Antibiotic	Dosage	Effectiveness (%)	Resistance rate (%)*	Cautions and contraindications	Adverse effects	Cost†	U.S. Food and Drug Administration pregnancy category	Comments	Infectious Diseases Society of America recommendation
First-line agents
Fosfomycin (Monurol)	3-g packet one time	91	Up to 0.6	Hypersensitivity to fosfomycin, suspected pyelonephritis	Diarrhea, headache, nausea, vaginitis	NA ($69)	B	Minimal change in gut flora; effective against methicillin-resistant Staphylococcus aureus, ESBL-producing organisms, Enterococcus faecalis, vancomycin-resistant Enterococcus	Single dose is appropriate for acute cystitis despite concerns about effectiveness
Nitrofurantoin	100 mg two times per day for five days	93	Up to 1.6	Glomerular filtration rate less than 40 to 60 mL per minute, history of cholestatic jaundice or hepatic dysfunction with previous use, pregnancy (greater than 38 weeks' gestation), pulmonary or hepatic fibrosis, suspected pyelonephritis; use with caution in patients with G6PD deficiency	Flatus, headache, hemolytic anemia, nausea, neuropathy; risk of pulmonary and hepatic fibrosis with long-term use	$19 (NA)	B	Minimal change in gut flora; should be taken with meals; may turn urine orange; effective against E. faecalis, S. aureus, and Staphylococcus saprophyticus	Five-day course is as effective as three-day course of trimethoprim/ sulfamethoxazole for treatment of acute cystitis
Trimethoprim/ sulfamethoxazole	160/800 mg two times per day for three days	93	Up to 24.2	History of drug-induced thrombocytopenia or other hematologic disorder, local resistance rates greater than 20%, pregnancy, sulfa allergy, use in previous three to six months; use with caution in patients with hepatic or renal impairment, porphyria, or G6PD deficiency	Bone marrow suppression, electrolyte abnormalities, hepatotoxicity, nausea, nephrotoxicity, photosensitivity, rash, Stevens-Johnson syndrome	$4 (NA)	D	Alters gut flora	Three-day course is appropriate if local resistance rates do not exceed 20%
Second-line agents
Fluoroquinolones (e.g., ciprofloxacin, levofloxacin [Levaquin])	Ciprofloxacin: 250 mg two times per day for three days Levofloxacin: 250 to 500 mg per day for three days	90	Ciprofloxacin: up to 17 Levofloxacin: up to 6	Concurrent use with medications that prolong QT interval, hypokalemia, hypomagnesemia, local resistance rates greater than 10%, myasthenia gravis, pregnancy; use with caution in patients with renal impairment	Diarrhea, drowsiness, headache, insomnia, nausea, QT interval prolongation, tendon rupture	Ciprofloxacin: $4 (NA) Levofloxacin: $6 ($81 to $93)	C	Alters gut flora; ciprofloxacin is preferred over other fluoroquinolones; limit use to patients with pyelonephritis or resistant cystitis	Three-day course is highly effective for treatment of cystitis; reserve for treatment of more severe conditions (e.g., pyelonephritis)
Alternative agents if first- and second-line agents are contraindicated
Beta-lactams (e.g., amoxicillin/clavulanate [Augmentin], cefaclor, cefdinir, cefpodoxime, cephalexin [Keflex])	Amoxicillin/clavulanate: 500/125 mg two times per day for three days Cefaclor: 250 mg three times per day for five days Cefdinir: 300 mg two times per day for five days Cefpodoxime: 100 mg two times per day for three days Cephalexin: 500 mg two times per day for seven days	89	Varies by medication	Cephalosporin or penicillin allergy, history of cholestatic jaundice with previous use; use with caution in patients with renal or hepatic impairment, history of infectious colitis, or active mononucleosis; use cephalexin with caution in patients with elevated international normalized ratios	Diarrhea (including Clostridium difficile colitis), headache, hepatotoxicity, nausea, rash, vaginitis	Amoxicillin/clavulanate: $10 ($300) Cefaclor: $28 (NA) Cefdinir: $19 (NA) Cefpodoxime: $21 (NA) Cephalexin: $4 ($130)	B	Alters gut flora; use with caution because of increasing prevalence of ESBL-producing Escherichia coli	Courses of three to seven days are appropriate if other agents cannot be used; fewer supporting data for cephalexin; high resistance rates should preclude use of amoxicillin