Whatever Happened to "Old" Ex-Lax?

By Josh Bloom — Feb 23, 2026

For most of the 20th century, you could buy a laxative that looked like a chocolate bar. This seemed like a good idea until people started treating it like a chocolate bar. The story of “old” Ex-Lax is part dorm folklore, part chemistry lesson, and mostly useless. Enjoy it anyway.

Image: ACSH

If you're sufficiently old and have ever lived in a dorm, chances are you're either aware of this prank. Or the victim of it:

People smoke weed.
Then they get the munchies.
Brownies are a common and effective remedy for the munchies.
This is all well and good provided that the brownies are, too.
But sometimes they're not.

In the 1970s, this was a common prank and means of revenge. You know the story, real or imagined: Someone gets plenty tired of having his brownies stolen. After smoking more weed, he gets help from Betty Crocker and the local pharmacy and bakes a batch of nuclear colon bombs. After smoking more weed, he leaves them out, preferably with a note asking people not to eat them. Then he smokes more weed.

Ex-Lax, ca. 1970, bears a striking resemblance to "real" chocolate. That's because it is just that.

The results are predictable (and gentle!). I'm not going into the stories. They all end the same.

But there are some damn funny comments out there.

A Facebook page recently asked readers whether they had ever been a victim. The internet, as always, did not disappoint:

"No, but I did eat at Sonic Burger."

And another guy, apparently a slow learner, added:

“I never fell for it. After the second time.”

And be careful who you date:

"I love this trend. It's giving girls so many unique ideas to deal with useless men."

What happened to "old" Ex-Lax?

You know the FDA expression GRAS (Generally Recognized as Safe)? In the late 1990s, the FDA booted phenolphthalein – the active ingredient – into the "not generally recognized as safe and effective" bucket, marking the end of decades of phenolphthalein use in the US. This happened because the chemical was found to be carcinogenic when given to rats in high doses. And there were plenty of alternatives, so flushing phenolphthalein wasn't a big deal.

Phenolphthalein is a rather interesting chemical, and you know who to call on when it's time to discuss stuff like this – Steve and Irving – the cantankerous hosts of The Dreaded Chemistry Lesson From Hell^TM!!

WTH? Where is Steve? After all, it takes two hosts to introduce TCLFH^TM. The answer? Irving's been eating Brussels sprouts again (after all, hell is where the damn things belong), and Steve couldn't take the stench. He retreated to Purgatory until the air clears.

Cool stuff about phenolphthalein:

Its name comes from the two ingredients that are used to make it: phenol and phthalic anhydride.

It's an old-fashioned pH indicator. In acidic, neutral, or slightly basic solutions, it is colorless. At or above pH 8.2, it turns pink. Add acid, and the color disappears. It's rarely used anymore. pH paper and analytical instruments do a better job.

(Left) Phenolphthalein (closed form) at or below pH 8. (Right) Open form pH ~8-12

Quiz! Why is the open form colored?

Another quiz: At very high pH, it becomes colorless again. Why?

Aside from its toxicity, the Ex-Lax candy bar was doomed anyhow. The FDA has become increasingly concerned about drugs that can be mistaken for candy. It is reasonable to say that the old Ex-Lax bars were candy. The bars weighed about 20 grams. The active drug was measured in hundreds of milligrams. In other words, it was a chocolate bar with a little schmootz in it.

Doesn't this make you wonder about the proliferation of gummies? Today, you can get antihistamines, laxatives, melatonin, and even cold remedies in gummy form. And this list doesn't even include the huge number of cannabis chemicals. Perhaps the FDA is chewing out of both sides of its mouth.

That's about all I have on Ex-Lax. If you're concerned about Steve, worry not. He's back, having successfully lobbied the Hell HOA for a rule change. All is well.

Josh Bloom

Director of Chemical and Pharmaceutical Science

Dr. Josh Bloom, the Director of Chemical and Pharmaceutical Science, comes from the world of drug discovery, where he did research for more than 20 years. He holds a Ph.D. in chemistry.