The daily educational pearl – Antibiotic therapy for UTIs

Current therapeutic guidelines for the management of UTIs in adults

First of all, just as a reminder, if you send the urine off for M/C/S for patients who are discharged home, please document under clinical comments in EDIS what antibiotic you prescribed so that we don’t have to recall the notes every time there is a positive urine culture.

Please note that amoxycillin (without clavulanate) is only recommended if susceptibility of the organism is proven and gentamicin + cephazolin is not appropriate treatment for pyelonephritis.

ACUTE CYSTITIS

Nonpregnant women

trimethoprim 300 mg orally, daily for 3 days
OR
cephalexin 500 mg orally, 12-hourly for 5 days
OR
amoxycillin+clavulanate 500+125 mg orally, 12-hourly for 5 days
OR
nitrofurantoin 100 mg orally, 12-hourly for 5 days

If resistance to all the above drugs is proven and if susceptible: norfloxacin 400 mg orally, 12-hourly for 3 days


Pregnant women (empirical therapy, while awaiting culture results)

cephalexin 500 mg orally, 12-hourly for 5 days (TGA pregnancy category A)
OR
nitrofurantoin 100 mg orally, 12-hourly for 5 days (TGA pregnancy category A)
OR
amoxycillin+clavulanate 500+125 mg orally, 12-hourly for 5 days (TGA pregnancy category B1).

Men (empirical therapy, while awaiting results of investigations)

trimethoprim 300 mg orally, daily for 14 days
OR
cephalexin 500 mg orally, 12-hourly for 14 days
OR
amoxycillin+clavulanate 500+125 mg orally, 12-hourly for 14 days

ACUTE PYELONEPHRITIS

Mild infection in adults (low-grade fever, no nausea or vomiting) may be treated by oral therapy alone (empirical therapy, while awaiting culture results)

amoxycillin+clavulanate 875+125 mg orally, 12-hourly for 10 days
OR
cephalexin 500 mg orally, 6-hourly for 10 days
OR
trimethoprim 300 mg orally, daily for 10 days

If resistance to all the above drugs is proven or the causative organism is Pseudomonas aeruginosa:

norfloxacin 400 mg orally, 12-hourly for 10 days
OR
ciprofloxacin 500 mg orally, 12-hourly for 10 days

Severe infection in adults (empirical therapy, while awaiting culture results)

gentamicin 4 – 6 mg/kg max 480 mg IV, for 1 dose, then determine dosing interval for a maximum of either 1 or 2 further doses based on renal function
PLUS
amoxy/ampicillin 2 g IV, 6-hourly

In patients hypersensitive to penicillin, gentamicin alone will usually suffice.

If gentamicin is contraindicated (see below), as a single drug, use:

ceftriaxone 1 g IV, daily
OR
cefotaxime 1 g IV, 8-hourly

These regimens do not provide adequate cover for P. aeruginosa or enterococci – if highly suspected, contact Microbiology for further advice.

This is (hopefully) not relevant for ED, but:
– subsequent treatment should be guided by susceptibility results and clinical response, with early conversion to oral therapy
– other than for short-term empirical use, gentamicin is no longer recommended except for directed therapy in specific circumstances (after discussion with Microbiology)
– if susceptibility results are not available by 72 hours and empirical IV therapy is still required, cease the gentamicin-containing regimen and use ceftriaxone or cefotaxime as above
– the total duration of therapy is usually 10 to 14 days, but may need to be extended to 21 days in patients with delayed response

Contraindications to aminoglycoside use:

– previous vestibular or auditory toxicity due to an aminoglycoside
– serious hypersensitivity reaction to an aminoglycoside (rare)

Precautions to aminoglycoside use (avoid unless there is no appropriate safer alternative)
– pregnancy (TGA category D)
– pre-existing significant hearing problems, either conductive or sensorineural in origin
– pre-existing vestibular problems (including dizziness, vertigo or tinnitus)
– neuromuscular disorders (including myasthenia gravis, parkinsonism)
– chronic liver disease, severe cholestasis (serum bilirubin greater than 90 micromol/L)
– chronic renal failure or deteriorating renal function – serum creatinine should be checked and creatinine clearance calculated before commencing an aminoglycoside

Aminoglycoside- induced ototoxicity
Patients should be informed, where possible, that there is a chance of balance or hearing problems related to aminoglycoside use, especially if treatment is prolonged. Patients should be regularly asked about any hearing or balance problems and told to report immediately if they occur. For prolonged aminoglycoside courses (greater than 5 days), formal vestibular function testing and high-frequency audiometric testing should be considered if available.

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