Can Ciprofloxacin Cause Seizures? Understanding the Risk and Neurotoxicity

October 12, 2025 •

4 min read

While considered rare, seizures are a known, serious adverse effect of the fluoroquinolone antibiotic ciprofloxacin, with cases reported in both predisposed and otherwise healthy individuals. Patients with certain underlying conditions are at a significantly higher risk of developing these central nervous system complications.

Quick Summary

Ciprofloxacin, a fluoroquinolone antibiotic, can cause seizures, though this is a rare side effect. The risk is higher for individuals with predisposing factors such as kidney issues, older age, or pre-existing CNS disorders.

Key Points

Rare but Serious Risk: Ciprofloxacin can cause seizures, though this is an uncommon to rare adverse effect.
GABA Interference: The mechanism is thought to involve ciprofloxacin's interference with GABA, the brain's primary inhibitory neurotransmitter, increasing neuronal excitability.
High-Risk Patient Groups: Individuals with existing CNS disorders (e.g., epilepsy), kidney problems, or advanced age face a significantly higher risk.
Drug Interactions: Concomitant use with other medications, like theophylline, can dramatically increase the risk of seizures and other severe reactions.
Early Symptom Recognition: Seizures are the most severe symptom, but precursors can include dizziness, confusion, tremors, or psychological disturbances.
Immediate Medical Attention: If a seizure or other signs of neurotoxicity occur, the medication should be stopped immediately, and a doctor should be notified.
FDA Warning: The FDA includes a boxed warning for ciprofloxacin and other fluoroquinolones regarding serious CNS adverse effects.

Ciprofloxacin and the Central Nervous System

Ciprofloxacin is a widely prescribed antibiotic from the fluoroquinolone class, used to treat a variety of bacterial infections. While generally effective, it, like other drugs in its class, carries a risk of adverse effects on the central nervous system (CNS). Seizures are one of the most severe manifestations of this neurotoxicity, and the U.S. Food and Drug Administration (FDA) includes a warning about CNS effects, including seizures, in the drug's prescribing information.

The Neurotoxic Mechanism of Ciprofloxacin

The precise way ciprofloxacin induces neurotoxicity is not fully understood, but the primary proposed mechanism involves interference with neurotransmitter systems. The excitatory effects that can lead to seizures are thought to be related to the drug's ability to cross the blood-brain barrier and inhibit the binding of gamma-aminobutyric acid (GABA) to its receptors. GABA is the main inhibitory neurotransmitter in the brain, and by blocking its action, ciprofloxacin reduces the brain's natural inhibitory signals. This can increase neuronal excitability, lower the seizure threshold, and potentially trigger a seizure. Some research also suggests a role in the activation of excitatory N-methyl-D-aspartate (NMDA) receptors.

Key Risk Factors for Ciprofloxacin-Induced Seizures

Not all patients taking ciprofloxacin are at an equal risk of developing seizures. A number of factors have been identified that significantly increase a person's susceptibility to this adverse effect. Healthcare providers should carefully evaluate these risk factors before prescribing the medication.

Key risk factors include:

Pre-existing CNS disorders: Individuals with a history of epilepsy, stroke, cerebral arteriosclerosis, brain tumors, or head trauma are at a higher risk.
Renal Insufficiency: Impaired kidney function can lead to higher-than-normal concentrations of ciprofloxacin in the body and brain, increasing the likelihood of toxicity.
Advanced Age: Elderly patients are generally more susceptible to drug-induced neurotoxicity due to altered drug metabolism and potential co-morbidities.
Concurrent Drug Interactions: Combining ciprofloxacin with other drugs that lower the seizure threshold can increase the risk. A well-documented interaction is with theophylline, a medication for respiratory conditions, where serious and fatal reactions have occurred. Nonsteroidal anti-inflammatory drugs (NSAIDs) may also enhance the neurotoxic effects of fluoroquinolones.
Electrolyte Abnormalities: Severe electrolyte imbalances, such as hypo- or hyperglycemia, can contribute to seizures.
Thyrotoxicosis: An overactive thyroid condition has been identified in case studies as a potential predisposing factor.
Dosage: High doses of ciprofloxacin can increase the risk of adverse neurological events.

