Palexia SR (Tapentadol)

How does it work?

Palexia SR tablets contain the active ingredient tapentadol, which is a type of medicine called an opioid painkiller. The opioids are a group of very strong painkillers related to morphine.

Opioid painkillers work by mimicking the action of naturally occurring pain-reducing chemicals called endorphins. Endorphins are found in the brain and spinal cord and reduce pain by combining with opioid receptors.

Tapentadol mimics the action of natural endorphins by combining with the opioid receptors in the brain and spinal cord. This blocks the transmission of pain signals sent by the nerves to the brain. Therefore, even though the cause of the pain may remain, less pain is actually felt.

Tapentadol also has another action on the nerve cells in the brain. In the brain there are numerous different chemical compounds called neurotransmitters. These act as chemical messengers between the nerve cells. Noradrenaline is one such neurotransmitter and has various functions that we know of.

Tapentadol prevents noradrenaline from being reabsorbed back into the nerve cells in the brain and thus enhances its activity in the brain. Medicines that increase the activity of noradrenaline in the brain have been shown to be effective at relieving nerve pain and also to enhance the effect of opioid painkillers.

Tapentadol is used to relieve moderate to severe pain that is not relieved by weaker painkillers.

Palexia SR tablets are a 'long-acting' or 'prolonged-release' form of tapentadol. The tablets are designed to release the medicine slowly over 12 hours to provide a steady blood level of the medicine throughout the day and thus provide continuous pain relief from chronic severe pain.

What is it used for?

  • Severe long-standing pain in adults that can only be relieved with opioid painkillers, for example pain associated with osteoarthritis or chronic low back pain.

How do I take it?

  • Palexia SR tablets are usually taken twice a day (every 12 hours). The dose prescribed by your doctor will depend on how severe your pain is, whether you have previously been taking other opioid painkillers and various other factors. Do not take more than the prescribed dose.
  • The tablets should be swallowed whole with a drink of water. They must not be broken, crushed or chewed, as this would damage the prolonged-release action and could lead to an overdose of the medicine.
  • The tablets can be taken either with or without food.


  • This medicine may cause drowsiness, dizziness, blurred vision, slow reaction times and confusion and so could affect your ability to drive and operate machinery safely. If you are affected do not drive or operate machinery.
  • You should avoid drinking alcohol while taking this medicine as it is likely to increase any drowsiness or dizziness that you experience.
  • If this medicine is taken for prolonged periods of time the body may become dependent on the medicine and, as a result, you may get withdrawal symptoms if it is stopped suddenly. For this reason, when you no longer need this medicine it may be necessary to reduce it gradually to avoid withdrawal symptoms. Follow the instructions given by your doctor.

Use with caution in

  • Elderly people.
  • Weak or debilitated people.
  • People with moderately decreased liver function.
  • People with decreased lung function or breathing difficulties, for example asthma (see also below).
  • People with a head injury or brain tumour.
  • People with epilepsy or who are prone to fits.
  • Diseases of the bile ducts, eg gallstones.
  • Inflammation of the pancreas (pancreatitis).
  • People with a history of drug, alcohol or medication dependence or abuse.

Not to be used in

  • People with very slow, shallow breathing (respiratory depression).
  • People with severe asthma or who are having an acute asthma attack.
  • People with inactivity in the intestines that is causing an obstruction in the gut (paralytic ileus).
  • People who are intoxicated with alcohol, sleeping pills, painkillers or medicines or drugs that affect mood and emotions.
  • People with raised pressure inside the skull (raised intracranial pressure).
  • People with reduced levels of consciousness or who are in a coma.
  • People who have taken a monoamine-oxidase inhibitor antidepressant (MAOI) in the last 14 days.
  • People with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption (Palexia SR tablets contain lactose).
  • Breastfeeding.
  • This medicine is not recommended for people with severely decreased kidney or liver function.
  • This medicine is not recommended for children and adolescents under 18 years of age.

