Diphenoxylate is a medication used to manage diarrhea in individuals 13 years of age and older. It helps reduce the frequency and urgency of bowel movements.
Diphenoxylate’s Classification
Diphenoxylate is an opioid, chemically related to meperidine. Its legal classification is complex due to its formulation. When diphenoxylate is found alone, it is classified as a Schedule II controlled substance under the Controlled Substances Act (CSA) in the United States, indicating a high potential for abuse.
The common formulation, such as Lomotil, combines diphenoxylate with a small amount of atropine. This combination changes its classification. This combination is classified as a Schedule V controlled substance by federal regulation. Schedule V drugs are considered to have the lowest potential for misuse among controlled substances, resulting in very limited psychological or physical dependence. This lower scheduling is a direct result of the addition of atropine, which is intended to discourage abuse.
How Diphenoxylate Works
Diphenoxylate functions as an opioid agonist, targeting mu opioid receptors in the gut’s enteric nervous system. By binding to these receptors, it slows intestinal contractions and prolongs the transit time of contents through the gastrointestinal tract. This action allows the intestines more time to absorb water from the stool, helping to solidify loose bowel movements and alleviate diarrhea.
Atropine is added to deter misuse. Atropine is an anticholinergic medication that, in higher doses, causes unpleasant side effects such as dry mouth, blurred vision, and a rapid heart rate (tachycardia). While atropine does not possess anti-diarrheal properties, its presence is intended to create discomfort if an individual attempts to take more than the prescribed dose. This mechanism discourages individuals from consuming large quantities of the drug to achieve opioid-like effects.
Understanding Potential for Misuse
Despite its Schedule V classification and the inclusion of atropine, diphenoxylate, particularly the combination product, still carries a potential for misuse and dependence. Although not addictive at prescribed therapeutic doses, taking very high doses, such as 100-300 mg per day (equivalent to 40-120 tablets), can produce euphoric effects similar to codeine. This can lead to physical dependence and opioid withdrawal symptoms upon cessation.
Signs of misuse or overuse include taking more than the prescribed amount, seeking multiple prescriptions, or using the medication for non-medical reasons. If usage is prolonged and at high doses, stopping the medication abruptly can trigger withdrawal symptoms such as anxiety, aching muscles, insomnia, nausea, vomiting, stomach cramps, and sweating. It is important to adhere strictly to medical advice and prescribed dosages to mitigate these risks.