Tapentadol side effects: common, serious and long-term

The most common tapentadol side effects are feeling sick, constipation, dizziness, drowsiness and headache, each affecting more than 1 in 10 people. Rarer but serious effects include slow or shallow breathing, fits, serotonin syndrome and dependence. Call 999 if someone taking tapentadol is very hard to wake or their breathing becomes slow, shallow or stops.

This guide explains every side effect listed in the official UK leaflets for tapentadol, how often each one happens and what to do about it. It also covers the warning signs that need urgent help, long-term effects and what an overdose looks like. For an overview of the medicine itself, read our complete guide to tapentadol.

How common are tapentadol side effects?

The patient leaflet for Palexia SR prolonged-release tablets (revised November 2025) groups side effects by how often they were reported. The table below summarises it in plain words.

How often	Side effects listed in the leaflet
Very common (more than 1 in 10 people)	Feeling sick, constipation, dizziness, drowsiness, headache
Common (up to 1 in 10)	Reduced appetite, anxiety, low mood, sleep problems, nervousness, restlessness, poor concentration, shaking, muscle twitches, flushing, shortness of breath, being sick, diarrhoea, indigestion, itching, sweating, rash, weakness, tiredness, feeling hot or cold, dry mouth, swelling from fluid
Uncommon (up to 1 in 100)	Severe allergic reactions, weight loss, confusion, disorientation, agitation, changes in perception, abnormal dreams, feeling overly happy, reduced alertness, memory problems, fainting, sedation, poor balance, difficulty speaking, numbness or tingling, vision changes, a faster or slower heartbeat, palpitations, low blood pressure, stomach discomfort, hives, problems passing urine, sexual problems, withdrawal symptoms, irritability
Rare (up to 1 in 1,000)	Drug dependence, abnormal thinking, fits, feeling faint, poor coordination, dangerously slow or shallow breathing, slowed stomach emptying, feeling drunk or relaxed
Not known	Delirium

The leaflet for immediate-release Palexia 50 mg tablets lists drug dependence as uncommon (up to 1 in 100) rather than rare. This follows a 2025 European safety review, described below. The Summary of Product Characteristics (SmPC) notes that delirium was reported mainly in people with cancer or of advanced age.

Common side effects and how to cope

Feeling sick and being sick

Nausea is very common, especially in the first days of treatment. Tell your prescriber or pharmacist if it does not settle or stops you eating and drinking.

Constipation

Constipation is one of the most typical opioid side effects. Drinking enough fluid, eating fibre and staying active may help. Ask your pharmacist or GP before using a laxative, and tell them if you have stomach pain or have not opened your bowels for several days.

Dizziness, drowsiness and headache

These are more likely when you start tapentadol or your dose changes. Get up slowly from sitting or lying down. Do not drive, cycle or use machinery until you know how the medicine affects you.

Low mood, anxiety and sleep problems

The leaflet lists anxiety, low mood and sleep problems as common. Speak to your GP if your mood changes, or if you have thoughts of harming yourself.

Serious side effects: warning signs to act on

Slow or shallow breathing

The leaflet says slowed or weakened breathing is most likely in older or frail people. The SmPC explains that the risk rises with higher doses. Call 999 if breathing becomes very slow, shallow or noisy, or the person cannot be woken.

Allergic reactions

Contact a doctor straight away if you notice wheezing, difficulty breathing, swelling of the eyelids, face or lips, or a widespread itchy rash. Call 999 if breathing is affected.

Fits (seizures)

In January 2019 the MHRA strengthened its warnings about seizures with tapentadol. It reported that about half of the spontaneous seizure reports involved at least one other medicine that lowers the seizure threshold. These include some antidepressants (SSRIs, SNRIs and tricyclics) and antipsychotics. Tell your prescriber if you have epilepsy or have ever had a fit.

Serotonin syndrome

Serotonin syndrome is rare but can be life-threatening. It has been reported when tapentadol is taken with serotonin-boosting antidepressants. The leaflet lists these warning signs:

• involuntary, rhythmic muscle jerks, including the eye muscles
• agitation and heavy sweating
• shaking and overactive reflexes
• stiff muscles
• a body temperature above 38°C

Seek urgent medical help if you notice these signs. Always tell your prescriber about every medicine you take, including antidepressants.

Breathing problems during sleep

Opioids can cause sleep apnoea, where breathing pauses during sleep. Signs include waking up short of breath, difficulty staying asleep and heavy drowsiness in the day. Tell your doctor if you or someone else notices these, as the leaflet says a lower dose may be considered.

