The safe use of over-the-counter painkillers

The largest group of over-the-counter painkillers are the non-steroidal anti-inflammatory drugs (NSAIDs). As their name suggests, they also reduce inflammation but – unlike other anti-inflammatory medicine – do not contain steroids. Over-the-counter NSAIDs are used in the treatment of many different kinds of pain, including headaches, period pain and toothache. NSAIDs also reduce inflammation and lower fever.

There are more than ten different NSAIDs, but not all of them are available without a prescription. Sometimes only lower doses are available without a prescription. Higher doses have to be prescribed by a doctor. In Germany and other countries, the following NSAIDs are available over the counter:

• Acetylsalicylic acid (the drug in medicines like "Aspirin") (in doses of up to 500 mg per tablet)
• Diclofenac (up to 25 mg per tablet)
• Ibuprofen (up to 400 mg per tablet)
• Naproxen (up to 250 mg per tablet)

These medications are also the most commonly used NSAIDs.

Acetaminophen (paracetamol) is another very widely used painkiller that is available without a prescription. While also relieving pain and lowering fever, it doesn't reduce inflammation (unlike NSAIDs).

In some medications acetaminophen is combined with an NSAID – for instance, with acetylsalicylic acid. Caffeine is sometimes added too. It isn't clear whether these kinds of combinations have any advantages or disadvantages over using the different drugs separately. There are no good-quality studies comparing combination medications with individual drugs.

NSAIDs inhibit the action of certain enzymes known as cyclooxygenases or COX enzymes. For this reason, NSAIDs are sometimes also referred to as COX inhibitors. COX enzymes play an important role in the production of certain hormone-like substances, such as the prostaglandins. These have various jobs, including triggering and regulating the reactions in an inflammation (pain, swelling and fever). Other processes in our bodies, including blood clotting and the production of stomach acid, are also influenced by these substances. There are two different COX enzymes:

• COX-1 is mainly found in the stomach, kidneys and blood platelets. It is responsible for maintaining a natural balance of the processes it influences.
• COX-2 is mostly made in the parts of the body where inflammations occur. It increases reactions such as pain, swelling and fever.

By inhibiting the action of both COX enzymes, over-the-counter NSAIDs can reduce pain, fever and inflammation. But other processes that are regulated by the COX enzymes are also slowed down. That can cause side effects, especially stomach problems.

Not all painkillers have the same side effects, though: Acetylsalicylic acid (the drug in medicines like Aspirin) has a stronger effect on the COX-1 enzyme, for instance, while diclofenac mostly inhibits COX-2.

Certain prescription-only NSAIDs only (selectively) inhibit the COX-2 enzyme, so they are considered to be more gentle on your stomach. But they can still cause stomach problems and other side effects, for example affecting the heart.

It is still not clear exactly how acetaminophen (paracetamol) works. There are various potential explanations – for instance, that it may affect hormone-like substances too (like NSAIDs do).

The risk of side effects and complications can be reduced by using the lowest dose of painkillers possible. It is generally important not to exceed the maximum single dose or the maximum daily dose. The information in the following table applies to Germany but may be very similar in other countries.

So if someone has a packet of 400 mg ibuprofen tablets, for instance, they should not take more than three tablets per day (24 hours).

This information applies when the medications are used without a prescription. It may be possible to take some of the drugs at a higher dose when prescribed by a doctor.

Different NSAIDs shouldn't be combined with each other. But an NSAID can be combined with acetaminophen (paracetamol) if one medication alone isn't effective enough.

The most common side effects of NSAIDs affect the stomach. They range from minor problems like indigestion and stomach ache to more serious problems like gastritis, ulcers and bleeding in the stomach or bowel (gastrointestinal bleeding). The risk of complications can be significantly reduced by using other medication to protect the stomach. Proton pump inhibitors such as omeprazole or pantoprazole are typically used for this purpose. But over-the-counter painkillers very rarely lead to serious side effects if they are taken for a short time only.

Several analyses of studies in recent years have also shown that certain NSAIDs, such as diclofenac, increase the risk of cardiovascular (heart and blood vessel) disease. But that is mainly if you take high doses over a long period of time. Still, it may be a good idea for people who are at higher risk of cardiovascular disease, or already have cardiovascular disease, to take low doses of ibuprofen or naproxen, for example, rather than diclofenac.

