ChemMatters | FEBRUARY/MARCH 2018 9
One of These
Painkillers Is Not
Like the Others
Acetaminophen is a fourth type of common OTC painkiller, but it’s not
an NSAID. It only relieves pain and fever,
whereas NSAIDs reduce swelling, inflammation, and pain. Acetaminophen does not
inhibit COX- 1 or COX- 2, but it does inhibit
enzymes responsible for the production of
other prostaglandins from PGH2 (further
down the chemical reactions pathway
shown in Fig. 1). While acetaminophen
prevents the formation of prostaglandins
that cause fever and pain, it doesn’t inhibit
the production of prostaglandins that are
responsible for swelling and clotting.
The Important Role of Enzymes
Enzymes are biological catalysts that speed up chemical reactions by providing a new path that
has a lower activation energy.
NSAIDs work by interacting with enzymes, and this is
actually how many other drugs work, too. For example,
penicillin and the human immunodeficiency virus (HIV)
drug ritonavir work by blocking enzymes.
Without enzymes, virtually all chemical reactions
would not occur under the mild conditions present in
living organisms or would occur at very slow rates.
Enzymes are located inside and outside a cell, and
also within a cell’s membrane. Inside a cell, enzymes
enable most chemical reactions to happen, and without
enzymes, a cell would be a lifeless bubble.
Let’s look at three common OTC
NSAIDs: 1) aspirin, 2) naproxen, and
3) ibuprofen. You could take any of these
drugs if you had pain in your body, and
that is why they are called painkillers.
Even though you take these drugs for
similar effects, these products have different chemical structures. As a result, they
relieve different types of pain and cause
different side effects in people.
Naproxen and ibuprofen may have side
effects that include digestive system irritation and bleeding from the lining of the
stomach. Aspirin’s side effects include
digestive system ulcers (internal sores)
Aspirin is not recommended for chil-
dren and teens, because its use has
been linked to a condition called Reye’s
syndrome, a disorder that could cause
life-threatening liver and brain swelling.
Some people also prefer to take naproxen
over other NSAIDs because its pain-relieving effects last longer than other
OTC NSAIDs, including ibuprofen.
However, despite their differences,
naproxen, ibuprofen, and aspirin are
similar in their ability to interfere with
the same biochemical
(and painful!) pathway.
Next time you have a
headache or accidentally
stub your toe near that
same old spot on your
couch and open your
medicine cabinet to reach
for your NSAIDs, you may
want to think about these
rushing in your blood and
the NSAIDS taking away
your pain by preventing
your cells from producing
more prostaglandin molecules. What would your life
be like without NSAIDs?
Bakalar, N. The Limits of Tylenol for Pain Relief.
New York Times/blogs/ well.com, April 1, 2015:
Landau, E. From a Tree, a ‘Miracle’ Called Aspirin.
CNN.com, Dec 22, 2010: http://www.cnn.
Mehta, A. Aspirin. Chemical & Engineering News,
June 20, 2005, 83 (25), p 3: https://cen.acs.org/
Rachele Hendricks-Sturrup is a science writer who
lives in Hollywood, Fla. This is her first article in
Figure 1. Prostaglandins can trigger unpleasant
bodily processes such as pain, inflammation,
and fever. NSAIDs, such as aspirin, prevent the
enzyme cyclooxygenase from catalyzing the
conversion of arachidonate to the prostaglandin,
PGG2. This blocks a cascade of biochemical
reactions that produce prostaglandins.
How NSAIDs work
The Arachidonic Acid Pathway
Naproxen ( 2) Ibuprofen
Acetylsalicylic acid (aspirin) ( 1)