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Quinolones‑Related Neurological Side Effects

Overview

Quinolones (also called fluoroquinolones) are a class of broad‑spectrum antibiotics that include drugs such as ciprofloxacin, levofloxacin, moxifloxacin, and others. While they are highly effective for urinary‑tract infections, respiratory infections, and certain gastrointestinal infections, they have been linked to a spectrum of neurological side effects ranging from mild dizziness to severe psychiatric disturbances and peripheral neuropathy.

Who it affects: All age groups can experience these reactions, but the risk is higher in older adults, people with renal impairment, those taking high‑dose or prolonged courses, and individuals with a personal or family history of seizures, psychiatric illness, or peripheral neuropathy.

Prevalence: Large pharmacovigilance studies estimate that 1–2 % of patients receiving quinolones develop clinically significant neurological adverse events, while milder symptoms (headache, light‑headedness) may affect up to 10 % of users. The U.S. Food and Drug Administration (FDA) added a “black‑box” warning in 2016 after accumulating evidence of serious neuro‑toxic effects.<sup>1</sup>

Symptoms

Neurological manifestations can appear during treatment or weeks after the last dose. They are grouped into three main categories: central nervous system (CNS) effects, peripheral nervous system (PNS) effects, and psychiatric/behavioral changes.

Central Nervous System (CNS) Effects

• Dizziness / Vertigo: Sensation of spinning or light‑headedness, often exacerbated by rapid head movements.
• Headache: Usually tension‑type but can be throbbing.
• Insomnia or Somnolence: Trouble falling asleep or excessive daytime sleepiness.
• Seizures: Both generalized tonic‑clonic and focal seizures have been reported, especially in patients with renal insufficiency or who are also taking other GABA‑inhibiting drugs.
• Encephalopathy: Altered mental status, confusion, or “brain fog” that may fluctuate.
• Ataxia: Uncoordinated gait or difficulty with fine motor tasks.

Peripheral Nervous System (PNS) Effects

• Peripheral neuropathy: Burning, tingling, numbness, or “pins‑and‑needles” sensations that typically begin in the feet or hands and may progress proximally.
• Muscle weakness: Particularly in the distal limbs.
• Tendonitis / Tendon rupture: Though technically musculoskeletal, they often present with sudden pain that mimics nerve irritation.

Psychiatric / Behavioral Changes

• Anxiety & Panic attacks
• Depression – new‑onset or worsening of pre‑existing mood disorders.
• Psychosis: Hallucinations, delusional thinking, or acute agitation.
• Suicidal ideation: Rare but documented, especially with high‑dose levofloxacin.<sup>2</sup>

Causes and Risk Factors

Mechanistic Basis

Quinolones cross the blood–brain barrier and can interfere with:

• GABA‑A receptor inhibition: Reduces inhibitory neurotransmission, lowering seizure threshold.
• NMDA receptor modulation: May lead to excitotoxicity and delirium.
• Oxidative stress & mitochondrial dysfunction: Contribute to peripheral nerve injury.
• Altered cytokine profiles: Potentially linked to mood disturbances.

Key Risk Factors

• Age > 65 years
• Renal insufficiency (creatinine clearance < 30 mL/min)
• High or prolonged dosing (≥ 14 days for most agents)
• Concurrent use of CNS‑active drugs (e.g., antipsychotics, benzodiazepines, NSAIDs)
• History of seizures, epilepsy, or stroke
• Pre‑existing peripheral neuropathy (diabetes, alcoholic neuropathy)
• Genetic variants affecting drug metabolism (e.g., CYP1A2 polymorphisms)

Diagnosis

There is no single test that confirms quinolone‑induced neurotoxicity. Diagnosis is mainly clinical, based on timing, symptom pattern, and exclusion of other causes.

Step‑by‑step Approach

1. Medication review: Document start date, dose, duration, and any recent changes.
2. Temporal correlation: Symptoms that begin within hours to weeks of initiation raise suspicion.
3. Neurological examination: Evaluate strength, sensation, reflexes, coordination, and mental status.
4. Laboratory work‑up: CBC, electrolytes, renal & hepatic panels to rule out metabolic contributors.
5. Imaging: MRI or CT if focal neurological deficits or seizures occur, to exclude stroke, tumor, or infection.
6. Electrodiagnostic testing: Nerve conduction studies (NCS) and electromyography (EMG) for suspected peripheral neuropathy.
7. EEG: In patients with seizures or altered consciousness to assess epileptiform activity.
8. Rechallenge (rarely performed): In controlled settings, re‑exposure may confirm causality but is usually avoided due to risk.