Clinical Manifestations of Ciprofloxacin Neurotoxicity

Seizures are the most severe neurological complication, but ciprofloxacin can cause a range of other CNS disturbances. Recognizing these symptoms early is crucial. Patients and caregivers should be aware of the following potential signs of neurotoxicity:

Dizziness and lightheadedness
Headaches
Sleep disturbances, including insomnia and nightmares
Confusion, disorientation, or memory problems
Hallucinations (seeing or hearing things that are not there)
Tremors or restlessness
Psychotic reactions or depression
Anxiety or nervousness

If any of these symptoms occur, especially in conjunction with risk factors, the medication should be discontinued and a healthcare provider contacted immediately.

Comparing Neurotoxic Potential Among Fluoroquinolones

While all fluoroquinolones carry a risk of neurotoxicity, their propensity for causing adverse CNS effects can vary. The FDA's boxed warning applies to the entire class due to the potential for disabling and irreversible side effects. The following table provides a general comparison based on reported clinical experience, though individual risk can vary widely based on patient factors.


Fluoroquinolone	Associated Neurotoxic Effects (Frequency)	Proposed Mechanism	Notable Risk Factors	Notes
Ciprofloxacin	Seizures (uncommon to rare), confusion, dizziness, psychosis, tremors	GABA-A receptor antagonism, NMDA receptor activation	Renal dysfunction, older age, CNS pathology, concomitant theophylline	One of the most studied for neurotoxicity; CNS penetration may be lower than some others.
Levofloxacin	Seizures (rare), delirium with psychotic features, dizziness, insomnia	GABA-A receptor antagonism, NMDA receptor activation	Renal dysfunction, older age, CNS pathology	The active L-isomer of ofloxacin, reports of delirium and seizures.
Ofloxacin	Dizziness, headache, insomnia; fewer neurotoxicity cases reported than ciprofloxacin	GABA-A receptor antagonism	Renal dysfunction, extremes of age	Has higher CNS permeability than ciprofloxacin but fewer neurotoxic reports, suggesting a complex relationship between penetration and toxicity.

Management and Prevention

For patients deemed at risk, healthcare providers may need to adjust the ciprofloxacin dose, especially in cases of renal impairment. Close monitoring of elderly patients and those with underlying CNS disorders is crucial. If neurotoxic symptoms, such as dizziness, confusion, or seizures, arise, the primary course of action is to stop the ciprofloxacin immediately. In the event of a seizure, symptomatic treatment and appropriate care should be instituted. In severe cases, the possibility of other causes of seizures must also be ruled out. Awareness of potential drug-drug interactions, particularly with theophylline, is essential for prevention.

Conclusion

While ciprofloxacin is an effective and important antibiotic, its potential to cause serious neurological side effects, including seizures, is a significant consideration, especially for vulnerable populations. The risk is low but serious and appears to be exacerbated by factors such as renal impairment, advanced age, and pre-existing CNS pathology. The mechanism is thought to involve antagonism of inhibitory GABA receptors within the central nervous system. Patients must be aware of potential symptoms and seek immediate medical attention if they experience any signs of neurotoxicity. By recognizing the risks and monitoring patients appropriately, healthcare professionals can mitigate the dangers associated with this powerful medication. For more detailed prescribing information and risk warnings, refer to the official FDA Drug Labeling for Ciprofloxacin.

Frequently Asked Questions

Seizures from ciprofloxacin are uncommon to rare. In a study of hospitalized patients, the incidence was reported as approximately 0.06%, though it is more common in individuals with predisposing risk factors.

Ciprofloxacin can lower the seizure threshold by interfering with the brain's neurotransmitter systems. It is known to inhibit GABA-A receptors, which normally suppress neuronal activity, thereby increasing overall brain excitability.

Risk factors include a history of seizures or other CNS disorders, renal impairment, older age, high drug dosage, co-administration with other neurotoxic drugs (like theophylline), and electrolyte imbalances.

While systemic absorption is minimal with eye drops, there are case reports of seizures linked to the use of ciprofloxacin eye drops, suggesting that some absorption can occur and cause systemic effects in sensitive individuals.

If you experience any signs of a seizure or serious CNS effects like tremors or confusion, you should stop taking ciprofloxacin immediately and contact a healthcare professional for guidance.

Most neurological adverse effects, including seizures, resolve after discontinuing the medication. However, severe reactions can occur, and it is crucial to address them promptly to prevent lasting damage.

Yes, the FDA has issued a boxed warning for ciprofloxacin and other fluoroquinolones, highlighting the risk of serious CNS effects, including seizures. The warning advises caution in patients with CNS disorders.

Yes, other antibiotics, including some beta-lactams and polymyxins, have been associated with seizures, particularly in patients with pre-existing risk factors or impaired renal function.