How it works
What does chlorpromazine do?
Chlorpromazine is a ‘first-generation antipsychotic’ (sometimes described as a ‘conventional antipsychotic’).
An antipsychotic medicine helps to adjust the levels of dopamine and other chemicals available in your brain. Chlorpromazine reduces dopamine activity where it is too high, helping with symptoms like hallucinations.
How long will chlorpromazine take to start working?
It can take a few days for chlorpromazine to take effect. It’s difficult to determine how long you can expect to wait, as the medication affects each person differently.
If you have had no change after three to four days of taking chlorpromazine, talk to your doctor. Don’t increase your dose yourself if you think the medication isn’t working.
How long will I need to take chlorpromazine?
Young people usually take chlorpromazine for many months or years. Your doctor should talk to you about how long you might expect to stay on this medication.
Ideally, you should stay on an antipsychotic medication for four to six weeks before deciding whether to continue taking it in the long term. This gives the medication a chance to build up in your system and to begin delivering its full effects.
Your doctor should review your progress on this medication at least once a year.
Your doctor needs to know if...
You need to talk to your doctor or pharmacist before starting treatment with chlorpromazine if any of the following apply to you:
- you have high blood sugar (symptoms include being thirsty all the time, needing to wee often, decrease in appetite and/or feeling weak)
- you have ever had seizures (fits)
- you have Parkinson’s disease
- you have heart problems, or a family history of heart problems including strokes and heart failure
- you have ever had blood clots, or you have a family history of blood clots
- you have myasthenia gravis, with weak or tired muscles that can make it difficult to breathe
- you have an underactive thyroid gland (hypothyroidism)
- you have liver or kidney problems
- you have glaucoma (raised pressure in the eye)
- you have a condition called phaeochromocytoma (high blood pressure caused by a tumour near the kidney)
- you have an enlarged prostate gland
Chlorpromazine may also cause problems for people with certain allergies or intolerances:
- Chlorpromazine tablets contain lactose and may not be suitable for people who have problems eating some sugars or dairy (milk-based) products.
- Chlorpromazine oral syrup contains sorbitol and sugars; methyl, ethyl and propyl parahydroxybenzoates (additives that can cause allergies in some people); and a small amount of alcohol (though not enough to cause a change in your blood levels).
- Chlorpromazine sugar-free oral solution contains: sorbitol and sugars; aspartame (not suitable for people with a condition called phenylketonuria); sunset yellow E110 (an additive causing allergies in some people); and a small amount of alcohol (though not enough to cause a change in your blood levels).
- Chlorpromazine injections contain sulphites that can cause allergies in some people.
There are many manufacturers of liquid chlorpromazine products so talk to your pharmacist if you are concerned about any of chlorpromazine’s ingredients and their potential effects.
You should only take chlorpromazine as agreed with your doctor.
You will get the best effect from chlorpromazine if you take it regularly at the dose prescribed by your doctor.
Make sure that you know your dose. If it's not written on the label, check with your pharmacist or doctor.
Some people start with a low dose of chlorpromazine in liquid form before moving on to tablets as their dose increases.
At the start, you may take chlorpromazine three or four times a day, but as it’s a long-acting drug, you’ll probably be able to avoid taking it during school or college hours.
If you do have to take your medication at school or college, ask your doctor to help you talk to a teacher or school nurse about how best to do this (some people prefer to keep a separate supply of medicine at school or college, for instance - your pharmacist can help with that).
Tablets and liquid can be taken before or after food. Swallow tablets whole with a drink of water – if chewed, they taste horrible!
The liquid medicine can be mixed with your favourite cold drink or added to food, if you prefer.
It’s possible to administer a fast-acting dose of chlorpromazine by injection if you’re having serious symptoms. You must visit a doctor or nurse for this and should stay lying down for 30 minutes after receiving the injection. Your blood pressure will probably be taken during this time, to check it’s within normal levels.
What if I miss a dose?
If you forget to take a dose of chlorpromazine, carry on from the next dose.
Do not take a double dose.
What will happen if I forget to take my chlorpromazine?
If you forget to take this medication for a few days, your old symptoms might start coming back. If this happens, talk to your doctor without delay.
Stopping the use of chlorpromazine
Once you start taking an antipsychotic medication, the brain adjusts to having a new level of dopamine around. If you stop taking the antipsychotic all at once, the balance starts to change again, meaning you could get your old symptoms back.
Stopping this medicine quickly, or reducing the dose too much at once, may also give you ‘kick-back’ symptoms like feeling sick, being sick, shaking, uncontrolled movements of the hands and body, and finding it hard to get to sleep.
You can stop taking chlorpromazine safely and gradually over several days or weeks with your doctor’s help.
The information on this page was reviewed by the College of Mental Health Pharmacy in March 2020.