Phenergan contains promethazine, a sedating antihistamine. It is used for allergic conditions and itching, for nausea, vomiting and motion sickness, and for its strong drowsiness-causing effect. It comes as 10 mg and 25 mg tablets, a cream and an injection. It must never be given to children under two.
What is Phenergan?
Phenergan is registered in South Africa in several forms:
| Product | Contains | Schedule |
|---|---|---|
| Phenergan tablet | Promethazine 10 mg | S2 |
| Phenergan tablet | Promethazine 25 mg | S2 |
| Phenergan cream | Promethazine 2 g/100 g | S2 |
| Phenergan injection | Promethazine 25 mg/ml | S5 |
Promethazine is a first-generation antihistamine of the phenothiazine family. It blocks histamine H1 receptors — useful in allergy — but also acts on several other receptor types, and those extra actions explain most of what it does:
| Receptor blocked | Effect |
|---|---|
| Histamine H1 | Reduces allergic symptoms and itching |
| H1 in the brain | Marked drowsiness and sedation |
| Dopamine | Reduces nausea and vomiting |
| Muscarinic | Dry mouth, blurred vision, constipation, urinary retention |
Crossing into the brain is the key difference from modern antihistamines. Newer ones such as cetirizine and loratadine were designed to stay out of the brain, treating allergy without heavy sedation. Promethazine does the opposite — and its sedation is often the reason it is chosen rather than a drawback to tolerate.
Promethazine is the same ingredient found in many South African combination cough and pain syrups, usually alongside paracetamol and codeine. If you are taking one of those, you are taking promethazine too — check before adding Phenergan on top. See the promethazine guide for more on the ingredient itself.
What is Phenergan commonly used for?
- Allergic conditions — hay fever, allergic rhinitis, hives and allergic skin reactions.
- Itching, including from eczema, insect bites and chickenpox, where the sedation also helps sleep.
- Nausea and vomiting, including in some post-operative settings.
- Motion sickness, taken before travel rather than once symptoms start.
- Vertigo and inner-ear-related nausea.
- Short-term sedation, including before minor procedures.
- Localised itching and insect bites, using the cream.
For daytime allergy control in someone who needs to drive, work or study, a non-sedating antihistamine is almost always better. Phenergan suits situations where sedation is acceptable or actively wanted — night-time itching being the classic case.
A note on the cream. Topical antihistamine creams are widely sold but are of limited value, and applying an antihistamine to skin can itself cause an allergic contact dermatitis — an itchy rash from the treatment, easily mistaken for the original problem worsening. For most itchy rashes a topical steroid or a simple emollient is more effective. Do not apply it to broken or extensively damaged skin, where absorption increases unpredictably.
It treats symptoms, not causes, and has no effect on infection.
How Phenergan fits into this medicine category
| Group | Examples | Notes |
|---|---|---|
| Sedating antihistamines | Promethazine (Phenergan), chlorphenamine | Allergy, itch, nausea; marked drowsiness |
| Non-sedating antihistamines | Cetirizine, loratadine | Allergy without significant sedation |
| Anti-nausea (dopamine blockers) | Metoclopramide | Nausea and vomiting |
| Benzodiazepines | Diazepam | Anxiety, muscle spasm; controlled |
| Tricyclics | Amitriptyline | Nerve pain, mood, sleep |
| Anti-epileptics | Carbamazepine | Seizures, some nerve pain |
Promethazine sits across several of these roles, which is why it appears in such different products. See the mental health, nerve and neurological medicines hub.
What to check before using Phenergan
Never give promethazine to a child under two years old. This is an absolute restriction, not a precaution — it has caused fatal respiratory depression in very young children. Be especially careful with combination syrups marketed for children’s cough or pain, where promethazine is not always prominent on the front of the pack.
Check whether anything else you take contains promethazine, paracetamol or codeine.
Speak to a pharmacist or doctor first if you:
- Are giving it to any child, where age and weight determine suitability.
- Are elderly. Sedation, confusion, falls and urinary retention are all more likely, and this class is best avoided in older people.
- Have breathing problems — asthma, COPD or sleep apnoea.
- Have glaucoma, particularly narrow-angle.
- Have prostate enlargement or difficulty passing urine.
- Have epilepsy.
- Have liver or kidney disease.
- Have heart rhythm problems, or take medicines affecting the QT interval.
- Take any other sedating medicine — opioids, benzodiazepines, sleeping tablets — or alcohol.
- Take an MAOI antidepressant.
- Are pregnant or breastfeeding.
Do not drive or operate machinery. The sedation is substantial and can persist into the following day.
Possible cautions and when to ask a pharmacist or doctor
Common effects are drowsiness, dry mouth, blurred vision, dizziness, constipation and difficulty passing urine. In children, promethazine sometimes causes the opposite of sedation — restlessness and agitation.
Seek medical attention urgently if you notice:
- Slow, shallow or difficult breathing, or unusual difficulty waking someone — especially a child, or anyone also taking an opioid.
- Muscle stiffness, tremor, restlessness, or uncontrolled movements of the face, tongue or limbs.
- High fever with rigidity, confusion and sweating — a rare but serious reaction.
- A seizure.
- Yellowing of the eyes or skin.
- Swelling of the face, lips or tongue, or difficulty breathing.
- A severe rash or blistering skin.
- Inability to pass urine.
- Palpitations or fainting.
With the cream, stop and seek advice if the treated area becomes more red, itchy or inflamed — that may be a reaction to the cream itself.
Promethazine can increase skin sensitivity to sunlight. Use sun protection during a course.
Promethazine-and-codeine syrups are misused recreationally, sometimes mixed into soft drinks. That combination suppresses breathing, the effect deepens with alcohol or other sedatives, and deaths have resulted. If you or someone you know is using such syrups outside their intended purpose, it is worth raising with a doctor or pharmacist.
See a doctor if allergy symptoms persist, if nausea or vomiting continues beyond a couple of days or comes with severe pain, if you cannot keep fluids down, or if you find yourself relying on it to sleep.
Related medicine guides
- Browse Mental Health, Nerve & Neurological Medicines guides
- Read: Trepiline used for
- Read: Nurika used for
Frequently asked questions
What are Phenergan tablets used for? Allergic conditions and itching, nausea, vomiting and motion sickness, and short-term sedation. They contain promethazine.
What is Phenergan 25 mg used for? The higher tablet strength, used for the same purposes — allergy, itching, nausea and motion sickness — and where more sedation is acceptable.
What is Phenergan cream used for? Localised itching, such as insect bites. Topical antihistamines are of limited value and can themselves cause an itchy rash — a steroid cream or emollient is often better.
Does it make you sleepy? Yes, markedly, and the effect can carry into the next day. Do not drive or operate machinery.
Can I give it to my child? Never under two years old. Above that, ask a pharmacist, and check combination syrups for what else they contain.
Is Phenergan a sleeping tablet? It is not a dedicated sleeping medicine, though the drowsiness is marked and it is sometimes used short-term for that. It is not for long-term use.
Can I drink alcohol with it? No. Alcohol adds substantially to the sedation and to the risk of suppressed breathing.
Can I take it with a cold and flu syrup? Check the label first. Many South African cough and pain syrups already contain promethazine, and doubling up is easy.