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Home > Medicines & Drugs > Pentazocine

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Pentazocine

  • Pentazocine is used to treat pain particularly after an operation or during child birth.
  • Nausea, vomiting or constipation may occur with this medicine. Your doctor may be able to prescribe medicines to take with pentazocine to help with these side effects.
  • Pentazocine can cause drowsiness. Make sure your reactions are normal before driving, operating machinery or doing any other jobs which could be dangerous if you were not fully alert.

About pentazocine

Type of medicineAnalgesic
Used forPain
Also calledFortral
Available asTablets, capsules, injection and suppositories

Pentazocine is used to treat severe pain; it works on the nerves and brain to reduce the pain you feel. It can be used to ease pain before, during and after an operation.

Before taking pentazocine

Before taking pentazocine make sure your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breast-feeding.
  • If you suffer from heart, liver, kidney, respiratory (breathing), prostate or thyroid problems.
  • If you suffer from epilepsy, porphyria or hypotension (low blood pressure).
  • If you have recently suffered a serious head injury.
  • If you have been constipated for more than a week, with or without tummy pain and bloatedness.
  • If you currently or have ever suffered from drug or alcohol dependence.

How to take pentazocine

  • Take exactly as directed by your doctor.
  • Never take more than the prescribed dose. If you suspect that you or someone else has taken an overdose of pentazocine contact your doctor or go to the accident and emergency department of your local hospital at once. Always take the container with you, if possible, even if it is empty.

Getting the most from your treatment

  • Alcohol will increase any feelings of drowsiness. Avoid alcoholic drinks.
  • Pentazocine can cause constipation. Constipation can often be eased by eating plenty of fibre, such as wholegrain cereals, fruit, green leafy vegetables and drinking 6-8 glasses of water each day.
  • You may feel sick or be sick while taking pentazocine, especially during the first few days, your doctor may be able to prescribe a medicine to help stop this side effect.
  • Because pentazocine is a controlled drug, if you are planning a trip abroad, check with the government department HM Revenue and Customs to see if you need any documentation for your medicine. HM Revenue and Customs (HMRC) has a list of medicines that contain controlled drugs and can tell you the amount that you are allowed to take abroad. If you need to pack more of your medicine than you are allowed you will need to apply in writing for a licence from the Home Office before you travel.

Can pentazocine cause problems?

Along with their useful effects all medicines can cause unwanted side effects, which usually improve as your body adjusts to the new medicine. Speak with your doctor or pharmacist if any of the following side effects continue or become troublesome.

Possible side-effectsWhat can I do if I experience this
Nausea and vomitingIt usually passes after a few days as you adjust to the medicine. Your doctor may be able to prescribe a medicine to ease nausea.
DrowsinessMake sure your reactions are normal before driving, operating machinery or doing any other jobs which could be dangerous if you were not fully alert.
ConstipationTry to eat a well balanced diet containing fibre and drink 6-8 glasses of water each day. Your doctor may be able to prescribe a laxative.
Dry mouthIf you experience this, try chewing sugar-free gum, sucking sugar-free sweets or pieces of ice.
SweatingUse a cold/wet flannel or sponge placed on the forehead.
Difficulty urinating (passing water), flushing (redness of the face), a fast or fluttering heartbeat, seeing or hearing things that aren't real, mood changes, sexual problems or skin rashesIf this occurs speak with your doctor.

How to store pentazocine

  • Keep all medicines out of the reach of children.
  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines


  • Keep all medicines out of the sight and reach of children.
  • Make sure that the person prescribing this medicine knows about any other medicines that you are taking. This includes medicines you buy and herbal and homeopathic medicines.
  • If you buy any medicines check with a pharmacist that they are safe to take with your other medicines.
  • Before taking this medicine tell your doctor if you have ever had an allergic reaction after taking any medicine.
  • Never take more than the prescribed dose. If you suspect that you or someone else has taken an overdose of this medicine go to the accident and emergency department of your local hospital at once. Always take the container with you, if possible, even if it is empty.
  • If you are having any treatment like an operation or dental treatment tell the person carrying out the treatment which medicines you are taking.
  • Always read the printed information leaflet that comes with your medicine.
  • This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
  • Never keep out of date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.
  • If you have any questions about this medicine ask your pharmacist.
© EMIS 2007DocID:
3596		DocRef:
dils3117		Last Reviewed:
25 Jun 2007		Version:
22
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