Last Updated on April 17, 2025 by Analgesia team
Pain is universal.
From a pounding headache to chronic back pain that won’t go away, we’ve all reached for pain relief at some point. But with so many options lining pharmacy shelves — and even more behind the counter — how do you know which one is best for your situation?
So what’s the strongest painkiller?
Is it something you can grab over the counter, or do you need a prescription? And what about side effects?
We’ve got you covered.
In this guide, we’re breaking down the 10 most commonly used painkillers in the UK, ranked by their overall strength — from everyday options like paracetamol to heavy-duty prescription painkillers like morphine.
For each one, you’ll get a quick, practical overview:
- What it is used for
- How it works
- Strength level (1–10 scale)
- Effectiveness
- Side effects to watch for
- Whether it’s over the counter or prescription only
Bonus: We’ll also take a quick look at OxyContin — a powerful but highly controlled painkiller you’ve probably heard about for all the wrong reasons.
Ready to get clarity on which painkillers pack the most punch?
Let’s dive in.
Painkiller | Strength (1–10) | OTC / Prescription | Best For | Risk Level |
|---|---|---|---|---|
Paracetamol | 2 | OTC | Mild pain, fever, headaches | Low |
Ibuprofen | 3 | OTC | Inflammation, muscle pain, cramps | Low-Medium |
Co-codamol | 4 | OTC(low dose)/Rx | Moderate pain, dental pain | Medium |
Codeine | 5 | Prescription | Moderate pain, post-injury | Medium |
Tramadol | 7 | Prescription | Moderate to severe pain | Medium–High |
Morphine | 8 | Prescription | Severe pain, post-op, cancer | High |
Fentanyl | 9 | Prescription | Chronic or breakthrough cancer pain | High-Very High |
Buprenorphine | 9 | Prescription | Severe or chronic pain, opioid therapy | High |
Oxycodone | 10 | Prescription | Unmanageable or chronic pain | Very High |
Paracetamol (Panadol, Calpol)
Strength Level: 1/10
What it’s used for:
Paracetamol is the UK’s most commonly used painkiller — and for good reason. It’s your go-to option for everyday pain like headaches, mild muscle aches, period pain, or fever.
How it works:
It works by blocking chemical messengers in the brain that signal pain and fever. Unlike anti-inflammatory drugs (like ibuprofen), paracetamol doesn’t reduce swelling — it simply eases the sensation of pain.
Effectiveness:
For mild to moderate pain, it’s often the first-line recommendation. It’s not ideal for deep inflammatory conditions like arthritis, but great for general use and when NSAIDs can’t be taken (e.g., by people with stomach issues or asthma).
Side effects:
Paracetamol is considered very safe at normal doses. But — and this is a big one — overdosing can seriously damage the liver, and it’s a leading cause of liver failure in the UK.
Availability:
Over the counter (sold without prescription)
Available in tablets, capsules, syrup (for children), and even suppositories.
“Paracetamol is the gentle giant of painkillers — mild, reliable, and surprisingly effective for everyday aches”.
Next up: Ibuprofen — let’s see where this everyday favourite ranks in strength and effectiveness.
2. Ibuprofen (Nurofen, Brufen)
Strength Level: 2/10
What it’s used for:
Ibuprofen is a step up from paracetamol when it comes to inflammation-driven pain. It’s widely used for conditions like muscle sprains, menstrual cramps, toothaches, and even arthritis flare-ups.
How it works:
Ibuprofen is a non-steroidal anti-inflammatory drug (NSAID). It blocks the production of prostaglandins — chemicals in the body that cause pain, swelling, and inflammation.
Effectiveness:
Very effective for short-term relief where inflammation is involved. It works quickly and can last for 4–6 hours. However, it’s not ideal for long-term use, especially in people with stomach issues or high blood pressure
Side effects:
Ibuprofen can irritate the stomach lining and increase the risk of ulcers or gastrointestinal bleeding. Long-term use may affect kidney function or heart health — especially in older adults.
Availability:
Over the counter (200mg)
Higher doses (e.g., 400–800mg) require a prescription in the UK
“While ibuprofen is widely available over the counter, it sits relatively low on the painkiller strength scale — especially when compared to prescription options like tramadol or morphine.”
3. Aspirin (Disprin, Anadin Original)
Strength Level: 3/10
What it’s used for:
Aspirin has been around for over a century, and it still earns its spot on the shelf. It’s commonly used for mild to moderate pain — like headaches, toothaches, and period pain — but it’s also widely used in low doses to prevent heart attacks and strokes.
How it works:
Like ibuprofen, aspirin is a non-steroidal anti-inflammatory drug (NSAID). It works by reducing the production of prostaglandins — chemicals that cause inflammation, pain, and fever.
Effectiveness:
Aspirin is effective for short-term pain, particularly when inflammation is involved. However, it’s not often recommended as a first-line painkiller anymore due to its side effect profile and the rise of gentler alternatives.
Side effects:
Aspirin is harsher on the stomach than paracetamol or ibuprofen. It can lead to ulcers, bleeding, or digestive upset — and it’s not suitable for children under 16 due to the risk of Reye’s syndrome, a rare but serious condition.
