The Challenge of Relieving Pain

by Food and Drug Administration (FDA)

The lucky among us have only an occasional headache. For others, pain is a constant, though unwelcome, companion.

Relieving pain is sometimes simple, sometimes impossible. It depends on the source of the pain and it may also depend on the person.

Everyday Aches and Pains

There are three main nonprescription choices for pain relief — aspirin, acetaminophen (Datril, Tylenol and others), and ibuprofen (Motrin IB, Advil, Nuprin, and others). All three block the production of chemicals called prostaglandins, which the body usually releases when cells are injured. Prostaglandins are believed to play an important role in the pain, heat, redness, and swelling that occur following tissue damage.

So what's the best choice for your headache, pulled muscle, or menstrual cramps?

When it comes to mild, nonspecific pain, headaches, or menstrual discomfort, "all three [nonprescription pain relievers] are quite useful," says Patricia Love, M.D., a rheumatologist with FDA's Center for Drug Evaluation and Research. "There are probably persons who are not able to detect a difference in the effectiveness of the OTC products."

It has been suggested, Love says, that aspirin or ibuprofen may be more effective than acetaminophen for pain caused by inflammation or mild menstrual discomfort because they have more prostaglandin-blocking effects. (For more information on menstrual cramps, see "Taming Menstrual Cramps" in the June 1991 FDA Consumer.) "Our best advice at present is that, for mild pain, individuals may use what works best and is safe for them," says Love.

In other words, what doesn't cause them problems.

Because prostaglandins play a role in protecting the stomach lining from being attacked by the acid of digestive fluid, aspirin, ibuprofen, and, apparently to a lesser extent, according to Love, acetaminophen may cause stomach irritation, ulcers or bleeding. "If you have a history of stomach disorders, first talk to your doctor [before taking a nonprescription pain reliever]," says Love.

For some people who take aspirin, stomach irritation may be decreased by taking either enteric-coated aspirin, buffered aspirin, or other modified aspirin derivatives such as choline salicylate or magnesium salicylate.

Buffered aspirin contains an ingredient that neutralizes some of the digestive system's acid and, therefore, may produce less irritation than plain aspirin.

Coated aspirin dissolves mainly in the intestine. (Uncoated aspirin dissolves in the stomach.) In theory, that difference may mean less stomach irritation says Love. But, she adds, it still depends on an individual's metabolism. For example, some people can't digest the coating, so while they don't get any stomach irritation, they don't get any benefit either. The aspirin passes out of the body undigested and unabsorbed.

People who can't take aspirin because of allergic reactions (e.g., rash, asthma, anaphylaxis) generally can't take ibuprofen either. For them, acetaminophen may be the only nonprescription choice.

"Persons with medication allergies should discuss the use of any nonprescription medication with their doctor," Love says.

She adds that all three drugs have the potential to cause liver damage, although liver toxicity is much less common than gastric ulcers or bleeding.

FDA is reviewing recent studies that suggest an association between use of all three nonprescription pain relievers and kidney disease. But the agency says that not enough is known yet about these possible associations to make any changes in current recommendations for use for healthy individuals.

"I think one of the important safety issues in choosing a medication is it's not just whether or not you have minor pain, but what is your medical history on top of the minor pain," says Love. "People who have specific disorders — kidney disease, heart disease, bleeding problems, liver disorders, medication allergies — should talk to their physicians."

Acute Pain from Injury or Surgery

When the pain becomes too much to bear, or is the result of a serious injury or surgery, relief requires stronger medicine and a doctor's prescription. One class of frequently prescribed pain relievers is nonsteroidal anti-inflammatory drugs, often abbreviated NSAIDs. (The three nonprescription pain relievers are also NSAIDs, according to Love, although acetaminophen is not commonly referred to by that term.)

Prescription NSAIDs are given at higher doses than the nonprescription types, but the mechanism for pain relief is the same — blocking the production of prostaglandins. (For more information on NSAIDs, see "How to Take Your Medicine: Nonsteroidal Anti-Inflammatory Drugs" in the June 1990 FDA Consumer.)

Opiate drugs are another class of pain-relieving prescription drugs. Commonly prescribed opiates include morphine, codeine, hydromorphone (Dilaudid), and meperidine (Demerol). (In some states, some forms of codeine are sold without a prescription in limited amounts.) Most of these drugs are derived from opium, the juice of the poppy flower.

Opiate drugs work by altering the transmission of pain messages in the brain and spinal cord, blocking pain messages or altering their character.

The pain-blocking action of the opiates can be enhanced by taking aspirin, ibuprofen or acetaminophen at the same time as the opiate. This hits pain with a "double-whammy." The NSAIDS block the pain at the site of injury, while the opiates suppress in the brain any remaining pain.

Unfortunately, the effect of opiates on the brain isn't limited to pain control. Opiates can cause drowsiness, nausea, constipation, and unpleasant mood changes in some people. However, sometimes simply trying a different opiate may be all that's needed to reduce these side effects.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.