Urgent Care For UTI 5 — Questions and Answers
Question 1: A 30-year-old woman with a UTI is prescribed ciprofloxacin. She also takes antacids containing magnesium and aluminum. What counseling should be provided?
- Take ciprofloxacin and antacid together for maximum absorption
- Separate ciprofloxacin and antacids by at least 2 hours to prevent chelation reducing drug absorption (Correct answer)
- Antacids have no interaction with fluoroquinolones
- Switch to a different antibiotic class to avoid any interaction
Correct answer: Separate ciprofloxacin and antacids by at least 2 hours to prevent chelation reducing drug absorption
Divalent and trivalent cations in antacids chelate fluoroquinolones in the GI tract, significantly reducing antibiotic absorption; spacing by 2–6 hours prevents this interaction.
Question 2: A patient with an uncomplicated UTI reports phenazopyridine (AZO) use. What should the patient be counseled about this medication?
- It treats the bacterial infection and can replace antibiotics
- It is an analgesic that relieves dysuria symptoms but has no antibacterial activity (Correct answer)
- It should not be taken with any antibiotic
- It can cure UTIs when taken for 7 days
Correct answer: It is an analgesic that relieves dysuria symptoms but has no antibacterial activity
Phenazopyridine is a urinary tract analgesic that relieves pain and burning but has no antimicrobial activity and does not treat the underlying infection.
Question 3: A 45-year-old woman with a UTI has a creatinine clearance of 28 mL/min. Which antibiotic should be avoided due to risk of drug accumulation and pulmonary toxicity?
- Amoxicillin-clavulanate
- Cephalexin
- Nitrofurantoin (Correct answer)
- Fosfomycin
Correct answer: Nitrofurantoin
Nitrofurantoin is contraindicated when CrCl is below 30 mL/min because impaired renal excretion leads to subtherapeutic urinary levels and systemic accumulation causing pulmonary toxicity.
Question 4: A patient treated for UTI 10 days ago returns with recurrence of symptoms. Repeat culture grows the same E. coli as before. What does this most likely represent?
- Reinfection with a new strain from the environment
- Treatment relapse indicating possible treatment failure or undertreated focus (Correct answer)
- Antibiotic hypersensitivity reaction
- Interstitial cystitis flare triggered by antibiotics
Correct answer: Treatment relapse indicating possible treatment failure or undertreated focus
Recurrence with the same organism within 2 weeks of completing therapy suggests relapse due to inadequate treatment or an occult focus such as renal parenchymal involvement.
Question 5: A 50-year-old woman presents with UTI symptoms. Her UA is positive, but she reports beta-lactam allergy described as a rash. Which antibiotic is safe to prescribe?
- Amoxicillin
- Cephalexin with caution only
- Nitrofurantoin (Correct answer)
- Ampicillin-sulbactam
Correct answer: Nitrofurantoin
Nitrofurantoin is not a beta-lactam and is safe to use in patients with penicillin or cephalosporin allergy.
Question 6: Which of the following best describes the mechanism of action of nitrofurantoin?
- Inhibits bacterial cell wall synthesis by binding penicillin-binding proteins
- Inhibits DNA gyrase and topoisomerase IV
- Disrupts multiple bacterial enzyme systems after intracellular reduction by bacterial enzymes (Correct answer)
- Inhibits dihydropteroate synthase in folate synthesis
Correct answer: Disrupts multiple bacterial enzyme systems after intracellular reduction by bacterial enzymes
Nitrofurantoin is reduced by bacterial enzymes to reactive intermediates that damage bacterial DNA, ribosomes, and other macromolecules through multiple mechanisms.
Question 7: A 29-year-old woman presents to urgent care with classic UTI symptoms. She is not pregnant, has no allergies, and her UA confirms UTI. Local E. coli resistance to TMP-SMX is 25%. Which empiric treatment is most appropriate?
- TMP-SMX DS twice daily for 3 days since it's still worth trying
- Nitrofurantoin macrocrystals 100 mg twice daily for 5 days (Correct answer)
- Ciprofloxacin 500 mg twice daily for 7 days
- Ceftriaxone 1 g IV once in office then oral step-down
Correct answer: Nitrofurantoin macrocrystals 100 mg twice daily for 5 days
When local resistance to TMP-SMX exceeds 20%, IDSA guidelines recommend alternative first-line agents; nitrofurantoin remains an excellent choice with low resistance rates.
Urgent Care For UTI 5
A 30-year-old woman with a UTI is prescribed ciprofloxacin.
She also takes antacids containing magnesium and aluminum.
What counseling should be provided?