Stemetil tablets, syrup and injection all contain the active ingredient prochlorperazine, which is medicine with two quite different uses. In lower doses it is used for nausea and vomiting, while in higher doses it is used in psychiatric illnesses.

What is Stemetil used for?

In adults, Stemetil is used for the conditions below.

  • Treating and preventing feelings of sickness and vomiting due to any cause.
  • Relieving nausea, vomiting and attacks of dizziness or spinning sensations (vertigo) associated with Meniere's disease and other inner ear disorders such as labyrinthitis.
  • Long-term management of psychotic illness such as schizophrenia.
  • Short-term treatment of acute mania.
  • Short-term treatment of severe anxiety.

In children aged over one year and weighing more than 10kg, Stemetil tablets or syrup may be used for:

  • Treating and preventing feelings of sickness and vomiting due to any cause.

How does Stemetil work?

  • Stemetil tablets, syrup and injection all contain the active ingredient prochlorperazine, which is a type of medicine called a phenothiazine. Prochlorperazine is also available without a brand name, ie as the generic medicine.
  • When used in psychiatric illness, prochlorperazine is sometimes described as a neuroleptic or a 'major tranquilliser'. However this last term is fairly misleading, as this type of medicine is not just a tranquilliser, and any tranquillising effect is not as important as its main mechanism of action in psychiatric illness.
  • Prochlorperazine works by blocking dopamine receptors in the brain. Dopamine is a natural compound called a neurotransmitter, and is involved in transmitting messages between brain cells. Dopamine is a neurotransmitter known to be involved in regulating mood and behaviour, amongst other things. Psychotic illness, and particularly schizophrenia, is thought to be caused by overactivity of dopamine in the brain. Prochlorperazine blocks the receptors that dopamine acts on, and this prevents the overactivity of dopamine in the brain. This helps to control psychotic illness.
  • Prochlorperazine also affects dopamine receptors in an area of the brain that controls nausea and vomiting. Vomiting is controlled by an area of the brain called the vomiting centre. The vomiting centre is responsible for causing feelings of sickness (nausea) and for the vomiting reflex. It is activated when it receives nerve messages from another area of the brain called the chemoreceptor trigger zone (CTZ) and when it receives nerve messages from the gut.
  • Prochlorperazine controls nausea and vomiting by blocking dopamine receptors found in the CTZ. This stops the CTZ from sending the messages to the vomiting centre that would otherwise cause nausea and vomiting.

How do I take Stemetil?

  • Prochlorperazine can be taken either with or without food.
  • The dose of this medicine that is prescribed and how often it needs to be taken depends on the condition being treated. It is important to follow the instructions given by your doctor. These will be printed on the dispensing label that your pharmacist has put on the medicine.
  • If you forget to take a dose take it as soon as you remember, unless it is nearly time for your next dose. In this case just leave out the forgotten dose and take the next dose as usual. Don't take a double dose to make up for a missed dose.
  • If you have been taking high doses of this medicine for a long time, for example to treat schizophrenia, you should not suddenly stop taking it unless your doctor tells you to, even if you feel better and think you don't need it any more. This is because the medicine controls the symptoms of the illness but doesn't actually cure it. This means that if you suddenly stop treatment your symptoms could come back. Stopping the medicine suddenly may also rarely cause withdrawal symptoms such as nausea, vomiting, difficulty sleeping or tremor. When long-term treatment with this medicine is stopped, it should be done gradually, following the instructions given by your doctor.

Stemetil should not be used in

  • Children (except for the management of sickness and vomiting - see above).
  • Breastfeeding.
  • This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Stemetil should be used with caution in

