What is causing loose motions in a patient taking Bupropion SR and a nicotine patch?

Bupropion is the Most Likely Cause of Loose Motions in This Patient

Bupropion SR is the most likely cause of the patient's loose motions, and temporary discontinuation or dose reduction should be considered while managing the gastrointestinal symptoms.

Medication Analysis and Likely Culprit

• Bupropion SR (150 mg twice daily) is the most probable cause of the patient's loose motions, as gastrointestinal disturbances including nausea and diarrhea are well-documented side effects 1, 2.
• While nicotine patches can cause gastrointestinal symptoms, diarrhea is less commonly reported with transdermal delivery compared to oral forms of nicotine replacement therapy 1.
• The other medications in the patient's regimen (baclofen, olanzapine, diazepam, thiamine, trihexyphenidyl, zolpidem, and melatonin) are less commonly associated with diarrhea as a primary side effect 2.

Mechanism of Bupropion-Induced Diarrhea

• Bupropion affects norepinephrine and dopamine reuptake, which can influence gastrointestinal motility and secretion 1.
• Gastrointestinal side effects of bupropion appear to be dose-related, with higher doses (such as the 300 mg/day this patient is taking) associated with more frequent adverse effects 1, 2.
• While constipation has been reported with bupropion (as in case reports), diarrhea and other gastrointestinal disturbances are more common side effects 3.

Management Approach

1. Consider temporary dose reduction or discontinuation:

   • If symptoms are severe or persistent, reducing the dose to 150 mg daily or temporarily discontinuing bupropion may be necessary 1, 2.
   • Gastrointestinal side effects often improve with dose reduction 1.

2. Hydration and supportive care:

   • Ensure adequate hydration to prevent dehydration from diarrhea 2.
   • Consider temporary use of antidiarrheal medications if symptoms are severe 2.

3. Monitoring:

   • Watch for signs of dehydration or electrolyte imbalances if diarrhea persists 2.
   • Monitor for worsening of psychiatric symptoms if bupropion dose is reduced or discontinued 1.

4. Potential alternatives:

   • If smoking cessation remains a priority and bupropion cannot be tolerated, consider nicotine replacement therapy alone without bupropion 1, 4.
   • Varenicline could be considered as an alternative for smoking cessation, though it also has gastrointestinal side effects, primarily nausea 1.

Important Considerations and Precautions

• Abrupt discontinuation of bupropion may lead to withdrawal symptoms or recurrence of depression, so any changes should be made gradually when possible 1.
• The patient is on multiple psychoactive medications (olanzapine, diazepam, bupropion), and changes to one medication may affect the overall psychiatric stability 2.
• The combination of bupropion and nicotine patch is an effective smoking cessation strategy, with 28.9% abstinence rates compared to 23.4% with nicotine patch alone 1, so maintaining this therapy if possible is beneficial.
• If loose motions persist despite management of bupropion, consider other potential causes or drug interactions 2.

Monitoring for Other Adverse Effects

• While addressing the gastrointestinal symptoms, monitor for other potential adverse effects of bupropion, including:
  • Neuropsychiatric effects such as agitation, depression, or suicidal ideation 1.
  • Seizures, which occur at a rate of approximately 1/1000, particularly in those with risk factors 1, 5.
  • Cardiovascular effects including tachycardia or blood pressure changes 1, 2.