Painkillers compared: ibuprofen, paracetamol, diclofenac and ASA

With headaches, toothache, fever or joint complaints, most people reach for over-the-counter painkillers from the pharmacy. But which is the right one? Ibuprofen, paracetamol, diclofenac and acetylsalicylic acid (ASA, e.g. aspirin) are the four most commonly used — and they differ clearly in their effect, areas of use and risks.

What this is about A comparison of the four most important over-the-counter painkillers: ibuprofen, paracetamol, diclofenac, ASA. The two groups: NSAIDs (ibuprofen, diclofenac, ASA) — anti-inflammatory; paracetamol — pain-relieving/fever-reducing, barely anti-inflammatory. Most important differences: mechanism of action, anti-inflammatory effect, risk profile (stomach, kidney, heart, liver). Basic rule: the lowest effective dose, for as short a time as possible; with pre-existing conditions and continuous use, consult a doctor. Important: over-the-counter does not mean harmless.

1. The two big groups: NSAIDs and paracetamol

To understand the four painkillers, it helps to divide them fundamentally into two groups with a different working principle:

NSAIDs (non-steroidal anti-inflammatory drugs)

This group includes ibuprofen, diclofenac and ASA. They inhibit the enzyme cyclooxygenase (COX) and thus the formation of prostaglandins — messenger substances involved in pain, inflammation and fever. NSAIDs therefore act in three ways: pain-relieving, anti-inflammatory and fever-reducing. Their anti-inflammatory effect makes them especially good for inflammatory and tissue pain — but also brings the typical risks (stomach, kidney, heart), because prostaglandins also have protective functions in the body.

Paracetamol — a special case

Paracetamol does not belong to the NSAIDs. Its mechanism of action is still not fully understood; it mainly acts centrally in the brain as a pain reliever and fever reducer, but has barely any anti-inflammatory effect. The big advantage: it burdens the stomach and kidney considerably less than NSAIDs. The most important danger, by contrast, lies with overdose in the liver.

This fundamental distinction — NSAIDs with an anti-inflammatory effect and corresponding risks, paracetamol without notable anti-inflammatory effect and with a different risk profile — is the key to the right choice.

2. Ibuprofen at a glance

Ibuprofen is one of the most widely used painkillers of all — a well-tolerated NSAID with a balanced profile.

  • Effect: pain-relieving, anti-inflammatory, fever-reducing
  • Strengths: very broadly usable — headache, toothache, period, muscle and joint pain, fever; good anti-inflammatory effect
  • Duration of effect: medium-length (several hours)
  • Main risks: gastrointestinal complaints (gastric lining), strain on the kidneys, with higher doses/continuous use a cardiovascular risk
  • Particularity: over-the-counter in low doses, higher doses prescription-only
  • Good to know: better tolerated by the stomach with or after food

Ibuprofen is often a good first choice for pain with an inflammatory component (e.g. toothache, period pain, joint pain). Like all NSAIDs, it should be used at the lowest effective dose and for as short a time as possible.

3. Paracetamol at a glance

Paracetamol is the painkiller with the gentlest profile for stomach and kidney — for which the liver is the critical point.

  • Effect: pain-relieving and fever-reducing, barely anti-inflammatory
  • Strengths: gentle on stomach and kidney; good for headaches, fever, mild to moderate pain; often the agent of choice in pregnancy (after consulting a doctor) and with stomach problems
  • Main risk: liver damage with overdose — the safety margin is smaller than many think
  • Important: strictly keep to the maximum daily dose; caution with liver diseases and regular alcohol consumption
  • Good to know: contained in many combination/cold preparations — risk of unintentional double dosing
Paracetamol overdose: danger to the liver Paracetamol is very safe at the correct dose — but an overdose can lead to severe, sometimes irreversible liver damage. Never take more than the stated maximum daily dose, and watch out that paracetamol is not taken twice at the same time across several preparations (e.g. cold remedies). With an accidental overdose, seek medical help immediately — even if you feel well at first.

4. Diclofenac at a glance

Diclofenac is a strong NSAID with a particularly pronounced anti-inflammatory effect — often used for joint and muscle complaints.

  • Effect: strongly pain-relieving and anti-inflammatory, fever-reducing
  • Strengths: very good for inflammatory joint, muscle and back pain, osteoarthritis, sports injuries
  • Form: as a tablet, but also as a gel/ointment to apply (local, considerably lower systemic burden)
  • Main risks: as with NSAIDs, gastrointestinal and kidney risk; with systemic use (tablets) a somewhat higher cardiovascular risk than ibuprofen
  • Good to know: the gel is a stomach-friendly option for local complaints (e.g. bruise, strain)

Diclofenac as a tablet is usually prescription-only or pharmacy-only in low doses; the gel is over-the-counter. Especially for local complaints, the external use as a gel is a sensible, gentler alternative to the tablet.

