PharmacologyTier 1Medical Sciences concept

Antibiotic class-specific adverse effects (fluoroquinolone tendinopathy, nitrofurantoin pulmonary fibrosis)

Core concept

Certain antibiotic classes have a signature adverse effect distinct from generic allergy/GI upset -- matching class to effect is the exam task
Fluoroquinolones: tendinopathy/rupture, QT prolongation, aortic aneurysm/dissection risk
Nitrofurantoin: pulmonary fibrosis (chronic), acute pneumonitis, peripheral neuropathy

Class	Signature effect	Notes
Fluoroquinolones (ciprofloxacin, moxifloxacin)	Tendinopathy/Achilles rupture	Risk inc with age >60, concurrent corticosteroids, renal impairment, transplant
	QT prolongation	Caution with other QT-prolonging drugs
	Aortic aneurysm/dissection	Avoid in known aneurysm/high-risk vascular disease
Nitrofurantoin	Chronic pulmonary fibrosis (long-term prophylactic use)	Also acute hypersensitivity pneumonitis (early)
	Peripheral neuropathy	Caution in renal impairment (accumulation, also reduced urinary efficacy)
Aminoglycosides	Nephrotoxicity + ototoxicity (cochlear and vestibular)	Requires TDM
Linezolid	Serotonin syndrome (weak MAOI), thrombocytopenia (long courses)
Chloramphenicol	Aplastic anaemia (idiosyncratic), grey baby syndrome

Fluoroquinolone + corticosteroid = major risk factor for tendon rupture -- avoid combination where possible, especially in the elderly
Nitrofurantoin contraindicated at eGFR <30-45 (varies by guideline) -- reduced urinary concentration (loses efficacy) and accumulates systemically (inc toxicity)
Long-term nitrofurantoin prophylaxis (recurrent UTI) needs periodic review for insidious dyspnoea/cough -- pulmonary fibrosis can be irreversible if missed

QT prolongation risk shared with macrolides -- additive when combined
Nitrofurantoin avoided near term in pregnancy (theoretical neonatal haemolysis in G6PD deficiency) -- separate mechanism from pulmonary fibrosis
Tendinopathy risk factors overlap with those for corticosteroid-induced tendon weakening independently

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