Practical information on using quinolones
Quinolones should generally be reserved for treatment of infections resistant to other drugs or when alternative antibiotics are contraindicated. Resistance to quinolones is now widespread, particularly in Enterobacterales (enteric gram-negative bacilli), Pseudomonas aeruginosa, Campylobacter species and Neisseria gonorrhoeae.
Ciprofloxacin has a broad spectrum of activity, which includes activity against aerobic gram-negative bacteria (including Haemophilus influenzae, Enterobacterales [enteric gram-negative bacilli], P. aeruginosa and gram-negative cocci) and some aerobic gram-positive cocci. It is also active against intracellular bacteria, including Legionella species and some mycobacteria. Ciprofloxacin has poor activity against anaerobic bacteria and streptococci.
Moxifloxacin, an extended-spectrum quinolone, has increased activity against gram-positive aerobic bacteria (including staphylococci and streptococci) compared to ciprofloxacin. Susceptibility among strains of methicillin-resistant Staphylococcus aureus (MRSA) is variable. Moxifloxacin is active against many gram-negative aerobic bacteria, but has poor activity against P. aeruginosa. Moxifloxacin has good activity against anaerobic bacteria and most atypical bacteria that cause pneumonia. It is also used for the management of some mycobacterial infections.
Norfloxacin is reserved mainly for multidrug-resistant cystitis, provided the pathogen is susceptible, and acute infectious diarrhoea (eg traveller’s diarrhoea, cholera).
Ofloxacin is used topically to treat eye infections.
Quinolones are not licensed for use in children on the basis of animal studies that showed an adverse effect on cartilage development with quinolone use; however, available clinical trial data suggest that adverse musculoskeletal events are usually mild and short-term, similar to those observed in adultsBradley, 2014Noel, 2007. Quinolones can be used in children when it is the drug of choice.
Some studies suggest patients using quinolones are at increased risk of aortic aneurysm and dissection1Chen, 2022. Where there are limited other options, quinolones may be used in patients with:
- pre-existing aortic aneurysm or dissection
- a family history of aneurysm
- other risk factors or conditions predisposing for aortic aneurysm and dissection (eg giant cell arteritis, Behcet disease, hypertension, known atherosclerosis).
Quinolones are also associated with rare, disabling adverse effects that mainly affect muscles, tendons, bones and the nervous system23.
Quinolones have many clinically significant drug interactions. Consult an appropriate resource on drug interactions if starting or stopping quinolones in patients taking other drugs.
Quinolones can prolong the QT interval. For more information on drugs that prolong the QT interval, see the CredibleMeds website.
For information on monitoring quinolone plasma concentrations, see Monitoring quinolone blood concentrations.