5. ASA (acetylsalicylic acid) at a glance

ASA (known as aspirin) is a classic with a special feature: it has two very different areas of use depending on the dose.

  • Effect: pain-relieving, anti-inflammatory, fever-reducing (in higher doses) — AND blood-thinning (in low doses)
  • As a painkiller (higher dose): good for headache and aching limbs, fever
  • As a blood thinner (low dose, e.g. 100 mg): for the prevention of heart attack and stroke in at-risk patients — a completely different use
  • Main risks: a pronounced gastrointestinal bleeding risk, inhibits blood clotting (for longer than other NSAIDs)
  • Important warning: NOT for children and adolescents with feverish (especially viral) infections — risk of the rare but dangerous Reye's syndrome
ASA in children: Reye's syndrome risk ASA should not be used to treat fever/pain in children and adolescents with feverish infections (Reye's syndrome risk). In addition, ASA inhibits blood clotting for longer than other painkillers — relevant before operations and with a tendency to bleed. Low-dose ASA for the prevention of heart attack/stroke is a separate medical therapy and not to be confused with its use as a painkiller.

6. The direct comparison

The four painkillers at a glance — their most important properties compared:

  • Anti-inflammatory effect: diclofenac (strong) > ibuprofen/ASA (good) > paracetamol (barely)
  • Stomach tolerability: paracetamol (best) > ibuprofen > diclofenac > ASA (most critical)
  • Kidney burden: paracetamol (low) < the NSAIDs (relevant, especially with continuous use/pre-existing condition)
  • Liver risk: above all paracetamol (with overdose) — with the NSAIDs less often in the foreground
  • Cardiovascular: diclofenac (with continuous use tends to be the highest risk) > ibuprofen; paracetamol the most neutral
  • Blood clotting: ASA inhibits it strongly and for a long time; other NSAIDs temporarily; paracetamol barely
  • In pregnancy: paracetamol often the agent of choice (after consulting a doctor); avoid NSAIDs especially in the last trimester

In short: paracetamol is the gentlest agent for stomach, kidney and heart, but has barely any anti-inflammatory effect and a liver risk with overdose. The NSAIDs (ibuprofen, diclofenac, ASA) additionally have an anti-inflammatory effect, but burden the stomach, kidney and cardiovascular system more. Which one fits depends on the type of complaint and individual risk factors.

7. Which painkiller for which complaints?

A practical orientation — but the final choice always depends on individual factors (pre-existing conditions, other medications):

  • Headache: ibuprofen, paracetamol or ASA; with tension headache often ibuprofen/paracetamol
  • Toothache: ibuprofen (good anti-inflammatory effect)
  • Period pain: ibuprofen (works well against the inflammatory-cramping component)
  • Joint/muscle pain, osteoarthritis, back: ibuprofen or diclofenac (anti-inflammatory); locally diclofenac gel
  • Fever: paracetamol or ibuprofen; in children prefer these two (no ASA)
  • With a sensitive stomach: prefer paracetamol
  • In pregnancy: paracetamol (after consulting a doctor); avoid NSAIDs, especially in the last trimester
  • In children: paracetamol or ibuprofen in an age-appropriate form; NO ASA

For inflammatory and tissue pain, the NSAIDs are often superior; for simple pain and fever without inflammation, paracetamol is a gentle choice. With persistent or severe pain, the choice belongs in a doctor's hands.

8. The risks compared: stomach, kidney, heart, liver

Over-the-counter painkillers also have relevant risks — above all with higher doses, long use and pre-existing conditions. The most important organs in focus:

Gastrointestinal tract (above all NSAIDs)

NSAIDs (ibuprofen, diclofenac, ASA) can damage the gastric lining — from stomach pain to ulcers and bleeding. The risk rises with continuous use, older age, previous ulcers and combination with other agents (cortisone, blood thinners). ASA is the most critical here. Paracetamol is gentle on the stomach.

Kidneys (above all NSAIDs)

NSAIDs can impair blood flow to the kidneys — risky with pre-existing kidney disease, fluid deficiency, older age and combination with certain blood-pressure agents (the "triple whammy" of NSAID + ACE inhibitor/ARB + diuretic).

Cardiovascular (NSAIDs)

With longer use and higher doses, NSAIDs can slightly raise the risk of heart attack and stroke and increase blood pressure — diclofenac tends to do so more than ibuprofen. With pre-existing cardiovascular conditions, consult a doctor.