Tapentadol 100 mg side effects and higher doses

The UK leaflets list the same possible side effects for every strength, including 100 mg tablets. What changes with strength is the level of risk for some effects. The SmPC states that breathing problems are dose-related and that the risk of sleep apnoea rises with the opioid dose.

The SmPC also says the risk of dependence and opioid use disorder increases with higher doses and longer treatment. Take tapentadol exactly as your prescriber tells you, and never take extra tablets for breakthrough pain unless they have told you to.

Long-term side effects of tapentadol

Tolerance and dependence

Repeated use can lead to tolerance, where the same dose works less well. It can also lead to physical dependence and addiction. In 2020 the MHRA warned that opioids can cause dependence and addiction, even at therapeutic doses. It also advised that you and your prescriber agree a plan for how long treatment will last and how it will end.

The leaflet lists signs of dependence to look out for. These include needing the medicine for longer than advised, taking more than prescribed, or using it to stay calm or to sleep. Speak to your doctor if you notice any of these.

Increased sensitivity to pain

The same MHRA advice says long-term opioid use can sometimes make you more sensitive to pain (hyperalgesia). This pain may feel different from your original condition. The MHRA says it may ease when the dose is gradually reduced under medical supervision.

Stronger warnings since 2025

A European periodic safety review adopted in July 2025 added clearer wording on dependence and its risk factors. These include a personal or family history of substance use disorders, current tobacco use and other mental health conditions. It also added advice to store the medicine somewhere secure.

What the long-term evidence shows

A 2019 review in the Journal of Pain Research found safety data for tapentadol covering up to 4 years. In a pooled analysis of four trials, stomach and bowel side effects were reported by 47.3% of people on prolonged-release tapentadol and 26.6% on placebo. The review was funded by the manufacturer, so read its conclusions with that in mind.

Withdrawal symptoms

Stopping suddenly can cause withdrawal, especially after long-term use. Our guide to tapentadol withdrawal symptoms explains how to stop safely with your prescriber. The leaflet lists restlessness, watery eyes, a runny nose, yawning, sweating, chills, aches, stomach cramps, poor sleep, feeling sick and diarrhoea. Do not stop taking tapentadol without speaking to your prescriber. They can plan a gradual reduction that suits you.

Tapentadol overdose: signs and what to do

Taking too much tapentadol is a medical emergency. The leaflet lists these signs of a very high dose:

• pinpoint pupils
• being sick
• low blood pressure and a fast heartbeat
• collapse, confusion or not being able to stay awake
• fits
• slow, shallow or stopped breathing, which can be fatal

Call 999 straight away if you see these signs. Stay with the person and tell the call handler what they have taken. The SmPC explains that hospital teams can give naloxone to reverse breathing problems. Because naloxone can wear off before the opioid does, the person still needs to be watched in hospital.

The SmPC warns that taking tapentadol with alcohol, benzodiazepines or other sedatives can cause deep sedation, slowed breathing, coma and death. Gabapentin and pregabalin also raise the risk of overdose. If you think you have taken more than prescribed, the leaflet says to contact a doctor immediately. Call NHS 111 if you cannot reach your GP.

Alcohol, other medicines and driving

• Alcohol: the leaflet says do not drink alcohol while taking tapentadol, as it increases drowsiness and other side effects.
• Sleeping tablets and sedatives: these add to drowsiness and slowed breathing. If you also take a sleeping tablet, our guide to zopiclone side effects covers next-day drowsiness and why your prescriber needs to know about your other medicines.
• MAOI antidepressants: tapentadol should not be used if you have taken an MAOI in the last 14 days, because of the risk of a dangerous rise in blood pressure.
• Driving: the leaflet says not to drive until you know how tapentadol affects you. Under drug-driving law in England, Scotland and Wales, it is illegal to drive if a legal medicine impairs your driving. Penalties include a minimum one-year driving ban, an unlimited fine and up to 6 months in prison.

Legal status and safe storage

Tapentadol was added to Class A of the Misuse of Drugs Act by the Misuse of Drugs Act 1971 (Amendment) Order 2011. It is also a Schedule 2 controlled drug, so it is only available on prescription with extra prescribing and storage rules. Our guide to controlled drugs in the UK explains what this means for you.

The leaflet asks you to keep tapentadol in a safe, secure place where other people cannot reach it. It can cause serious harm or death if taken by someone it was not prescribed for. Only get tapentadol from a registered pharmacy with a valid prescription. You can check whether an online pharmacy is legitimate before you use it.

This article is for information only and does not replace advice from your doctor or pharmacist. Read our medical disclaimer.