Which of the following is/are FDA-approved labeled indication(s) for Sulfamethoxazole with Trimethoprim?

A. Upper respiratory tract infections are frequently viral in origin, rendering this sulfonamide combination ineffective. While it covers some respiratory pathogens, it is not a primary labeled indication for general upper respiratory infections. Clinical use is typically reserved for specific bacterial complications. B. Constipation associated with opioid use results from activation of mu-opioid receptors in the gastrointestinal tract. This antimicrobial agent lacks any pharmacological activity on enteric motility or opioid receptors. It is exclusively an anti-infective and has no role in managing bowel dysfunction. C. Urinary tract infections are a primary labeled indication for this synergistic combination. Sulfamethoxazole inhibits dihydropteroate synthase, while trimethoprim inhibits dihydrofolate reductase. This sequential blockade of folic acid synthesis provides potent bactericidal activity against common uropathogens like Escherichia coli. D. Headache symptoms from a common cold are typically managed with analgesics such as acetaminophen or nonsteroidal anti-inflammatory drugs. Sulfamethoxazole with trimethoprim does not possess analgesic or antipyretic properties. It is not indicated for the symptomatic relief of viral upper respiratory syndromes.