Liver (above all paracetamol)

Paracetamol can severely damage the liver with overdose. At the correct dose it is very safe — what is critical is overdose, pre-existing liver disease and regular alcohol consumption.

9. Can you combine painkillers?

A common question — the answer depends on the combination:

  • Paracetamol + NSAID (e.g. ibuprofen): can be sensible in certain situations, since the mechanisms of action differ — but only on the recommendation of a doctor/pharmacist and for a limited time
  • Two NSAIDs together (e.g. ibuprofen + diclofenac or + ASA): NOT advisable — no additional benefit, but added risk (stomach, kidney)
  • ASA (as a blood thinner) + NSAID: problematic — ibuprofen can weaken the heart-protecting effect of low-dose ASA; a doctor's consultation is needed
  • Caution with combination preparations: many cold/pain remedies already contain paracetamol or ASA — risk of unnoticed double dosing

Basic rule: different NSAIDs are not combined. The combination of paracetamol + NSAID is the only common sensible combination, but it too should be discussed and time-limited. Always check whether an active ingredient is already contained in another preparation.

10. Painkillers and interactions

Over-the-counter painkillers can also interact with other medications. Important examples:

  • NSAIDs + blood thinners (Marcumar, apixaban, ASA): increased bleeding risk
  • NSAIDs + blood-pressure agents (ACE inhibitors, valsartan, diuretics): weakened blood-pressure lowering, kidney burden
  • NSAIDs + cortisone: strongly increased gastrointestinal risk
  • NSAIDs + certain antidepressants (SSRIs): increased bleeding risk
  • Paracetamol + certain medications/alcohol: increased liver burden
  • ASA + other blood-thinning agents: added bleeding risk

Anyone who regularly takes medications or has pre-existing conditions should ask a doctor or the pharmacy before taking over-the-counter painkillers. More under drug interactions and taking medications correctly.

11. Painkillers and alcohol

Combining painkillers and alcohol is generally unfavourable — with different emphases:

  • Paracetamol + alcohol: increased liver risk — both are metabolized in the liver; especially problematic with regular/higher alcohol consumption
  • NSAIDs + alcohol: increased gastrointestinal bleeding risk (both irritate the gastric lining)
  • In general: alcohol can make it harder to judge pain and side effects

Practical recommendation: if possible, do not take painkillers and alcohol together — above all do not combine paracetamol with regular alcohol consumption (liver), and do not take NSAIDs with alcohol if you have a sensitive stomach.

12. When over-the-counter painkillers are not enough

Over-the-counter painkillers are intended for temporary, mild to moderate pain. In certain situations they are not enough or even dangerous, because they mask serious causes:

  • Pain lasting longer than a few days without improvement — have it medically clarified
  • Very severe or suddenly starting pain — can have serious causes
  • Regular painkiller use (e.g. more than 10 days a month for headaches) — risk of headaches from painkillers (medication-overuse headache)
  • Accompanying symptoms such as fever, neurological deficits, chest pain, severe abdominal pain — clarify medically/as an emergency
  • Chronic pain — belongs in a medical pain-management plan (possibly with prescription agents such as tilidine or nerve-pain agents such as gabapentin)

Important: pain is a warning signal. Anyone who regularly or permanently needs painkillers should have the cause medically clarified, instead of just suppressing the symptoms.

13. The most important safety rules

Ten golden rules that apply to all over-the-counter painkillers:

  • Use the lowest effective dose, for as short a time as possible.
  • Strictly keep to the maximum daily dose — above all with paracetamol.
  • Avoid double dosing — check whether the active ingredient is already in another preparation (cold remedy).
  • With pre-existing conditions (stomach, kidney, heart, liver) and continuous medication, ask first.
  • NSAIDs with/after food for better stomach tolerability.
  • Do not combine different NSAIDs.
  • In children no ASA with feverish infections; use age-appropriate preparations.
  • In pregnancy only after consulting a doctor (paracetamol preferred).
  • Do not combine with alcohol.
  • With persistent pain (over a few days) have it medically clarified.

14. How brite helps you with painkillers

With over-the-counter painkillers in particular, the typical mistakes happen unnoticed: accidental double dosing (paracetamol in a cold remedy + a tablet), risky combinations (NSAID + blood thinner), creeping overuse. brite helps exactly there:

Interaction check

Check whether an over-the-counter painkiller is compatible with your other medications (blood thinners, blood-pressure agents, cortisone).

Medication plan

All medications in one place, to avoid accidental double dosing (e.g. paracetamol in several preparations).

Intake tracking

Document painkiller use and recognize too-frequent use (risk of overuse headache) early.

Health record

Document pain, triggers and effect — helpful for the doctor's appointment.