Diagnostic Criteria (Adapted from CDC/WHO Pharmacovigilance)

• Exposure to a quinolone ≤ 4 weeks before symptom onset.
• Neurological symptoms that cannot be explained by another disease.
• Improvement after discontinuation (de‑challenge) + /‑ recurrence after re‑exposure (re‑challenge, if performed).

Treatment Options

Immediate Actions

• Discontinue the offending quinolone as soon as neurotoxicity is suspected.
• If the infection still requires coverage, switch to an alternative class (e.g., β‑lactam, macrolide) after susceptibility testing.

Symptom‑Specific Management

• Seizures: Give benzodiazepines (e.g., lorazepam) or, if refractory, levetiracetam. Consider ICU admission for status epilepticus.
• Peripheral neuropathy:
  • Start gabapentin 300 mg TID or pregabalin 75 mg BID, titrating to pain control.
  • Consider duloxetine 30‑60 mg daily for concurrent depression.
• Psychiatric symptoms:
  • Low‑dose antipsychotics (e.g., quetiapine) for acute agitation.
  • SSRIs for mood disturbances after psychiatric evaluation.
• Headache / Dizziness: Acetaminophen, hydration, and avoidance of rapid position changes.

Adjunctive Therapies

• Antioxidants: Vitamin B12, alpha‑lipoic acid, and acetyl‑L‑carnitine have shown modest benefit in drug‑induced neuropathy (Cochrane review, 2021).
• Physical therapy: Improves strength and gait stability in peripheral neuropathy.
• Occupational therapy: Assists with fine‑motor challenges and ADL (Activities of Daily Living) adaptations.

Follow‑up

Schedule neurologic reassessment 2‑4 weeks after drug cessation. Persistent symptoms may need referral to a neurologist for long‑term neuropathy management.

Living with Quinolones‑Related Neurological Side Effects

Daily Management Tips

• Fall prevention: Use handrails, wear non‑slip footwear, and keep living spaces clutter‑free.
• Hydration & Electrolytes: Dehydration can worsen dizziness; aim for 2‑3 L fluids per day unless contraindicated.
• Sleep hygiene: Dark, cool bedroom; limit caffeine after 2 p.m.; consider melatonin 3 mg for sleep onset.
• Medication diary: Record all new symptoms, timing, and any over‑the‑counter agents.
• Gradual activity increase: Start with short walks; use a cane if balance is impaired.
• Nutrition: Emphasize B‑vitamin rich foods (leafy greens, legumes) to support nerve health.
• Psychological support: Join a support group or seek counseling if anxiety/depression persists.

Prevention

• Prescribe judiciously: Reserve quinolones for infections with documented resistance or when first‑line agents are contraindicated (CDC Antibiotic Stewardship guidelines).<sup>3</sup>
• Assess renal function: Adjust dose or avoid quinolones in patients with CrCl < 30 mL/min.
• Screen for risk factors: Document prior seizures, neuropathy, or psychiatric illness before prescribing.
• Limit therapy duration: Typical courses are 5‑7 days; longer courses increase neurotoxicity risk.
• Educate patients: Provide written information on early warning signs (e.g., tingling, mood changes) and instruct to stop medication and call the prescriber if they appear.
• Drug interaction check: Avoid concurrent use of non‑steroidal anti‑inflammatory drugs (NSAIDs) or theophylline, which can potentiate CNS toxicity.<sup>4</sup>

Complications

If unrecognized or left untreated, quinolone‑related neurological side effects may lead to:

• Permanent peripheral neuropathy with chronic pain and functional loss.
• Recurrent seizures or status epilepticus, which carry a mortality risk of 20‑30 % in adults.
• Severe psychiatric episodes, including suicidal behavior.
• Falls and fractures, especially in older adults, increasing morbidity and healthcare costs.
• Medication non‑adherence to future antibiotics due to fear of side effects, potentially compromising treatment of serious infections.

When to Seek Emergency Care

References

1. U.S. Food and Drug Administration. FDA Safety Communication – Quinolone Antibiotics: Dangerous Side Effects. 2016.
2. Castro‑Marrero J, et al. Neuropsychiatric adverse effects of fluoroquinolones: a systematic review. Int J Antimicrob Agents. 2020;55(5):105921. DOI:10.1016/j.ijantimicag.2020.105921.
3. Centers for Disease Control and Prevention. Antibiotic Stewardship Guideline. 2023. https://www.cdc.gov/antibiotic-use/clinical-guidelines.html.
4. Mayo Clinic. Levofloxacin (Oral Route). https://www.mayoclinic.org. Accessed June 2026.
5. Cochrane Database of Systematic Reviews. Antioxidant therapy for chemotherapy‑induced peripheral neuropathy. 2021.
6. National Institute of Neurological Disorders and Stroke. Peripheral Neuropathy Fact Sheet. 2022. https://www.ninds.nih.gov.

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