Learn how over-the-counter painkillers work

There are two main types of over-the-counter (OTC) painkillers that you're likely to encounter: anti-inflammatories and non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen. We'll teach you all about them.

Anti-inflammatory NSAIDs like ibuprofen and naproxen work by blocking production of prostaglandins, which are chemicals that increase the sensitivity of nerve endings and create pain and inflammation. Chemical variations among NSAIDs can affect how well you absorb them, how quickly they act, and what side effects they have. If one doesn't work or bothers your stomach, try another.

• Acetaminophen relieves pain but not inflammation. It works by affecting the pain and temperature control centres of the brain.
• Acetaminophen is not an NSAID and is generally not as powerful as NSAIDs, especially for big pain. A review of 15 studies of people with osteoarthritis showed that pain decreased six more points (on a scale of 100) in people who took NSAIDs than in patients who took acetaminophen.
• However, when compared to NSAIDs, acetaminophen tends to be gentler on the stomach and have fewer side effects.
• Remember that Acetaminophen has a narrow safety margin. If you exceed the recommended daily limit, the risks skyrocket. Because of this, this painkiller causes more liver damage than any other drug.

• NSAIDs are most effective for arthritis pain, muscle aches, headaches, backaches, menstrual pain, and neck pain.
• Acetaminophen relieves the mild to moderate pain of headaches, muscle aches, menstruation, colds, sore throats, toothaches, backaches, and osteoarthritis, but it doesn't help lessen inflammation.
• Pain relievers that contain caffeine tend to work better for headaches, because the caffeine temporarily constricts the swollen blood vessels that cause pain. But when the medication wears off, the blood vessels can swell even more, potentially causing rebound headaches.

• Occasional use appears to be safe, and side effects don't generally occur unless NSAIDs are taken regularly for months or years.
• NSAIDs thin the blood, so they shouldn't be taken if you're on blood thinners or have anemia or a blood-clotting disorder.
• All NSAIDs block an enzyme that protects the stomach lining from the corrosive effects of stomach acid, which is why prolonged use can cause bleeding of the stomach lining or even create ulcers. In some cases, the bleeding is pronounced and even life-threatening.
• About one quarter of people who take NSAIDs regularly will have a stomach reaction like nausea or pain. Signs that your NSAID is causing stomach bleeding or an ulcer include stomach pain, dark black or tarry or bloody stools, and vomiting blood. Stop taking NSAIDs immediately and see your doctor if you experience any of these symptoms. Your doctor may prescribe another medication to take with NSAIDs that can protect the stomach lining.
• NSAIDs can also cause kidney damage.
• These medications have also recently been linked with a higher risk of heart disease, particularly in people who are already at risk.
• Guidelines from the American College of Rheumatology recommend acetaminophen as the first choice for people with osteoarthritis. But even acetaminophen can cause stomach irritation at doses of 3000 milligrams per day or more, and 4000 milligrams or more increases the risk of liver failure.

While painkillers can be a huge boon if you're suffering from pain, it's important to think of all painkillers as dangerous drugs and only take them if they're really helping. Use this guide to think more intelligently about the benefits and tradeoffs.