Nitrofurantoin

What is this medication for?

• Susceptible lower urinary tract infections and prophylaxis against recurrent UTI (E. coli, Klebsiella, Enterobacter, Enterococci, Staph aureus/epidermidis, Citrobacter)
• Pyelonephritis, renal cortical/perinephric abscess, systemic infection — no tissue levels

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Proteus (urease-producing, alkalinizes urine) is doubly protected — intrinsic resistance + pH-driven activity loss.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• stomach/intestinal disturbance (Main effect)
• Peripheral neuropathy, male infertility (Human-class effects)
• Hemolytic low red blood cell counts (GLUT-deficient humans; neonates)

Worth a phone call to your veterinarian

• Hepatopathy (drug-induced) (Rare but documented — check liver enzymes if unwell)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Renal impairment (no urinary concentration achieved + accumulation); hypersensitivity
• has or has had: Not for pyelonephritis/renal infections; G6PD-like hemolysis caution in neonates; pregnancy near term

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Magnesium trisilicate antacids
  • Fluoroquinolones
  • Urinary alkalinizers

Storage and handling

Room temperature; macrocrystal formulations reduce stomach/intestinal upset.

Good to know

• "Bladder-liner, not a systemic antibiotic": brilliant for recurrent sporadic bacterial cystitis prophylaxis (nightly post-void dosing maximizes bladder residence), useless for kidney infection — a favorite exam distinction.
• Prophylaxis is a last step AFTER treating the active infection and hunting for underlying causes (anatomy, stones, incontinence, endocrine).
• Proteus (urease-producing, alkalinizes urine) is doubly protected — intrinsic resistance + pH-driven activity loss.