Giardiasis and Bupropion-Associated Gastrointestinal Symptoms in a Returning Traveler: A Diagnostic Challenge Case...

Background and Clinical Significance:Giardia lamblia is a protozoan parasite that causes giardiasis, a gastrointestinal disease. The disease commonly manifests with abdominal pain, diarrhea, and emesis. Many giardia infections, however, are asymptomatic and can be easily spread to others. Bupropion, a norepinephrine and dopamine reuptake inhibitor, can have side effects of nausea and abdominal pain, which can mimic or overlap with symptoms of a Giardia lamblia infection. Case Presentation: We present a 39-year-old man who has sex with men (MSM) who presented with abdominal pain with nausea and vomiting. His symptoms began 3 months after returning from a trip to Peru and 1 month after starting bupropion. Bupropion was discontinued upon admission due to suspicion of medication-induced adverse effects. CT imaging revealed thickening of the transverse colon, suggestive of an infectious or inflammatory etiology. The patient's GI-PCR returned positive for Giardia lamblia, and the patient was treated with metronidazole. While the temporal relationship suggests an association, it remains unclear whether the clinical presentation was primarily driven by bupropion, the Giardia infection, or a synergistic effect of both. A norovirus result was indeterminate, and the patient improved after bupropion discontinuation but before metronidazole initiation, leaving open the possibility of a self-limited viral gastroenteritis. Conclusions: This case highlights a possible association between bupropion initiation and the temporal association between bupropion initiation and the detection of symptomatic giardiasis in an MSM patient. Clinicians may consider stool testing for Giardia before attributing gastrointestinal symptoms solely to medication effects. Giardia lamblia should be considered in the differential diagnosis of gastrointestinal symptoms for MSM patients, particularly when compatible exposure history, travel history, or enteric infection risk factors are present.