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.

Pregnancy and 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 for use during pregnancy has not been established. It should not be used during pregnancy unless considered essential by your doctor. It is not recommended for use during labour or delivery because it may cause breathing difficulties in the baby after birth. Seek further medical advice from your doctor.
  • It is not known if this medicine passes into breast milk. It should not be used by women who are breastfeeding. Seek further medical advice from your doctor.

Side effects

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, it does not mean that all people using this medicine will experience that or any side effect.

Very common (affect more than 1 in 10 people)

  • Sleepiness.
  • Dizziness.
  • Headache.
  • Nausea.
  • Constipation.

Common (affect between 1 in 10 and 1 in 100 people)

  • Decreased appetite.
  • Anxiety, nervousness or restlessness.
  • Depressed mood.
  • Problems with attention.
  • Tremor.
  • Muscle spasms.
  • Flushing.
  • Feeling short of breath.
  • Disturbances of the gut such as vomiting, diarrhoea, indigestion.
  • Rash.
  • Itching.
  • Sweating.
  • Feeling weak or tired.
  • Dry mouth.
  • Fluid retention (oedema).

Uncommon (affect 1 in 100 and 1 in 1000 people)

  • Weight loss.
  • Feeling agitated, confused or disorientated.
  • Euphoric mood.
  • Abnormal dreams.
  • Problems with thinking or memory.
  • Sedation.
  • Problems with speech.
  • Problems with balance.
  • Pins and needles or numb sensations.
  • Fainting.
  • Visual disturbances.
  • Increased or decreased heart rate.
  • Decreased blood pressure.
  • Abnormally frequent urination, but also a delay in starting to urinate when you go.
  • Sexual problems.
  • Feeling abnormal or irritable.

Rare (affect between 1 in 1000 and 1 in 10,000 people)

  • Very slow, shallow breathing (respiratory depression).
  • Feeling drunk or relaxed.
  • Dependence on the medicine (see warning section above).
  • Convulsions.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect 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 ensure that the combination is safe.

This medicine should not be taken by people who are taking a monoamine oxidase inhibitor antidepressant (MAOI), for example the antidepressants phenelzine, tranylcypromine or isocarboxazid, or by people who have taken one of these medicines in the last 14 days.

There may be an increased risk of drowsiness, sedation and breathing difficulties if this medicine is taken with any of the following:

  • alcohol
  • antipsychotic medicines, eg chlorpromazine, haloperidol
  • antisickness medicines, eg nabilone
  • barbiturates, eg phenobarbital, amobarbital
  • benzodiazepines, eg diazepam, temazepam
  • other strong opioid painkillers, eg morphine, codeine
  • sedating antihistamines, eg chlorphenamine, hydroxyzine, promethazine
  • sleeping tablets, eg zopiclone
  • tricyclic and related antidepressants eg amitriptyline, mirtazapine.

There may be an increased risk of a rare side effect called the serotonin syndrome if tapentadol is taken in combination with other medicines that enhance the activity of serotonin in the central nervous system, such as the following:

  • selective serotonin reuptake inhibitor antidepressants (SSRIs), such as citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine or sertraline
  • serotonin noradrenaline reuptake inhibitors (SNRIs), such as venlafaxine or duloxetine
  • triptans for migraine, such as sumatriptan, zolmitriptan.

If you are taking any of these medicines you should let your doctor know if you experience symptoms such as confusion, agitation, tremor, muscle twitching, shivering, sweating, racing heartbeat or diarrhoea after taking tapentadol.

The following medicines may increase the breakdown of tapentadol in the body:

  • phenobarbital
  • rifampicin
  • the herbal remedy St John's wort (Hypericum perforatum).

If one of these medicines is started while taking Palexia SR it may make it less effective. If treatment with one of these medicines is stopped while taking Palexia SR this may result in increased levels of tapentadol in the blood, which could increase the risk of side effects.

Other medicines containing the same active ingredient