Digital medication plan

Clearly laid out for the GP and pharmacy.


brite: combine painkillers safely

Prevent accidental double dosing, check interactions with blood thinners or blood-pressure agents, recognize overuse headache early — avoid the typical painkiller pitfalls.

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FAQ: common questions about painkillers

It depends on the complaints. Ibuprofen additionally has an anti-inflammatory effect and is therefore often better for inflammatory pain (toothache, period, joint pain), but burdens the stomach, kidney and heart more. Paracetamol is gentler on the stomach and kidney and good for headaches and fever, but has barely any anti-inflammatory effect and a liver risk with overdose. With a sensitive stomach or in pregnancy, paracetamol is often the preferred choice (after consultation).
Paracetamol is by far the gentlest on the stomach, because it is not an NSAID and barely burdens the gastric lining. Among the NSAIDs, ibuprofen tends to be more stomach-friendly than diclofenac and above all ASA. Anyone with a sensitive stomach, previous stomach ulcers, or who additionally takes cortisone/blood thinners, should avoid NSAIDs or only use them after consultation and with stomach protection.
In certain situations the combination is possible, because the two work differently — but only on the recommendation of a doctor or pharmacist and for a limited time. Two NSAIDs, by contrast, must not be combined (e.g. ibuprofen + diclofenac or + ASA), since only the risks add up. It is also important to check whether an active ingredient is already contained in another preparation (e.g. a cold remedy).
In children and adolescents with feverish, especially viral infections, ASA can trigger the rare but life-threatening Reye's syndrome (severe damage to the brain and liver). This is why ASA is not used in children to treat fever and pain. Suitable for children are paracetamol and ibuprofen in an age-appropriate dose and form — as instructed by a paediatrician or pharmacy.
At the correct dose, paracetamol is very safe and well tolerated. The danger lies in overdose: even exceeding the maximum daily dose can severely damage the liver — the safety margin is smaller than many think. Particularly risky are accidental double doses (paracetamol is in many combination preparations), pre-existing liver disease and regular alcohol consumption. Always keep strictly to the maximum dose.
For inflammatory joint, muscle and back pain, NSAIDs like ibuprofen or diclofenac are often the most effective, because they additionally have an anti-inflammatory effect. For local complaints (bruise, strain, a single joint), diclofenac gel is a gentle alternative, since it barely gets into the body. With persistent or severe back pain, the cause should be medically clarified.
Yes — paradoxically, using painkillers too often can itself trigger headaches (medication-overuse headache). The risk exists when pain or migraine medications are taken on more than about 10 to 15 days a month. A vicious circle develops: more painkillers, more headaches. Anyone who frequently reaches for painkillers should have it medically clarified.
Paracetamol is considered the painkiller of choice in pregnancy, but should only be used after consulting a doctor and as briefly and at as low a dose as possible. NSAIDs like ibuprofen and diclofenac should be avoided especially in the last trimester, since they can harm the unborn child. ASA at a pain dose is also not suitable. With pain in pregnancy, always seek medical advice.
Over-the-counter painkillers are intended for short-term use. As a rough orientation, the rule is often: without medical advice, no longer than about 3 to 4 days for fever and no longer than a few days for pain. Anyone who needs painkillers for longer or regularly should have the cause medically clarified — both because of possible serious causes and because of the risks of continuous use.
Yes, that can happen. Anyone taking low-dose ASA to prevent heart attack/stroke should know that ibuprofen can weaken the heart-protecting (clotting-inhibiting) effect of ASA if it is taken at the wrong time. A doctor's consultation is important here — often a time gap is recommended, or another painkiller (e.g. paracetamol) is preferred.

Related topics

Sources

  1. IQWiG — gesundheitsinformation.de: Schmerzmittel, NSAR, Paracetamol. gesundheitsinformation.de
  2. Arzneimittelkommission der deutschen Ärzteschaft (AkdÄ) — nichtopioide Analgetika. akdae.de
  3. Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM) — Sicherheitshinweise zu Schmerzmitteln. bfarm.de
  4. Deutsche Schmerzgesellschaft. schmerzgesellschaft.de
  5. S3-Leitlinie Behandlung von Schmerzen / DEGAM-Leitlinien zu Schmerz. awmf.org
Medical disclaimer: This article is for general information and does not replace advice from a doctor or pharmacist. Over-the-counter painkillers also have relevant risks and interactions. The choice, dose and duration of use should be clarified with a doctor/pharmacist in the case of pre-existing conditions, continuous medication, in pregnancy and in children. With persistent, severe pain or pain associated with warning symptoms, seek medical help. If an overdose is suspected (above all paracetamol), seek medical help immediately. Last updated: May 2026.