects of the treatment around 20 minutes after taking it.
How long does Phenergan last?
The effects of Phenergan can last between 12 and 24 hours.
How should I take Phenergan?
Adults should take one tablet daily, preferably at night.
You should only take Phenergan when you need it, for example when you’re struggling to sleep due to temporary anxiety or your hay fever symptoms.
Who can’t take Phenergan?
Most adults can take Phenergan on a temporary basis safely. However, it isn’t suitable for everyone. Tell your GP or a pharmacist before taking Phenergan if you:
- Have had an allergic reaction to promethazine or any other medicine in the past
- Have primary angle closure glaucoma
- Have problems urinating or emptying your bladder
- Have epilepsy or any other condition that causes seizures
- Are intolerant of any sugars
- Have an upcoming allergy test
- Are unable to drink alcohol
- Are trying to get pregnant
Does Phenergan cause any side effects?
Some people will experience mild side effects while taking Phenergan. They may include:
- Daytime tiredness
- Difficulty concentrating
Phenergan sometimes makes your skin more sensitive to sunlight. Keep out of direct or strong sunlight and follow sun safety advice.
People aged 65 and above who take Phenergan may experience additional side effects. These include:
- Dry mouth
- Blurred vision
- Difficulty passing urine
In rare instances, Phenergan may cause more serious side effects. Stop taking Phenergan and seek immediate medical attention if you have:
- Signs of liver problems, such as yellowing skin or whites of the eyes
- Bruising or bleeding that’s worse than normal
- Muscle stiffness, shaking, or unusual face or tongue movements
- Signs of a serious allergic reaction, such as difficulty breathing, chest tightness, wheezing, a skin rash, or swelling of the mouth, face, lips, tongue or throat
How should I store Phenergan?
Phenergan should be stored in a dry, cool environment that does not exceed 25°C.
Always read the patient information leaflet before commencing treatment.
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Content last updated:
25 Oct 2023