Sulfamethoxazole / Trimethoprim — Sulfonamide + dihydrofolate reductase inhibitor. Study the mechanism, listed uses and warnings from the US label on one sourced card.
Generic name
Sulfamethoxazole / Trimethoprim
Class
Sulfonamide + dihydrofolate reductase inhibitor
Mechanism
Blocks sequential bacterial folate pathways: sulfamethoxazole competes with PABA to inhibit dihydrofolic-acid synthesis, while trimethoprim reversibly inhibits dihydrofolate reductase and tetrahydrofolic-acid production.
Used for
Urinary tract infection due to susceptible organisms; Pediatric acute otitis media due to susceptible organisms when the combination offers an advantage over alternatives; Documented Pneumocystis jirovecii pneumonia, or prevention in selected immunosuppressed people at increased risk
Common side effects
Nausea; Vomiting; Anorexia; Rash
Warnings
Severe skin reactions (SJS/TEN); Contraindicated under 2 months of age; Embryofetal toxicity
Interactions
Warfarin (CYP2C9); Dofetilide (contraindicated); Diuretics in the elderly
Brand questions use only name pairings verified against the linked product source. Unverified pairings are withheld from these questions; the other study content remains available.
Label date: 20260902 · For learning, not clinical decisions. US label and brand information; always consult the current source.
Source snapshot checked: 2026-10-21. The source document and selected fields were compared. The complete card has not had an independent clinical review.
Mechanism: Interferes with bacterial cell-wall formation, killing susceptible organisms while they are actively multiplying.
On both cards: Common side effects — Nausea; Vomiting; Rash
Only on the Amoxicillin card: Used for — Ear, nose and throat infections caused by the specified susceptible beta-lactamase-negative bacteria; Genitourinary infections caused by the specified susceptible beta-lactamase-negative bacteria; Skin and skin-structure infections caused by the specified susceptible beta-lactamase-negative bacteria; Lower respiratory infections caused by the specified susceptible beta-lactamase-negative bacteria · Common side effects — Diarrhea · Warnings — Anaphylactic reactions; Severe cutaneous adverse reactions; C. difficile-associated diarrhea · Interactions — Probenecid; Oral anticoagulants; Allopurinol
Mechanism: Binds the 30S ribosomal subunit and inhibits bacterial protein synthesis; bacteriostatic against Gram-positive and Gram-negative bacteria.
On both cards: Common side effects — Nausea; Vomiting; Anorexia
Only on the Doxycycline card: Used for — Specified rickettsial infections, including Rocky Mountain spotted fever; Respiratory infection caused by Mycoplasma pneumoniae; The specified susceptible chlamydial infections, including lymphogranuloma venereum, trachoma, inclusion conjunctivitis and uncomplicated urethral, endocervical or rectal infection in adults · Common side effects — Diarrhea; Photosensitivity · Warnings — Hypersensitivity to tetracyclines; Tooth discoloration during tooth development; young-child use requires weighing benefits in severe or life-threatening infections; C. difficile-associated diarrhea; Serious skin reactions and intracranial hypertension · Interactions — Anticoagulants; Penicillin; Antacids (Al, Ca, Mg) and iron
Mechanism: Inhibits bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, disrupting processes required for bacterial DNA replication and maintenance.
On both cards: Common side effects — Nausea; Vomiting; Rash
Only on the Ciprofloxacin card: Used for — UTIs due to specified susceptible bacteria in adults, and selected complicated UTI/pyelonephritis in children aged 1–17; acute uncomplicated cystitis use is reserved for patients without alternatives; Specified susceptible lower-respiratory infections in adults; acute chronic-bronchitis exacerbation use is reserved for patients without alternatives; Specified susceptible skin, bone and joint infections in adults; Post-exposure inhalational anthrax and source-specified plague treatment/prevention in adults and children · Common side effects — Diarrhea; Abnormal liver function tests · Warnings — QT prolongation; Hepatotoxicity; C. difficile-associated diarrhea · Interactions — Tizanidine (contraindicated); Theophylline; Other CYP1A2 substrates
An item counts as shared only when both cards use the same wording. If a card does not list an item, that is not a statement that the effect never occurs.
Capsera