  • Elderly people.
  • People with liver or kidney problems.
  • Elderly people with dementia. (Medicines of this type have been shown to increase the risk of stroke in this group of people. Prochlorperazine is not licensed or recommended for treating behavioural disturbances in elderly people with dementia).
  • People with risk factors for having a stroke, for example a history of stroke or mini-stroke (TIA), smoking, diabetes, high blood pressure, or a type of irregular heartbeat called atrial fibrillation.
  • People with a personal or family history of blood clots (venous thromboembolism), for example in a vein of the leg (deep vein thrombosis) or in the lungs (pulmonary embolism).
  • People with other risk factors for getting a blood clot, for example smoking, being overweight, taking the contraceptive pill, being over 40, recent major surgery or being immobile for prolonged periods.
  • Heart disease.
  • People with a slow heart rate (bradycardia).
  • People with a personal or family history of an abnormal heart rhythm seen on a heart monitoring trace (ECG) as a 'prolonged QT interval'.
  • People with low levels of potassium, calcium or magnesium in their blood (hypokalaemia, hypocalcaemia or hypomagnesaemia).
  • People who are malnourished.
  • People who are dehydrated, eg due to severe diarrhoea or vomiting, or treatment with diuretic medicines.
  • Diabetes. People with diabetes should monitor their blood sugar levels more closely while taking this medicine. This medicine may increase the blood sugar levels in the body.
  • Underactive thyroid gland (hypothyroidism).
  • Tumour of the adrenal gland (phaeochromocytoma).
  • Enlarged prostate gland (prostatic hypertrophy).
  • Abnormal muscle weakness (myasthenia gravis).
  • People with a history of seizures (fits) eg epilepsy.
  • People with conditions that increase the risk of epilepsy or convulsions, eg brain damage or withdrawal from alcohol.
  • Parkinson's disease.
  • History of closed angle glaucoma.
  • People with a history of a drop in the normal number of white blood cells in the blood.
  • People who are allergic to other phenothiazine medicines, eg chlorpromazine, trifluoperazine.

Can I take Stemetil while pregnant or breastfeeding?

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine during pregnancy has not been established. It should not normally be used in pregnancy, particularly in the first and third trimesters, unless considered essential by your doctor. However, doctors may sometimes prescribe this medicine to treat severe nausea and vomiting in pregnancy (hyperemesis gravidarum), or to treat pregnant women with severe psychiatric illness. If you are pregnant and your doctor has prescribed you this medicine, it is because the condition being treated with the medicine could pose more of a risk to the baby than the medicine itself. However, if the medicine is used during the third trimester it could cause side effects or withdrawal symptoms in the baby after birth and the baby may need extra monitoring because of this. If you are concerned or want any further information you should talk to your doctor or pharmacist.
  • If you think you could be pregnant while taking this medicine it is important to consult your doctor straight away for advice. If you have been taking the medicine for long periods of time, for instance to treat schizophrenia, you should not suddenly stop taking it unless your doctor tells you to, as this could cause your symptoms to come back.
  • This medicine may pass into breast milk. As it could cause drowsiness and potentially other side effects in a nursing infant, it is recommended that women who need long-term treatment with this medicine should not breastfeed. However, if you are taking this medicine for a short period of time to treat nausea and vomiting it appears that breastfeeding during the treatment poses little risk to a nursing infant. Ask your doctor for further medical advice before breastfeeding while taking this medicine.

What are the possible side effects of Stemetil?

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

  • Abnormal movements of the hands, legs, face, neck and tongue, eg shakiness, twitching, rigidity.
  • Anxiety, restlessness and agitation (akathisia).
  • Rhythmical involuntary movements of the tongue, face, mouth and jaw, which may sometimes be accompanied by involuntary movements of the arms and legs. This is called tardive dyskinesia. You should tell your doctor straight away if you get any of these symptoms.
  • A drop in blood pressure that occurs when moving from a lying down or sitting position to sitting or standing, which results in dizziness and lightheadedness (postural hypotension - see important information section above).
  • Drowsiness.
  • Dry mouth.
  • Difficulty sleeping (insomnia).
  • Skin rashes.
  • Stuffy nose.
  • Increased sensitivity of the skin to UV light (photosensitivity - see important information section above).
  • Interference with the body's temperature regulation (this is more common in elderly people and can cause heat stroke in very hot weather or hypothermia in very cold weather).
  • Decrease in the numbers of a type of white blood cell (neutrophil) in the blood (neutropenia) - see important information section above.
  • Sudden severe deficiency in the number of white blood cells in the blood (agranulocytosis).
  • Abnormal heart beats (arrhythmias).
  • Jaundice (tell your doctor straight away if you notice any yellowing of your eyes or skin while taking this medicine).
  • High blood prolactin (milk producing hormone) level (hyperprolactinaemia). Rarely this may lead to symptoms such as breast enlargement, production of milk, stopping of periods or problems getting an erection.
  • High temperature combined with falling levels of consciousness, paleness, sweating, muscle stiffness and a fast heart beat (neuroleptic malignant syndrome). Requires stopping the medicine and immediate medical treatment - tell your doctor immediately if you experience these symptoms.
  • Blood clots in the veins especially in the legs (symptoms include swelling, pain and redness in the leg), which may travel through blood vessels to the lungs causing chest pain and difficulty in breathing. If you notice any of these symptoms seek medical advice immediately.

