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wikitox:3.1.3_seizures [2018/09/01 09:00] (current)
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 +====== Seizures ======
 +Kent R Olsen, MD (to end of table)
 +Seizures are a common complication of drug overdose and poisoning and have multiple causes. (See Table) Most drug-induced seizures are self-limited,​ but prolonged or repeated seizures may need treatment.
 +  * The usual intervention is diazepam or another benzodiazepine,​ in repeated boluses as needed.
 +  * The second line of treatment is phenobarbital (15 mg/kg over 45 minutes).
 +  * Seizures not responsive to phenobarbital may require induction of coma with pentobarbital or propofol. Phenytoin is rarely used for drug-induced seizures, and has been shown to be relatively ineffective for seizures caused by theophylline and TCAs.
 +  * If isoniazid is suspected, or if the cause of seizures is unknown and the patient continues to fit, a trial of intravenous pyridoxine (Vitamin B-6) is indicated. Give 5 gm initially, and if the dose of INH ingested is known, give a gram equivalent amount of pyridoxine (e.g., give 10 gm pyridoxine for a 10-gm INH overdose).
 +Prolonged or recurrent seizures associated with drug intoxication or poisoning may be due to secondary complications,​ such as hyperthermia,​ stroke or hypoglycemia,​ and these should be ruled out and treated.
 +Multiple or prolonged seizures are an indication for consideration of enhanced removal of some poisons, such as theophylline,​ lithium or carbamazepine.
 +|**Selected Causes of Seizures** |**Treatment/​Comments** |
 +|Tricyclic antidepressants|Usually associated with prolongation of the QRS interval on the ECG. Treat seizures with benzodiazepines;​ add phenobarbital if needed. Check for hyperthermia in patients with multiple or prolonged seizures.|
 +|Newer antidepressants|Bupropion and venlafaxine most commonly associated with seizures but all newer drugs have been reported to cause seizures in overdose. Treat with benzodiazepines;​ add phenobarbital if needed. Check for hyperthermia/​serotonin syndrome in patients with multiple or prolonged seizures.|
 +|Amphetamines/​cocaine|Seizures usually accompanied by other manifestations of sympathetic system overstimulation (e.g., hypertension,​ tachycardia). Check for hyperthermia in patients with multiple or prolonged seizures. Consider possibility of intracranial hemorrhage or ischemic stroke.|
 +|Isoniazid (INH)|Patients with INH overdose often have lactic acidosis out of proportion to the number and duration of seizures. Treat with benzodiazepines initially; if pyridoxine (vitamin B-6) is available, give at least 5 gm intravenously,​ and if the dose ingested is known, give a gram equivalent dose of pyridoxine.|
 +|Carbamazepine|Seizures may occur as a result of overdose (usually only with high blood levels) or may be breakthrough seizures in a patient with underlying epilepsy who has stopped taking a second antiepileptic medication. Consider hemodialysis if seizures are recurrent or the serum level exceeds 40 mg/L.|
 +|Theophylline|Seizures after acute overdose common if serum levels exceed 90-100 mg/L; may be seen in patients with chronic intoxication at lower levels (e.g., 20-70 mg/L). Acute overdose with level over 90-100 mg/L should be referred for urgent hemodialysis.|
 +|Organophosphates/​carbamates|Typical cholinergic excess (pinpoint pupils, hypersalivation,​ bronchorrhea,​ vomiting and diarrhea)|
 +|Withdrawal from alcohol|Tremor,​ anxiety, tachycardia,​ autonomic instability,​ hallucinations|
 +The following drugs directly cause seizures (though so does hypotension).
 +  * [[:​wikitox:​|Propranolol and oxprenolol]]
 +  * [[:​wikitox:​|Tricyclic antidepressants]]
 +  * [[:​wikitox:​|Antipsychotic drugs]] (particularly chlorpromazine and thioridazine)
 +  * [[:​wikitox:​|Anticonvulsants]] (particularly [[:​wikitox:​barbiturates|]],​ carbamazepine and phenytoin)
 +  * [[:​wikitox:​|Dextropropoxyphene]]
 +  * [[:​wikitox:​antimalarial_drugs|Antimalarial drugs]] (chloroquine,​ quinine)
 +  * [[:​wikitox:​|Antiarrhythmic drugs]]
 +  * [[:​wikitox:​|Orphenadrine]]
 +  * [[:​wikitox:​|Lithium]]
 +[[:​wikitox:​status_epilepticus_and_treatment_of_seizures|Seizures]] are commonly seen in severe poisonings with all the following drugs:
 +  * Tricyclic antidepressants
 +  * Anticonvulsants (particularly carbamazepine and phenytoin)
 +  * Antimalarial drugs (chloroquine,​ quinine)
 +  * [[:​wikitox:​|Beta blockers]] (particularly propranolol)
 +  * Antiarrhythmic drugs
 +  * Orphenadrine
 +  * [[:​wikitox:​|Lithium]]
 +  * Chloral hydrate
 +  * Adrenergic drugs ([[:​wikitox:​|theophylline]],​ [[:​wikitox:​|cocaine]] and amphetamines)
 +  * Drugs that lead to tissue hypoxia, acidosis or hypoglycaemia ( [[:​wikitox:​|CO]],​ [[:​wikitox:​|organochlorines]],​ [[:​wikitox:​|hypoglycaemic drugs]], [[:​wikitox:​|insulin]],​ isoniazid, [[:​wikitox:​|salicylates]] etc.)
 +===== RESOURCES =====
 +Powerpoint presentation on drug-induced seizures Kent R Olson MD 2006: {{:​wikitox:​seizures_olsen_2006.ppt|Seizures Olsen 2006.ppt}} ​ [397 KB] \\
 +Powerpoint presentation on drug-induced seizures by Bob Hoffman 2011: {{:​wikitox:​seizures_hoffman_2011.ppt|Seizures Hoffman 2011.ppt}} ​ [3.3 MB]
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