Let’s talk about loperamide. We reach for the stuff every time food poisoning sends our bowels running, but the anti-diarrheal — we know it as Imodium — has also gained a dangerous reputation among opioid addicts as a quick fix. The New York Times called it the “poor man’s methadone” — a cheap and desperate high that, at abnormally large doses, can send heartbeats racing to the point of fatal exhaustion. How did America’s favorite constipator become the drug of last resort for opioid addicts?

The infamous bathroom scene in Trainspotting explains everything: “Heroin makes you constipated,” explains Renton as he’s crouched on the worst toilet in Scotland, waiting for his anally delivered drugs to take effect. “The heroin from my last hit was fading, and the suppositories had yet to melt.” Loperamide, like heroin, morphine, and methadone, gets people high because it works on the body’s opioid receptors, which control the runs or induces euphoria, depending on where they are.

But loperamide’s effects aren’t nearly as potent. At least, they shouldn’t be — not when the drug is taken at the correct dose. Four caplets of Imodium, at eight milligrams each, delivers just enough loperamide to opioid receptors in the large intestine to get it to relax instead of squeezing its contents out through the backside. What this does is buy the gut more time to suck moisture out of the digested food so that, by the time it does make its exit, it more or less resembles a solid and not a fucking waterfall.

The problem is that opioid addicts aren’t taking the standard daily dose. They’re taking about 100 two-milligram tabs every day for weeks at a time. At crazy high concentrations, the safeguards against the loperamide brain high are moot. Normally, proteins in the gut prevent it from leaking into the network of nerves connecting the brain and spinal cord, and the liver’s detoxifying abilities pick up the slack. But at concentrations 25 times higher than normal, the body gets overwhelmed.

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Loperamide, like heroin, makes you constipated and will probably kill you if you overdo it.
Loperamide, like heroin, makes you constipated and will probably kill you if you overdo it.

Once loperamide pushes its way to opioid receptors in the brain, it pretty much has the same euphoric and gloriously pain-killing effects as other narcotics, like morphine. The FDA first classified it as a schedule II drug, lumping it together with cocaine and methadone, after approving it in 1976. It wasnt being abused back then — sure, studies on rhesus monkeys showed it caused mild physical dependence — but it was deemed safe enough to be classified as a prescription medication and, later, a decontrolled over-the-counter drug.

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A recent article in the journal Annals of Emergency Medicine, reporting two loperamide overdose deaths, is calling that decision into question. As the nationwide crackdown on prescription painkillers intensifies, opioid fiends — and those trying to kick their addiction — are looking to get their fix any way they can, side effects be damned. But loperamide is not a drug to take lightly: In addition to dizziness, vomiting, and stomach pain, it can also cause life-threatening heart arrhythmias and dangerously slow breathing. But these risks, together with the obvious discomfort of being intestinally backlogged for weeks, haven’t stopped users from sweeping Imodium off pharmacy shelves, further emphasizing how deadly serious America’s opioid addiction problem has become.