Availability:
Over the counter
Sold in low-dose (75mg) tablets for heart health and standard-dose (300–600mg) for pain relief.
Aspirin is the old-school multitasker — part painkiller, part heart protector
4. Naproxen (Naproxen, Feminax Ultra)
Strength Level: 4/10
What it’s used for:
Naproxen is a go-to for longer-lasting pain relief, especially when inflammation is involved. It’s commonly used for arthritis, back pain, period cramps, and sports injuries — basically anything that sticks around and needs more than a quick fix.
How it works:
Naproxen is an NSAID, just like ibuprofen and aspirin, but it lasts longer in the body. It reduces inflammation and pain by inhibiting the same prostaglandins, but with a longer half-life.
Effectiveness:
Because it sticks around longer, naproxen is often prescribed for chronic or recurring pain. One dose can relieve symptoms for up to 12 hours, making it ideal for day-to-day management of things like joint pain or heavy periods.
Side effects:
It shares the same concerns as other NSAIDs — stomach irritation, heartburn, and increased risk of ulcers or bleeding. It may also affect kidney function if used long-term, especially in older adults.
Availability:
Low doses (250mg) are available over the counter for period pain and general aches.
Higher doses require a prescription, especially for chronic conditions like arthritis.
Naproxen is the slow burner — not the fastest painkiller, but one that goes the distance
Next in line: #5. Codeine — our first proper entry into the opioid territory.
5. Codeine (Co-codamol, Solpadeine)
Strength Level: 5/10
What it’s used for:
Codeine is used for moderate pain that doesn’t respond well to standard OTC options. It’s often combined with paracetamol (as in co-codamol) or ibuprofen for added effect. Think post-surgery recovery, dental pain, or pain from injuries.
How it works:
Codeine is an opioid, meaning it works by binding to opioid receptors in the brain and spinal cord to block pain signals. Once ingested, a portion of it converts into morphine inside the body — that’s where the pain-relieving magic comes from.
Effectiveness:
It can be effective for pain that’s more persistent or intense, but reactions vary. Some people don’t metabolise it well, making it less effective for them. It’s typically used short-term due to risks of dependence and tolerance.
Side effects:
Codeine can cause drowsiness, constipation, nausea, and dizziness. There’s also a risk of developing dependency, even at therapeutic doses, if used over a long period
Availability:
Lower-dose codeine (e.g., 8mg) is available in combo meds like co-codamol — behind the counter at pharmacies.
Higher doses (15mg–30mg+) are prescription-only.
Codeine is where pain relief gets serious — but it walks a fine line between help and habit.
Next up: #6. Dihydrocodeine — a sibling of codeine that hits a little harder. Ready for it?
6. Dihydrocodeine (DF118, Co-dydramol)
Strength Level: 6/10
What it’s used for:
Dihydrocodeine is prescribed for moderate to moderately severe pain, especially when regular codeine doesn’t quite cut it. It’s used for things like post-operative pain, nerve pain, and musculoskeletal injuries. You’ll often find it combined with paracetamol in co-dydramol/Paramol
How it works:
It’s a semi-synthetic opioid, very similar to codeine, but slightly stronger. It targets the same opioid receptors in the brain and central nervous system, dulling pain perception and sometimes inducing a mild sedative effect.
Effectiveness:
It can provide solid pain relief, especially for those who don’t respond well to weaker opioids. Its effectiveness increases when combined with paracetamol or NSAIDs, making it a useful tool for short-term pain management.
Side effects:
Expect the usual opioid suspects — drowsiness, nausea, constipation, and potential dependence. Long-term use can lead to tolerance and withdrawal symptoms if stopped suddenly.
Availability:
Prescription-only in the UK
Available in tablets (often combined with paracetamol) and in slow-release forms for chronic pain.
Dihydrocodeine is the quiet cousin of codeine — stronger, steadier, and not to be underestimated
Next stop: #7. Tramadol — a synthetic opioid that lives in the grey zone between common painkillers and heavy hitters.
7. Tramadol (Zamadol, Tramal)
Strength Level: 7/10
What it’s used for:
Tramadol is prescribed for moderate to severe pain, especially when other opioids like codeine or dihydrocodeine aren’t effective enough. It’s used post-surgery, for injury recovery, or in managing chronic conditions like fibromyalgia.
How it works:
Tramadol is a synthetic opioid, but with a twist — it doesn’t just act on opioid receptors. It also affects serotonin and norepinephrine levels, which can amplify its painkilling effect. This gives it a dual mechanism that sets it apart.
Effectiveness:
It tends to be more powerful than codeine-based meds but not quite as intense as morphine. It’s often well-tolerated in the short term and can be a good middle ground for those needing something stronger than basic opioids.
Side effects:
Because of its action on brain chemicals, tramadol can cause dizziness, confusion, mood changes, and even seizures in some people. There’s also a known risk of addiction, especially with long-term use.
Availability:
Prescription-only in the UK
Available in tablets, capsules, drops, and extended-release forms.
