50 mg, tablet, human medicine
Assessed clinical scopeCat · Culture-confirmed susceptible lower bacterial cystitis when preferred veterinary-authorised antimicrobials are unsuitable; never pyelonephritis, prostatitis or systemic infection · By mouth
Care settingVeterinarian-directed home treatment after urinalysis and culture, with exact-weight dosing every 8 hours, renal review and early clinical reassessment.
vetman score
3.9/10
Poor / unconvincing
Evidence confidence: Low
Georgia: Discontinued · № რ-042450 · Verified on 22 Oct 2026
Off-label use
A weak-to-poor feline reserve presentation. Consensus and isolate data suggest urinary activity, but direct feline efficacy is sparse, polyneuropathy has now been reported, renal function is critical and these 50/100 mg whole-tablet units cannot deliver a typical cat dose accurately.
Regulatory and scientific credibility4.5/10
The exact Irbit 50 mg plain tablet has identifiable official manufacturer information and a current Georgian registration entry, but another catalogue evidence row says that certificate is suspended for absent GMP documentation. Exact EU/EEA, GB and US entries were not found, and animal use is off-label.
Clinical efficacy4.5/10
ISCAID includes the same 4.4-5 mg/kg every-8-hour reserve regimen for dogs and cats, and canine/feline isolate MICs support potential urinary activity. Direct feline PK and controlled clinical-outcome evidence are essentially absent, bacterial cystitis is uncommon in younger cats and this exact human tablet has no feline formulation evidence.
Safety and tolerability3.5/10
A 2025 cat developed presumptive peripheral polyneuropathy after 4 mg/kg every 8 hours, improving after withdrawal; the case also had impaired renal indicators. Alongside gastrointestinal, hepatic, pulmonary and hypersensitivity risks, sparse feline safety data and renal dependence make the margin materially uncertain.
Clinical practicality2.5/10
A typical 4 kg cat requires about 17.6-20 mg per dose, still well below one 50 mg tablet. The exact plain tablet has no validated equal subdivision or crushing method; although less mismatched than 100 mg, accurate every-8-hour home dosing generally requires an appropriate compounded or alternative presentation.
Full-course cost-effectiveness-
Current comparable full-course local prices were not verified.
Important safety and use flags
- Confirm bacterial cystitis before treatment. Culture and susceptibility are required in cats and strongly preferred in dogs; most feline lower urinary signs are not bacterial, and asymptomatic bacteriuria usually should not be treated.
- Reserve nitrofurantoin for a susceptible lower urinary isolate when preferred veterinary-authorised options are unsuitable. Do not use it as routine empirical therapy or merely because a urine dipstick is abnormal.
- LOWER URINARY TRACT ONLY. Do not use for pyelonephritis, prostatitis, fever/systemic infection or another tissue infection: therapeutic concentrations are achieved in urine, not renal parenchyma, prostate, blood or other tissues.
- Do not use with impaired renal function or inadequate urine production. Reduced excretion can lower urinary efficacy while increasing systemic accumulation and polyneuropathy risk; assess creatinine, hydration and urine output before dosing.
- Stop promptly and reassess for weakness, crouched gait, reduced reflexes, ataxia, tremor, confusion or another neurologic change. Peripheral polyneuropathy can be serious and has been reported in a cat at a conventional q8h regimen.
- Give with food and water and monitor for nausea, vomiting, diarrhoea or anorexia. Stop and investigate persistent gastrointestinal signs, jaundice/hepatopathy, respiratory signs, fever, rash, facial swelling or another hypersensitivity reaction.
- Safety in pregnancy, lactation, breeding animals and very young patients is not adequately established for these exact human presentations. Do not assume human paediatric use proves veterinary reproductive or neonatal safety.
- Review the complete medication list. Antacids containing magnesium, urinary alkalinisers and agents that inhibit tubular secretion can reduce urinary activity or increase toxicity; avoid unreviewed combination with fluoroquinolones because antagonism is described in exact human instructions.
- Dose from exact body weight and the prescribed 4.4-5 mg/kg every-8-hour regimen; do not substitute a once-daily prophylaxis protocol for active infection. Missed q8h doses and poor adherence can materially compromise this short-half-life urinary drug.
- Use only a validated dose unit. These exact 50 mg and 100 mg plain tablets have no documented equal-dose score or validated crushing/powder-division method; do not estimate small fractions by eye. Use an appropriate strength or compounded preparation when the intact tablet cannot match the calculated dose.
Assessment sources+