NSAIDs like acetylsalicylic acid (the drug in "Aspirin") may cause breathing problems. People who have chronic asthma should talk to their doctor about which painkillers to use. Like in people who have cardiovascular disease, acetaminophen (paracetamol) may be a suitable alternative here.

A number of personal factors increase the likelihood of NSAIDs causing problems. The risk of developing stomach or bowel problems is greater if you

• are over the age of 65,
• currently have a stomach ulcer or gastritis, or had one of them in the past,
• have chronic inflammatory bowel disease (Crohn's disease or ulcerative colitis),
• take several different NSAIDs at once, or are already taking low-dose acetylsalicylic acid for the prevention of complications following a heart attack or stroke, or
• are taking anticoagulant (anti-clotting) medication, steroid medication or SSRI antidepressants too.

NSAIDs also increase the risk of heart attacks or strokes, particularly in people who have already had one. These complications are more likely if you already have other kinds of cardiovascular disease or if you have risk factors such as high blood pressure. In people who have decreased kidney function, taking NSAIDs can increase the risk of acute kidney failure. It is especially important for them to avoid taking too high a dose.

NSAIDs aren't suitable for people with advanced kidney disease. Acetaminophen (paracetamol) is then an alternative option. People who have a stomach ulcer or severe cardiac insufficiency (heart failure) shouldn't take NSAIDs either. Pregnant women are only allowed to take certain NSAIDs during certain weeks of pregnancy. The risk of NSAID-related side effects is also greater in people who have asthma. It is best to consult your pharmacist or doctor if you have any questions.

Acetaminophen (paracetamol) isn't suitable for people who have liver disease. This is because it is broken down by the liver and can cause severe liver damage. It is also not suitable for people who have problems with alcohol abuse. People who have severely decreased kidney function should wait eight hours between taking the tablets.

The doses for children are different (sometimes much lower), depending on their age and weight. Some of the above-mentioned medications aren't suitable for children and should only be given to them if their doctor says it's okay.

For example, acetylsalicylic acid (e.g. in Aspirin) isn’t suitable for children under the age of twelve who have a viral infection with a fever. This is because it can cause a rare but life-threatening disease (Reye's syndrome) that leads to severe brain and liver damage.

Side effects like mild indigestion aren't a cause for concern. But you should see a doctor if you have frequent or severe stomach pain, or if you notice signs of bleeding in the stomach. These include

• black-colored stool (poop) and
• anemia symptoms such as exhaustion, shortness of breath during physical activity, or pale skin.

In rare cases, ulcers can damage a large blood vessel and result in a lot of blood loss within a short space of time. Vomiting blood (red or black-colored vomit) is a sign of this complication. Another rare complication known as a perforation can occur if a stomach ulcer results in a hole in the wall of the stomach. This causes sudden severe stomach pain. Heavy bleeding in the stomach and perforation of the stomach are life-threatening conditions. If you recognize signs of these or other serious complications, it's important to immediately make an emergency call (112 in Germany and many other countries, 911 in the U.S.)

You can lower the risk of painkiller-related side effects and complications by paying attention to the package insert and

• always taking "as little as possible, as much as necessary,"
• only taking painkillers for as long as really needed,
• being aware of possible interactions with other medications, and
• checking whether you have any risk factors or medical conditions that mean that certain painkillers aren't suitable for you.

Painkillers can also interact with other medications. It is called a "drug-drug interaction" if two medications influence each other – for instance, if they increase, weaken or cancel out their effects. As a result, the medications may no longer work properly or the risk of complications might increase.

NSAIDs can interact with various medications. For instance, taking them together with certain medications that suppress the immune system (cyclosporine and tacrolimus) increases the risk of kidney damage. This is also true if you take NSAIDs together with diuretics or certain blood-pressure-lowering drugs known as ACE inhibitors and angiotensin II antagonists (sartans). NSAIDs can increase the effect of anti-clotting medications (anticoagulants) such as clopidogrel and Marcumar, which may lead to bleeding.

Taking acetaminophen (paracetamol) together with certain medications can increase the risk of liver damage. Alcohol can increase this risk too, so you should avoid alcohol when using acetaminophen.

Alcohol and various medications, as well as malnutrition, can affect the breakdown of acetaminophen in the body and lead to an overdose of this painkiller.

The possible drug-drug interactions of a medication are listed in the accompanying package insert. It is best to consult your doctor or pharmacist if you have any questions.