Tramadol is the wildcard — half opioid, half antidepressant, and fully effective when handled with care.
Next up: #8. Morphine — the gold standard for severe pain.
8. Morphine (Oramorph, Sevredol)
Strength Level: 8/10
What it’s used for:
Morphine is the go-to for severe pain — post-operative, cancer-related, or pain caused by major trauma. It’s widely used in hospitals and palliative care settings when pain can’t be managed by weaker opioids.
How it works:
It’s a powerful opioid analgesic that binds strongly to opioid receptors in the brain and spinal cord. This blocks pain signals and produces a sense of calm — sometimes even euphoria — depending on the dose
Effectiveness:
Morphine sets the standard by which other opioids are measured. It’s highly effective for intense pain and comes in various forms to suit short-term or long-term needs, including oral liquids, tablets, and injections.
Side effects:
Strong opioids come with strong warnings. Morphine can cause severe drowsiness, constipation, nausea, and respiratory depression at higher doses. Dependence and tolerance are common with prolonged use.
Availability:
Prescription-only
Available in short-acting and modified-release forms for sustained pain relief.
Morphine is the heavyweight champ — powerful, reliable, and not to be messed with.
Up next: #9. Fentanyl — one of the strongest painkillers on the planet, and a major player in both medicine and the headlines.
9. Fentanyl (Durogesic, Actiq)
Strength Level: 9/10
What it’s used for:
Fentanyl is reserved for severe, unrelenting pain — especially in cancer patients or individuals who have already built tolerance to other opioids like morphine. It’s not a first-line drug; it’s used when others stop working.
How it works:
Fentanyl is a synthetic opioid that binds intensely to opioid receptors. It’s about 50–100 times stronger than morphine, meaning even tiny doses can have massive effects. It’s often administered through skin patches, lozenges, or injections for long-lasting relief.
Effectiveness:
Extremely potent. It kicks in fast and lasts long, especially in patch form. It’s designed for patients already on a steady opioid routine, not beginners.
Side effects:
Fentanyl carries high risks — including drowsiness, nausea, severe respiratory depression, and fatal overdose if misused. It’s also linked to the ongoing opioid crisis, particularly in the illicit drug market.
Availability:
Prescription-only and strictly controlled
Available as patches, lozenges (“lollipops”), nasal sprays, or injections.
Fentanyl is the nuclear option — powerful relief for pain that won’t back down.
10. Buprenorphine (Butec, Transtec, Subutex)
Strength Level: 9/10
What it’s used for:
Buprenorphine is a high-strength opioid used for both moderate to severe pain and opioid addiction treatment. It’s unique because it relieves pain while also helping people come off other opioids — making it a bit of a double agent.
How it works:
t’s long-acting and potent, especially in patch or sublingual tablet form. It’s often used when round-the-clock pain relief is needed or when other opioids have caused problems. Also used in detox and maintenance therapy under the brand Subutex or Suboxone.
Side effects:
Common effects include nausea, dizziness, headache, constipation, and sedation. Because of the ceiling effect, it’s considered safer than full opioids in overdose situations — but it’s still addictive if misused.
Availability:
Prescription-only
Comes in patches, tablets, injections, and films.
Buprenorphine is the strategist — strong enough for pain, smart enough to limit harm.
You ready for the Bonus Round? Let’s give a spotlight to OxyContin (Oxycodone) — one of the most talked-about opioids in recent history.
Bonus: Oxycodone (OxyContin, Oxynorm)
Strength Level: 10/10
What it’s used for:
Oxycodone is prescribed for severe, chronic, or post-surgical pain — especially in cases where morphine isn’t tolerated or isn’t strong enough. It’s used in cancer care, major injuries, and end-of-life pain management.
How it works:
Oxycodone is a full opioid agonist, binding strongly to receptors in the brain and spinal cord to block pain signals. It’s highly bioavailable, meaning it kicks in quickly and effectively — but this also makes it highly addictive.
Effectiveness:
Extremely potent. Available in immediate-release (Oxynorm) for quick relief or extended-release (OxyContin) for 12-hour coverage. It’s regarded as one of the strongest prescription painkillers available outside of hospital-only drugs.
Side effects:
The side effects match its strength — drowsiness, nausea, constipation, confusion, and high risk of respiratory depression. It also carries a serious addiction and abuse risk, making it a central figure in the opioid crisis, especially in the U.S.
Availability:
Prescription-only in the UK
Available in tablets, capsules, liquid, and injection.
Oxycodone is the kingpin — a last-resort lifeline for pain or a slippery slope, depending on how it’s used.
Final Thoughts
Pain comes in many forms — and so do the medications we use to treat it. From everyday headaches to post-surgical recovery, the UK has a wide range of painkillers tailored to different needs and strengths. But while access is easier than ever, knowing which option is right for your situation is crucial.
Always consult with your GP or pharmacist before starting or changing any medication, especially when it comes to stronger, prescription-based painkillers. What works for one person may not work — or be safe — for another.
And remember:
Stronger doesn’t always mean better. Sometimes, the most effective painkiller is the one that causes the fewest problems.