Yes, Lomotil is a controlled substance. The DEA classifies it as a Schedule V controlled substance, the lowest and least restrictive tier of the federal controlled substances schedules. This means you need a prescription to get it, but it carries fewer restrictions than higher-schedule drugs like oxycodone or Adderall.
Why Lomotil Is Controlled
Lomotil is prescribed to treat diarrhea, but one of its two active ingredients is an opioid. Each tablet contains 2.5 mg of diphenoxylate, which is chemically related to meperidine (a powerful prescription painkiller). At the standard dose used for diarrhea, diphenoxylate doesn’t produce the euphoria or pain relief associated with typical opioids. But at very high doses, it starts to produce effects similar to codeine. In clinical testing, people who took the equivalent of 40 to 120 tablets per day for 40 to 70 days developed opioid withdrawal symptoms when they stopped.
That opioid connection is the reason for the controlled substance classification. Diphenoxylate on its own, without any added deterrent, is actually classified as Schedule II, the same category as morphine and fentanyl. The combination product gets its lower Schedule V rating because of a built-in safeguard: atropine.
How Atropine Works as an Abuse Deterrent
The second ingredient in every Lomotil tablet is a tiny amount of atropine sulfate (0.025 mg). At the normal prescribed dose, this amount is too small to cause noticeable effects. But anyone trying to take large quantities of Lomotil to get an opioid high would also be swallowing large quantities of atropine, which triggers a set of deeply unpleasant symptoms: pounding or rapid heartbeat, dry mouth, flushed skin, difficulty urinating, restlessness, and even hallucinations.
This intentional pairing is the entire reason Lomotil sits in Schedule V rather than Schedule II. The atropine makes high-dose misuse physically miserable, which substantially lowers the drug’s abuse potential in practice.
What Schedule V Means for Your Prescription
Schedule V is the least restrictive controlled substance category. You still need a valid prescription from a licensed provider, and the pharmacy will keep a record of the dispensing. Federal law requires that Schedule V drugs only be distributed for a medical purpose, but the specific refill limits that apply to Schedule III and IV drugs (no more than five refills within six months) are not explicitly imposed on Schedule V substances under federal statute. In practice, your state may have its own rules governing refills, so the limits you encounter at the pharmacy can vary depending on where you live.
You won’t face the same level of scrutiny you’d encounter picking up a Schedule II painkiller. There’s no requirement for a new written prescription each time, and pharmacies generally handle Schedule V refills with minimal friction.
How Lomotil Compares to Imodium
Imodium (loperamide) is the other well-known anti-diarrhea medication, and it’s available over the counter with no prescription needed. Both drugs are technically opioid-based, but their legal status differs dramatically because of how they behave in the body.
Loperamide has very low absorption from the gut and barely crosses into the brain. It acts almost entirely on the intestines, which is why regulators determined it could be sold without a prescription. Diphenoxylate, by contrast, is a direct chemical relative of meperidine and can produce opioid-like central nervous system effects at high enough doses. That pharmacological difference is what keeps Lomotil behind the pharmacy counter while Imodium sits on the shelf.
Both drugs work by slowing the movement of the intestines, giving the gut more time to absorb water and firm up stool. For most cases of simple diarrhea, Imodium is the easier option to access. Lomotil is typically reserved for situations where a provider wants a prescription-strength option or where over-the-counter treatments haven’t been effective.
Current Scheduling Status
As of the DEA’s most recent published list (April 2026), diphenoxylate preparations containing 2.5 mg of diphenoxylate with 0.025 mg of atropine sulfate remain classified as Schedule V. There are no pending reclassifications. Pure diphenoxylate without atropine remains Schedule II, but that formulation isn’t what’s dispensed to patients.