I never know which type of over-the-counter pain medication to use for different types of pain, like headaches, sprained ankles or sore muscles. Which works best for these unique situations?

When you have aches and pains, it can be challenging to decide which over-the-counter pain reliever is best for your affliction – Advil, Aleve, Panadol, Motrin?

The choice, experts say, comes down to just two classes of medication: acetaminophen and nonsteroidal anti-inflammatory drugs (or Nsaids).

Each addresses pain in its own way, said Dr Mary Lynn McPherson, a professor at the University of Maryland School of Pharmacy. And not all types of pain respond equally well to both, she added.

Here is how to tell what types of pain these drugs are most effective at relieving and how to use them safely.

How they work

Nsaids, which include ibuprofen (Advil, Motrin), naproxen (Aleve) and aspirin (Bayer), help relieve pain by rushing to sites of inflammation throughout the body, said Dr Katherin Peperzak, medical director of the Center for Pain Relief at the University of Washington Medical Center.

They reduce or block two enzymes called COX-1 and COX-2. This action hinders the production of prostaglandins, chemicals that contribute to swelling, inflammation and pain, she said.

Acetaminophen (Panadol, Tylenol), on the other hand, is dispatched to receptors in the brain and the spinal cord, but what it does from there is a little more mysterious.

“We’re not 100 per cent sure how the heck that bad boy works,” Dr McPherson said.

One theory is that it also reduces certain COX enzymes, Dr Peperzak said. But acetaminophen does not target inflammation like Nsaids do, Dr McPherson added.

When to use them

Nsaids and acetaminophen can relieve many of the same types of pain. But there are pros and cons to each.

Nsaids are best at treating inflammation-related pain that occurs anywhere in the body, whether it is localised to one spot (as with migraine headaches, toothaches, muscle strains or cuts) or spread throughout (as with arthritis pain).

“If you’ve got redness, heat or swelling, or it’s an acute injury, there’s probably some inflammation,” Dr Peperzak said, and your pain is a good candidate for Nsaids.

All Nsaids work similarly, so choose the one that is most effective for you, said Dr F. Michael Ferrante, director of the Pain Management Center at the University of California, Los Angeles.

Naproxen (sold as Aleve), however,...