Can I take Stemetil with other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.

There may be an increased risk of drowsiness and sedation if prochlorperazine is taken with any of the following (which can also cause drowsiness):

  • alcohol
  • barbiturates, eg amobarbital, phenobarbital
  • benzodiazepines, eg diazepam, temazepam
  • MAOI antidepressants, eg phenelzine
  • sedating antihistamines, eg chlorphenamine, hydroxyzine
  • sleeping tablets, eg zopiclone
  • strong opioid painkillers, eg morphine, codeine
  • tricyclic antidepressants, eg amitriptyline.

This medicine may enhance the blood pressure-lowering effects of certain medicines used to treat high blood pressure (antihypertensives). If you are taking medicines for high blood pressure you should tell your doctor if you feel dizzy or faint after starting treatment with this medicine, as your blood pressure medicines may need adjusting.

There may be an increase in side effects such as dry mouth, constipation, confusion or heat stroke (in hot and humid conditions) if prochlorperazine is taken with other medicines that have anticholinergic effects, such as the following:

  • anticholinergic medicines for Parkinson's symptoms, eg procyclidine
  • antihistamines, eg brompheniramine, chlorphenamine
  • antipsychotic medicines
  • other antisickness medicines, eg promethazine, meclozine, cyclizine
  • antispasmodic medicines, eg hyoscine
  • MAOI antidepressants, eg phenelzine
  • medicines for urinary incontinence, eg oxybutynin, flavoxate, tolterodine, propiverine, trospium
  • muscle relaxants, eg baclofen
  • tricyclic antidepressants, eg amitriptyline.

Prochlorperazine should be avoided in people taking medicines that increase the risk of a type of abnormal heart rhythm, seen as a 'prolonged QT interval' on an ECG. These medicines include the following:

  • antiarrhythmics (medicines to treat abnormal heart beats), eg amiodarone, procainamide, disopyramide, sotalol , dronedarone
  • the antihistamines astemizole, mizolastine or terfenadine
  • arsenic trioxide
  • atomoxetine
  • certain antidepressants, eg amitriptyline, imipramine, maprotiline
  • certain antimalarials, eg halofantrine, chloroquine, quinine, mefloquine, Riamet
  • certain antipsychotics, eg thioridazine, chlorpromazine, sertindole , droperidol
  • cisapride
  • intravenous erythromycin or pentamidine
  • methadone
  • moxifloxacin
  • saquinavir.

There may also be an increased risk of a prolonged QT interval if medicines that can alter the levels of salts such as potassium or magnesium in the blood, eg diuretics such as furosemide, are taken in combination with prochlorperazine.

There may be an increased risk of a drop in the number of white blood cells in the blood if prochlorperazine is taken in combination with other medicines that can have this side effect, such as the following:

  • anti-cancer chemotherapy medicines
  • carbamazepine
  • co-trimoxazole
  • penicillamine
  • phenylbutazone
  • sulphonamides, eg sulfadiazine.

There may be an increased risk of side effects if this medicine is used in combination with any of the following medicines:

  • lithium
  • metoclopramide .
  • Prochlorperazine may oppose the effects of dopamine agonists used to treat Parkinson's disease, eg levodopa.
  • Prochlorperazine may oppose the effect of anticonvulsant medicines used to treat epilepsy.
  • Prochlorperazine should not be taken by people receiving treatment with desferrioxamine.