Contraindications for Fluoroquinolones
Fluoroquinolones are contraindicated in patients with a history of hypersensitivity to fluoroquinolones, tendon disorders related to previous quinolone use, pregnancy, children/growing adolescents (except in specific circumstances), and patients with certain cardiac conditions that predispose to QT interval prolongation. 1
Absolute Contraindications
- Hypersensitivity reactions: Previous allergic reactions to any fluoroquinolone (class effect) 1
- Pregnancy: Should be avoided due to teratogenic effects shown in animal studies 1
- Breast feeding: Avoid as fluoroquinolones are present in milk in animal studies 1
- Tendon disorders: History of tendon damage or rupture related to previous quinolone use 1
- Congenital or documented QT prolongation: Due to risk of potentially fatal cardiac arrhythmias 1
- Concurrent use with other QT-prolonging medications: Increases risk of cardiac arrhythmias 1
Relative Contraindications (Use with Caution)
- Children and adolescents: Generally contraindicated due to risk of arthropathy in weight-bearing joints, though exceptions exist for specific infections 1
- Elderly patients over 60 years: Higher risk of tendon inflammation and rupture 1, 2
- Patients on corticosteroids: Increased risk of tendon disorders 1, 2
- Renal disease: Dosage adjustment required for most fluoroquinolones; contraindicated in severe renal insufficiency without dose adjustment 1
- Severe liver disease: Particularly Child-Pugh severity score C or transaminase levels five times greater than normal 1
- Seizure disorders or CNS conditions: May lower seizure threshold 1
- Myasthenia gravis: Risk of exacerbation 1
- G6PD deficiency: Risk of hemolytic reactions 1
- Uncorrected hypokalemia or hypomagnesemia: Increases risk of QT prolongation 1, 2
Special Considerations in Pediatric Patients
Fluoroquinolones should be used in children only in specific circumstances after careful risk-benefit assessment 1:
- Appropriate pediatric indications:
- Exposure to aerosolized Bacillus anthracis 1
- Complicated urinary tract infections caused by multidrug-resistant Gram-negative bacteria 1, 3
- Chronic suppurative otitis media or malignant otitis externa caused by P. aeruginosa 1
- Chronic/acute osteomyelitis caused by P. aeruginosa 1
- Pulmonary exacerbations in cystic fibrosis patients with P. aeruginosa 1
- Mycobacterial infections susceptible to fluoroquinolones 1
- Gram-negative infections in immunocompromised hosts with resistance to alternative agents 1
- Multidrug-resistant gastrointestinal infections 1
- Life-threatening allergy to alternative agents 1
Cardiac Contraindications
- Clinically relevant bradycardia 1
- Clinically relevant heart failure with reduced ejection fraction 1
- History of symptomatic arrhythmias 1
- Electrolyte disturbances, particularly uncorrected hypokalemia 1
Monitoring Requirements When Use Is Necessary
- ECG monitoring: Baseline, 2 weeks after starting therapy, and after adding any new medication known to prolong QT interval 1
- Blood glucose: Regular monitoring in patients with diabetes (risk of hypoglycemia) 1
- Routine laboratory monitoring: FBC, U&Es, LFTs should be performed intermittently throughout treatment 1
- Hepatic enzymes and thyroid function: Baseline and periodic monitoring 1
Common Pitfalls to Avoid
- Failure to adjust dosage in renal impairment: Most fluoroquinolones require dose adjustment with creatinine clearance <50 ml/minute 1
- Drug interactions with divalent cations: Antacids containing magnesium or aluminum markedly decrease fluoroquinolone absorption; must separate administration by at least 2 hours 1
- Overlooking tendon risk in elderly: Tendinitis and rupture can occur up to several months after treatment, especially in patients over 60 years 2
- Inappropriate use in uncomplicated infections: Leads to increased bacterial resistance; should be reserved for situations where no safe and effective alternatives exist 1
- Overlooking QT prolongation risk: Particularly important when combining with other QT-prolonging medications 1, 4