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Toxicity, Phenytoin: Treatment & Medication
Updated: Jul 15, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Treatment
Prehospital Care
- The usual measures of airway maintenance, breathing assessment, and circulatory support are indicated.
Emergency Department Care
- Support airway, breathing, and circulation.5
- Obtain IV access, provide supplemental oxygen, and place on a cardiac monitor.
- Consider the risks versus the benefits of orogastric lavage; it rarely offers any advantage over activated charcoal and cathartic use.
- Administer multiple dose activated charcoal6 every 2-6 hours until passage of charcoal stool, loss of bowel sounds, or improved clinical condition is observed. This may be difficult because nausea and emesis may complicate phenytoin toxicity. Activated charcoal may precipitate vomiting, aspiration pneumonia, or electrolyte disturbances.
- Hemodialysis or hemoperfusion are ineffective for enhancing elimination.
- The treatment of hypotension secondary to IV infusion includes decreasing the rate of infusion, intravenous fluids, and, possibly, vasopressors.
Consultations
- Consult neurology department personnel for moderate-to-severe reactions caused by chronic therapy. Patients require close follow-up and changes in anticonvulsant medication.
- Patients with serious complications (eg, dysrhythmias, hemodynamic instability, altered mental status, severe ataxia, coma, seizures) following a toxic exposure require hospital admission for further monitoring and treatment.7
- Consultation of psychiatry department personnel for intentional overdoses is mandatory.
- Consult a plastic surgeon for extravasation injuries.
- Consult the regional poison control center or a local medical toxicologist (certified by the American Board of Medical Toxicology or the American Board of Emergency Medicine) for additional information and patient care recommendations.
Medication
Treatment of phenytoin toxicity is primarily focused on limiting the systemic burden of phenytoin by GI decontamination and management of any seizures that may occur with benzodiazepines.
GI decontaminant
Multiple dose activated charcoal is thought to enhance the elimination of phenytoin that was administered orally or intravenously.
Activated charcoal (Liqui-Char)
Preferred GI decontamination method when decontamination is desired. It may be administered with a cathartic (eg, 70% sorbitol), except in young pediatric patients in whom electrolyte disturbances may be of concern. Limited benefit if administered greater than 1 h after ingestion.
Adult
1 g/kg (50-100 g) PO
Pediatric
1-2 g/kg (15-30 g) PO
<2 years: cathartic not recommended
Effectiveness of other medications decreases with coadministration; do not mix charcoal with sherbet, milk, or ice cream (decreases adsorptive properties)
Documented hypersensitivity; poisoning or overdose of mineral acids and alkalies; unprotected airway with absent gag reflex
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Monitor for presence of bowel sounds to minimize risk of charcoal ileus; not very effective in poisonings of ethanol, methanol, and iron salts; can administer in early stages of gastric lavage; without sorbitol, gastric lavage returns are black
Benzodiazepines
Used for seizure control, although seizures in the presence of toxic levels of phenytoin are rare.
Lorazepam (Ativan)
DOC for drug-induced seizures. Longer duration of action compared to the other agents.
Adult
0.044 mg/kg (2-4 mg) IV, titrate to effect
Status epilepticus: 4 mg IV over 2-5 min; may repeat second dose in 10-15 min prn; not to exceed 8 mg/dose
Pediatric
Infants and children: 0.02-0.1 mg/kg IV slowly over 2-5 min; repeat in 10-15 min at 0.05 mg/kg prn; not to exceed 4 mg/dose
Adolescents: 0.07 mg/kg IV slowly over 2-5 min; repeat in 10-15 min prn; not to exceed 4 mg/dose
Effects are potentiated by narcotics, barbiturates, MAOIs, and other antidepressants
Documented hypersensitivity; preexisting CNS depression, hypotension, and narrow-angle glaucoma
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution in renal or hepatic impairment, myasthenia gravis, organic brain syndrome, or Parkinson disease; monitor for respiratory depression with high or repeated doses; contains benzyl alcohol, which may be toxic to infants in high doses
Midazolam (Versed)
IV/IM formulation with short duration of sedation. Used as alternative in termination of refractory status epilepticus. Because water soluble, takes approximately 3 times longer than diazepam to peak EEG effects. Thus, clinician must wait 2-3 min to fully evaluate sedative effects before initiating procedure or repeating dose.
Adult
0.05 mg/kg IV; repeat prn
Pediatric
Administer as in adults
Sedative effects of midazolam may be antagonized by theophyllines; narcotics and erythromycin may accentuate sedative effects of midazolam because of decreased clearance
Documented hypersensitivity; preexisting hypotension, narrow-angle glaucoma, and sensitivity to propylene glycol (diluent)
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution in congestive heart failure, pulmonary disease, renal impairment, and hepatic failure; monitor for respiratory depression with high or repeated doses
Diazepam (Valium)
Depresses all levels of CNS (eg, limbic and reticular formation), possibly by increasing activity of GABA. Commonly available, also useful for treatment of seizures or agitation.
Adult
0.1-0.2 mg/kg IV or 5-10 mg IV q10-15min until symptoms resolve; not to exceed 30 mg
Pediatric
30 days to 5 years: 0.2-0.5 mg IV (slowly) q2-5min until symptoms resolve; not to exceed 5 mg
>5 years: 1 mg IV (slowly) q2-5min until symptoms resolve; not to exceed 10 mg
Increases toxicity of benzodiazepines in CNS with coadministration of phenothiazines, barbiturates, alcohols, and MAOIs
Documented hypersensitivity; hypotension or narrow-angle glaucoma
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution with other CNS depressants, low albumin levels, or hepatic and renal disease (may increase toxicity); monitor for respiratory depression with high or repeated doses
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| Differential Diagnoses & Workup: Toxicity, Phenytoin |
 Treatment & Medication: Toxicity, Phenytoin |
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Further Reading
Keywords
phenytoin toxicity, phenytoin poisoning, phenytoin exposure, anticonvulsant drug, seizure disorder, phenytoin overdose, elevated phenytoin levels, status epilepticus, phenytoin ingestion, seizure treatment, treatment of seizure
