Toxic and drug-induced seizures
Which poisons, medicines and withdrawal states cause seizures, why benzodiazepines come first and phenytoin doesn't belong, the antidotes that stop specific toxic seizures, and what follow-up a provoked seizure needs.
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Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Toxic seizures are usually single or few, brief and generalised. Status epilepticus does occur, particularly with isoniazid, theophylline, bupropion and withdrawal.
- Glucose and sodium first. Hypoglycaemia and hyponatraemia are drug-caused seizures with a quick fix.
- Benzodiazepines are first line. Phenobarbital or an anaesthetic agent is second line. Phenytoin doesn't belong in toxic seizures.
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Sources
- Therapeutic Guidelines: Toxicology and Toxinology (2024 update)AU/NZTherapeutic Guidelines Limited, 2024
- Whyte IM, Dawson AH, Buckley NA. Relative toxicity of venlafaxine and selective serotonin reuptake inhibitors in overdose compared to tricyclic antidepressants. QJM 2003;96:369-74AU/NZQJM, 2003
- Ryan NM, Isbister GK. Tramadol overdose causes seizures and respiratory depression but serotonin toxicity appears unlikely. Clin Toxicol 2015;53:545-50AU/NZClinical Toxicology, 2015
- Pyridoxine: antidote stocking recommendationsAU/NZQueensland Poisons Information Centre, 2023
- Assessing Fitness to Drive: seizures and epilepsy (section 6.2)AU/NZAustroads
- Trinka E et al. A definition and classification of status epilepticus: report of the ILAE Task Force on Classification of Status Epilepticus. Epilepsia 2015;56:1515-23International League Against Epilepsy, 2015
- Last updated
- 14 November 2026
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