HPI

• 55 yo M presents 2.5 hrs s/p intentional ingestion of 180 pills of Dilantin ER 100 mg. 
• Other medications in the home included Effexor, Klonopin, and metformin. Denied having access to any OTC medications such as acetaminophen and ibuprofen. Denied access to any other medications in the home. 
• PMhx: CAD, NIDDM, epilepsy

Physical exam:

Vitals: T 98.1 HR 90 BP 136/101 RR 18 SpO2 97% RA

• AAOx3, conversant, cooperative, protecting airway.
• CN II-XII intact. Strength 5/5 and equal b/l in upper and lower extremities. Sensation to light touch intact and equal b/l over C5-T1, L3-S1 dermatomes. Normal finger-to-nose and heel-shin b/l. No nystagmus, dysmetria, dysdiadochokinesia, clonus, or tremor.

Labs:

AG 17, Mg 1.4, phos 2.7 Acetaminophen < 5.0 Salicylate < 0.3 UDS negative

ECG NSR with normal intervals, no ST/T changes

Phenytoin level  29.4 μg/mL (ref: 10-20)

Management:

• Telemetry monitoring
• Suicide precautions and close observation
• Patient discussed with Poison Control, recommended monitoring for depressed level of consciousness, clonus, and nystagmus
• Activated charcoal was administered 3.5 hrs after ingestion
• Phenytoin levels q4-6hrs
• Admitted to med tele for monitoring 

Discussion: 

• Phenytoin (Dilantin) is an anticonvulsant that acts as a sodium channel antagonist
• The first sign of toxicity is usually nystagmus, which is first elicited with lateral gaze and then may become spontaneous
• As phenytoin levels increase > 30 μg/mL, ataxia, dysarthria, nausea, vomiting, lethargy, and confusion develop
• Cardiac toxicity such as hypotension and bradycardia is only reported with IV phenytoin due to the propylene glycol diluent, and reports of the cardiac effects of phenytoin overdose are usually attributable to other causes.
• For this reason, cardiac monitoring after PO phenytoin overdose is usually unnecessary
• Treatment is supportive, involving the correction of acidosis and electrolyte abnormalities
• Single-dose activated charcoal can be given within 4 hours of an oral ingestion, though the risks of vomiting and aspiration in a somnolent patient must be considered

References:

LoVecchio F. Anticonvulsants. In: Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9th edition. New York, NY: McGraw-Hill Education; 2020: 1283-1289.

Randomized controlled study on the use of multiple-dose activated charcoal in patients with supratherapeutic phenyotin levels. Clinical Toxicology 2012;50(8):764-769. doi: 10.3109/15563650.2012.716159.

Cumpston K, Stomberg P, Wills B, Rose SR. Activated charcoal does not reduce duration of phenytoin toxicity in hospitalized patients. American Journal of Therapeutics 2016;23(3):e773-e777. doi: 10.1097/MJT.0000000000000058.