What are the contraindications for antibiotics (abx)?

Contraindications for Antibiotics

Antibiotics are absolutely contraindicated in patients with known hypersensitivity to the specific drug class, during pregnancy for certain agents (streptomycin, fluoroquinolones, doxycycline), and in specific disease states including myasthenia gravis for aminoglycosides and certain macrolides. 1, 2, 3

Absolute Contraindications by Drug Class

Aminoglycosides (Streptomycin, Amikacin, Kanamycin, Gentamicin)

• Pregnancy: Streptomycin is absolutely contraindicated due to risk of irreversible fetal hearing loss and ototoxicity 1
• Myasthenia gravis: All aminoglycosides are contraindicated due to impaired neuromuscular transmission and risk of neuromuscular blockade 2, 3
• Known hypersensitivity to any aminoglycoside 1

Fluoroquinolones (Levofloxacin, Moxifloxacin, Gatifloxacin)

• Pregnancy and lactation: Should be avoided due to teratogenic effects 1
• Children under 8-12 years: Not approved for long-term use due to effects on bone and cartilage growth, though may be considered for multidrug-resistant tuberculosis 1
• Myasthenia gravis: Use with extreme caution as they can decrease neuromuscular transmission 2

Macrolides (Clarithromycin, Azithromycin, Erythromycin)

Clarithromycin-specific contraindications 4:

• Known hypersensitivity to clarithromycin, erythromycin, or any macrolide
• History of cholestatic jaundice or hepatic dysfunction with prior clarithromycin use
• Concomitant use with cisapride or pimozide (risk of fatal cardiac arrhythmias)
• Concomitant use with colchicine in patients with renal or hepatic impairment
• Concomitant use with lomitapide, lovastatin, or simvastatin
• Concomitant use with ergot alkaloids or lurasidone
• QT prolongation, ventricular arrhythmias, or torsades de pointes history

Azithromycin in myasthenia gravis: Listed under cautions rather than absolute contraindications, but carries significant risk of worsening myasthenic symptoms 3

Tetracyclines (Doxycycline)

• Children under 8 years: Risk of permanent teeth discoloration and enamel hypoplasia 5
• Pregnancy and nursing women: Contraindicated 5
• Myasthenia gravis: May cause exacerbation due to weak neuromuscular blockade 5

Vancomycin

• Known hypersensitivity to vancomycin is the only absolute contraindication 6
• Safe in myasthenia gravis: Does not impair neuromuscular transmission 2
• Avoid combination with aminoglycosides in myasthenia gravis patients due to increased nephrotoxicity risk 2

Clinical Situations Where Antibiotics Are Contraindicated

Viral Infections

• Acute bronchitis without pneumonia: Do not initiate antibiotic therapy 1
• Common cold: Antibiotics should never be prescribed 1
• Pharyngitis without confirmed Group A Streptococcus: Only treat with antibiotics after positive rapid antigen test or culture 1
• Acute laryngitis/dysphonia: Do not routinely prescribe antibiotics as most cases are viral and self-limited within 7-10 days 1

Acute Rhinosinusitis

• Symptoms less than 10 days: Reserve antibiotics only for persistent symptoms >10 days, severe symptoms with high fever (>39°C) and purulent discharge for ≥3 consecutive days, or "double sickening" pattern 1

Organ-Specific Contraindications and Cautions

Hepatic Disease

• Ethionamide and ionamide: Use with caution; requires baseline and monthly liver function monitoring 1
• Clarithromycin: Contraindicated if history of cholestatic jaundice or hepatic dysfunction with prior use 4
• Doxycycline: Requires baseline and periodic liver function monitoring; serious hepatotoxicity possible 5

Renal Disease

• Streptomycin: Use with extreme caution; requires dose reduction to 12-15 mg/kg two to three times weekly (not daily) in creatinine clearance <30 mL/min to avoid ototoxicity and nephrotoxicity 1
• Clarithromycin: Reduce dose by 50% if creatinine clearance 30-60 mL/min; reduce by 75% if <30 mL/min when used with atazanavir or ritonavir 4
• Fluoroquinolones: Adjust to 750-1000 mg three times weekly if creatinine clearance <50 mL/min 1

Critical Drug Interactions Constituting Contraindications

With Clarithromycin 4:

• Cisapride, pimozide (fatal arrhythmias)
• Colchicine in renal/hepatic impairment
• Lomitapide (markedly increased transaminases)
• Lovastatin, simvastatin (rhabdomyolysis)
• Ergot alkaloids (ergotism)
• Lurasidone (serious adverse reactions)

With Fluoroquinolones 1:

• Antacids and medications with divalent cations: Must separate administration by at least 2 hours to avoid absorption failure

Common Pitfalls to Avoid

• Do not prescribe antibiotics for fever alone: Investigate the root cause before starting treatment 7
• Do not treat colonization: In absence of clinical infection signs, colonization rarely requires treatment 7
• Avoid empiric broad-spectrum antibiotics in patients without risk factors for multidrug-resistant pathogens 8, 7
• Never use azithromycin as monotherapy for non-tuberculous mycobacterial infections—this creates macrolide resistance 3
• Do not ignore medication timing: Fluoroquinolones taken with antacids will fail therapeutically 1