Seizure Risk-Factor Checklist

What this checklist is, and what it is not

Clinicians talk about the "seizure threshold" as a shorthand for the brain's balance between excitation and inhibition. Many things can tip that balance toward a seizure: certain medicines, withdrawal from alcohol or sedatives, disturbances of sodium, calcium, magnesium or glucose, fever, sleep loss, and structural or acquired brain disease. When several of these factors coincide, the risk rises in a way that is easy to underestimate, especially in a patient whose medication list has grown one prescription at a time.

The value of the checklist is practical. A busy prescriber adding tramadol for pain, or an on-call doctor seeing a confused patient on cefepime with kidney failure, benefits from a systematic sweep of the factors that are most often missed. The checklist turns that sweep into a routine: tick, total, review, act.

Drugs that lower the seizure threshold

Medicines are the most actionable item on the list, because a drug can usually be changed. The following are the agents most consistently cited in product labels and drug-interaction references. Where a verified incidence figure exists, it is given; where none is published, the factor is described qualitatively rather than with an invented number.

Bupropion

Bupropion lowers the seizure threshold in a dose-related way, which is why its label carries the strongest warning of any modern antidepressant. In a large prospective study of immediate-release bupropion at 300-450 mg/day, the seizure incidence was approximately 0.4% (13 of 3,200 patients); with sustained-release at up to 300 mg/day it was about 0.1% (1 of 1,000). Accumulated data suggest the risk rises almost tenfold between 450 and 600 mg/day. The drug is therefore contraindicated in people with a seizure disorder and in people with current or prior bulimia or anorexia nervosa, and it must not be started during abrupt discontinuation of alcohol, benzodiazepines, barbiturates or antiepileptic drugs. These figures come from the FDA-approved product label, and the label is linked in the references.

Clozapine

Clozapine is among the most epileptogenic of the antipsychotics, and its seizure risk is clearly dose dependent. A published review reports a seizure prevalence of about 1.8% at doses of 300-600 mg/day, rising to about 4.4% at doses above 600 mg/day, and notes that some clinicians regard the plasma concentration as an even better predictor of risk than the dose itself. Seizures have also been reported at much lower doses, so no dose is free of risk. Standard precautions are slow titration and avoidance of other threshold-lowering drugs alongside clozapine.

Tramadol

Tramadol is unusual among opioids because seizures have been reported within the recommended dose range, not only in overdose. The product label states that seizure risk increases with doses above the recommended range and with concomitant use of other drugs that reduce the seizure threshold, including SSRIs, SNRIs, tricyclic antidepressants, other opioids, MAO inhibitors and neuroleptics. Risk is also higher in people with epilepsy, a history of seizures, head trauma, metabolic disorders, alcohol or drug withdrawal, or CNS infections.

Fluoroquinolones, theophylline and other epileptogenic drugs

Cefepime and high-dose penicillins in kidney impairment

Cefepime, a fourth-generation cephalosporin, can cause neurotoxicity including encephalopathy, myoclonus and seizures, sometimes as nonconvulsive status epilepticus. Because the drug is cleared by the kidneys, renal impairment greatly prolongs its half-life and the drug accumulates. The FDA warned in June 2012 that most reported cases occurred in patients with renal impairment who had not received an appropriate dose adjustment, and the label now advises reducing the dose when creatinine clearance is 60 mL/min or below. Between the drug's approval in 1996 and February 2012, 59 cases of nonconvulsive status epilepticus were reported to the FDA, 58 of them in patients with some degree of renal impairment; most cases resolved after cefepime was stopped or dialysed away. High-dose penicillins share the same GABA-antagonist mechanism, which is why the checklist groups them together with a kidney-impairment qualifier.

Lithium toxicity, withdrawal and stimulants

Metabolic causes

Neurologic causes

A prior unprovoked seizure indicates an intrinsically lower threshold and is the single most informative historical factor. Traumatic brain injury raises risk, especially with loss of consciousness or intracranial bleeding; stroke does the same, both early after the event and months later. CNS infections such as meningitis and encephalitis can cause seizures during the illness and leave a lasting predisposition. Any intracranial lesion, including a tumour, abscess or arteriovenous malformation, is a structural reason for a lowered threshold. In pregnancy, severe pre-eclampsia and eclampsia can cause seizures and demand urgent obstetric evaluation rather than watchful waiting. These factors cannot be removed the way a drug can, but recognising them changes how aggressively the reversible factors are pursued.

Other factors: sleep deprivation and febrile seizures

Severe sleep deprivation lowers the seizure threshold, including in people with established epilepsy; it is also one of the easiest factors to overlook on a busy ward or in a student cramming for exams. Fever in a young child is the classic setting for febrile seizures, which are age specific (typically under five years) and usually benign, but which still merit a clinical assessment to exclude a serious cause of the fever.

How the score works and how to use the checklist

1. Press "Calculate risk summary". The panel shows the total out of 26, the band, a breakdown by category, and a band-specific action list.
2. Act on the band, not the number. Lower risk means continue routine care and re-check if anything changes. Moderate risk means a medication review and basic blood tests. Higher risk means an urgent review of every threshold-lowering drug, prompt correction of metabolic factors, and consideration of neurology input.
3. Re-run the checklist when the picture changes. A new prescription, a withdrawal situation, an intercurrent illness or a pregnancy can move a patient between bands.

What to do with your result

Limitations

Frequently asked questions

Medically reviewed by Dr. Taimoor Asghar, Physician and Community Medicine Researcher.