Can Chemotherapy Cause Seizures as a Side Effect?

Chemotherapy can be associated with seizures in certain situations, though it is not a common side effect for most regimens. Seizures may arise due to direct drug neurotoxicity, treatment‑related syndromes (like PRES), metabolic disturbances, interactions with other medicines, or the underlying cancer itself (especially brain tumors). Recognizing symptoms early and having a clear plan for first aid and medical evaluation helps keep you safe. Posterior reversible encephalopathy syndrome (PRES) has been reported after specific agents such as gemcitabine, presenting with seizures and visual changes, and typically improves when identified and treated promptly. [PM7] Symptoms of seizures can also worsen or appear in people whose cancers involve the brain or its coverings; in those cases, antiseizure medications are often part of care. ^[1]

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How Seizures Can Happen During Cancer Treatment

• Direct neurotoxicity of certain drugs
  Some chemotherapy and supportive agents may lower seizure threshold or provoke neurotoxicity in susceptible people; for example, gemcitabine has been linked to PRES with seizures. [PM7]

• Tumor‑related epilepsy
  Brain tumors frequently cause seizures, and overall cancer care (surgery, radiotherapy, chemotherapy) can change seizure patterns; notably, in low‑grade gliomas, chemotherapy like temozolomide may actually reduce seizure frequency in many patients. ^[2] In clinical updates on oligodendroglioma, chemotherapy regimens including temozolomide or PCV have shown seizure reduction in subsets of patients. ^[3]

• Metabolic or vascular complications
  Treatment phases (e.g., induction therapy in pediatric leukemia) can be associated with cerebrovascular complications where seizures are common early signs, underscoring the need for prompt imaging and assessment. [PM8]

• Interactions with other medicines
  Anticonvulsant and cancer drug interactions can alter drug levels; strong enzyme‑inducing antiseizure drugs (like carbamazepine) can significantly lower exposure to certain targeted therapies, potentially reducing their activity. [PM21] Combination antiseizure therapy also changes levels (e.g., valproate raises lamotrigine concentrations), so monitoring helps maintain safety. [PM22]

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Warning Signs to Watch For

• New or worsening headaches, vision changes, confusion, or sudden neurological symptoms may precede seizures in treatment‑related syndromes like PRES. Early recognition and imaging can prevent complications. [PM7]
• In pediatric leukemia care, seizures and altered consciousness during intensive therapy should prompt urgent evaluation, often with MRI. [PM8]

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What To Do If a Seizure Happens (First Aid)

• Keep the person safe: gently ease them to the floor, turn them on their side, and cushion the head; remove nearby hazards. ^[4]
• Time the seizure and do not put anything in the mouth or try to restrain movements. ^[5]
• Call emergency services if the seizure lasts longer than 5 minutes, repeats, occurs in water, causes injury, or if it’s the first seizure. ^[6]

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Medical Evaluation and Acute Management

• Seek urgent care after any first seizure or a change from usual seizure pattern to check for reversible triggers (electrolytes, infections, imaging as needed). In cancer settings, teams will consider treatment‑related syndromes like PRES and adjust therapy. [PM7]
• If there is ongoing or prolonged seizure activity (status epilepticus), care teams follow stepwise protocols with benzodiazepines first, then antiseizure drugs, and escalate to anesthetics if needed, while addressing airway and glucose. Fast treatment helps prevent brain injury. [PM11]

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Prevention and Coping Strategies

• Medication planning

  • For people at high risk of treatment‑related neurotoxicity (e.g., CAR‑T related ICANS), clinicians sometimes consider seizure prophylaxis such as levetiracetam. ^[7]
  • If seizures occur, antiseizure drugs are typically prescribed, and choices consider drug‑drug interactions with cancer therapies; avoiding strong enzyme inducers with sensitive oncology drugs can be important. ^[1] [PM21]

• Monitoring for interactions

  • Carbamazepine can lower exposure to targeted agents like erdafitinib; your oncology team may avoid or substitute antiseizure medications to protect cancer treatment efficacy. [PM21]
  • Adding valproate can increase lamotrigine levels within weeks; therapeutic drug monitoring helps balance effectiveness and side effects. [PM22]

• Lifestyle and safety steps

  • Maintain regular sleep, manage stress, and avoid missed doses of medicines.
  • Create a seizure action plan with caregivers and keep a list of medicines.
  • Follow first‑aid guidelines and know when to call for emergency help. ^{[4] [6]}

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Special Context: Brain Tumors

• In low‑grade gliomas, seizures are very common and sometimes hard to control; surgery, radiotherapy, and certain chemotherapies can reduce seizure frequency, and care plans often combine oncology treatment with antiseizure management for best results. ^{[2] [3]}

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Quick Reference Table: Seizures in Cancer Care

Scenario	Typical driver	Key action
New seizure after chemo (e.g., gemcitabine)	Treatment‑related PRES	Urgent imaging, control BP, adjust therapy; neurological care. [PM7]
Brain tumor with frequent seizures	Tumor‑related epilepsy	Oncologic therapy plus antiseizure meds; monitor response. [2] [3]
Seizure during intensive leukemia therapy	Cerebrovascular/metabolic events	Rapid evaluation; MRI; supportive care. [PM8]
On antiseizure meds with targeted therapy	Drug‑drug interactions	Avoid strong inducers; adjust dosing; TDM. [PM21] [PM22]
Recurrent/prolonged seizures	Status epilepticus	Benzodiazepines first, then antiseizure drugs; protect airway. [PM11]

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Bottom Line

• Seizures can occur during cancer treatment, but they are relatively uncommon and often preventable or manageable with early recognition, appropriate first aid, and careful coordination between oncology and neurology. [PM7]
• For brain tumors, seizures are frequent to start with, and chemotherapy may reduce them in many cases when part of comprehensive care. ^{[2] [3]}
• Work with your care team to choose antiseizure medicines that fit your cancer regimen and minimize interactions, and keep a clear emergency plan at home. [PM21] [PM22] ^{[4] [6]}