Which symptom is a common adverse effect of sulfamethoxazole therapy?

• A. Diarrhea
• B. Rash
• C. Dizziness
• D. Hair loss

Answer: (A)

Diarrhea is the most common adverse effect with sulfamethoxazole therapy because sulfonamides frequently irritate the GI tract and disrupt the normal intestinal flora, leading to loose stools. This antibiotic-associated diarrhea reflects both direct mucosal irritation and microbiome changes from the drug. Rash can occur as a hypersensitivity reaction, but it’s less common than GI upset. Dizziness and hair loss are not typical adverse effects of sulfamethoxazole. If diarrhea is persistent or severe, monitor for dehydration and signs of antibiotic-associated colitis, and seek care if there are alarming symptoms.