Diphenoxylate Side Effects

The U.S. Drug Enforcement Agency, or DEA, classifies substances according to the potential for abuse. The DEA has categorized diphenoxylate as a schedule II narcotic, which means it carries a high risk for abuse and physical or mental dependence. In doses effective for its prescribed use as an anti-diarrheal medication, diphenoxylate does not normally cause addiction. However, when used at high doses, this drug does produce euphoria and, with continued use at high doses, physical dependence. Diversion is the illegal distribution, abuse, or unintended use of prescription drugs. Individuals taking prescription opioids should store diphenoxylate where it cannot be discovered, used or stolen by persons intending to divert it to criminal or recreational use.

Diphenoxylate, like all medicine, has the potential to cause side effects. Many people experience no, or minor, side effects from taking this drug. Most side effects are not serious and disappear after a few days. A few side effects are serious and require the attention of a medical professional.

Diphenoxylate, like all medications, may cause side effects. The most common side effects associated with this medication are not serious. Continue taking diphenoxylate but contact the prescribing physician if the following side effects become intolerable or if they do not go away on their own:

  • Blurred Vision
  • Constipation
  • Decreased Sweating
  • Difficulty Sleeping
  • Dizziness
  • Drowsiness
  • Dry Mouth, Nose or Skin
  • Headache
  • Loss of Appetite
  • Loss of Taste
  • Nausea
  • Nervousness

Some side effects are serious, requiring immediate medical attention. Stop taking diphenoxylate immediately and contact a doctor if you experience serious side effects, including:

  • Abdominal Bloating or Swelling
  • Agitation or Excitement
  • Changes in Heartbeat
  • Confusion
  • Delirium
  • Difficulty Urinating
  • Exaggerated Sense of Well-Being
  • Fast or Irregular Heartbeat
  • Fever
  • Hallucinations
  • Numbness of the Hands or Feet
  • Severe Diarrhea
  • Severe or Prolonged Restlessness
  • Severely Enlarged Pupils
  • Speech Problems
  • Unusual Weakness
  • Vision Problems
  • Vomiting

Central Nervous System Side Effects

Diphenoxylate toxicity usually presents in two phases. Early signs are due to poisoning and include fever, high blood pressure, flushed or dry skin, dilated pupils, rapid breathing, rapid heart rate, disorientation or hallucinations. The early signs typically last for two to three hours. Children are especially susceptible to experiencing these early signs after taking diphenoxylate.

Later signs of diphenoxylate toxicity are associated specifically with opioid toxicity. The second phase usually follows the early phases immediately but can start as late as 36 hours after the initial phase ends. These late signs include lethargy, extreme drowsiness, poor reflexes, constricted pupils or even coma.

Diphenoxylate side effects affecting the central nervous system, or CNS, usually indicate potentially fatal toxicity. Respiratory depression is one of the more significant CNS side effects of diphenoxylate. Respiratory depression is a state where the lungs do not adequately exchange oxygen for carbon dioxide.

Gastrointestinal/Genitourinal Side Effects

Diphenoxylate affects the way the digestive system works. This drug may worsen or prolong diarrhea associated with some drugs or infectious agents, such as E. coli and salmonella. This medication can cause constipation. Increasing fluid intake usually softens stools and relieves constipation. Diphenoxylate may also cause serious digestive problems, such as toxic megacolon or paralytic ileus. Patients with a history of ulcerative colitis should discontinue diphenoxylate if they experience abdominal pain after taking this medication. Diphenoxylate causes distention, or abdominal swelling, in about 6 percent of patients. Diphenoxylate may cause impotence in some male patients or urinary retention in men or women.

Hypersensitivity Some patients may be hypersensitive to diphenoxylate. Hypersensitivity side effects include:

  • Hives
  • Itching
  • Swelling beneath the Skin
  • Low Blood Pressure
  • Abdominal Pain
  • Rapid Breathing
  • Swelling of the Gums
  • Nausea and Vomiting