A dosage unit with not more than 2.5 mg Diphenoxylate and not less than 25 mcg Atropine Sulfate per dosage unit is scheduled as which?

• A. Schedule II
• B. Schedule III
• C. Schedule IV
• D. Schedule V

Answer: (D)

The schedule depends on the abuse potential of the drug and how the specific fixed-dose combination is formulated. Diphenoxylate by itself is a narcotic-type antidiarrheal, so it has high abuse potential and is controlled accordingly. When it’s combined with atropine and the product is limited to not more than 2.5 mg of diphenoxylate per dosage unit and at least 25 mcg of atropine per dosage unit, this lowers the abuse risk of the mixture enough to place it in Schedule V.

The atropine acts as a deterrent to misuse, so the fixed-dose combination with these per-dose limits is recognized as having a much lower potential for abuse than higher-dose or unlabeled forms. That’s why this specific formulation is categorized as Schedule V rather than a higher schedule. If the per-dose amounts exceeded those thresholds, the product could fall into a higher schedule.