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Difference between revisions of "Phenytoin toxicity"
From WikEM
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==Evaluation== | ==Evaluation== | ||
{{Phenytoin toxicity level chart}} | {{Phenytoin toxicity level chart}} | ||
+ | *[https://www.mdcalc.com/phenytoin-dilantin-correction-albumin-renal-failure#evidence| Correct for albumin level] | ||
+ | **Free phenytoin concentration determines toxicity | ||
+ | **Hypoalbuminemia results in higher free phenytoin concentration | ||
+ | *Other laboratory testing | ||
+ | **LFTs, hepatic dysfunction increases risk of phenytoin toxicity | ||
+ | **CBC, frequently show eosinophilia or marked leukocytosis | ||
+ | **Total CK | ||
+ | **[[ECG]], may see arrhythmias, AV block, or sinus arrest with junctional or ventricular escape | ||
+ | **POC glucose, rule out hypoglycemia as cause of AMS | ||
+ | **[[Acetaminophen]] and [[salicylate toxicity|salicylate]] levels, rule out common coingestion | ||
+ | ** Urine pregnancy test | ||
==Management== | ==Management== |
Revision as of 00:08, 10 May 2017
Contents
Background
- Mortality is extremely rare after intentional overdose if good supportive care is provided
- Rapid IV dosing carries greatest risk (due to propylene glycol constituent of IV form → myocardia depression & cardiac arrest)
- 90% protein bound; dialysis ineffective
Clinical Features
- CV (only with IV form)
- Bradycardia
- Hypotension
- Vfib
- Asystole
- Neuro
- Nystagmus
- First only with forced lateral gaze; later becomes spontaneous
- May disappear at higher levels
- Ataxia
- Decreased LOC
- Nystagmus
- GI
- Skin
- tissue infiltration (IV) → "purple glove syndrome"
- edema, pain, ischemia, tissue necrosis, compartment syndrome
- Anticonvulsant hypersensitivity syndrome
- Fever, eosinophilia, rash, pseudolymphoma, SLE, pancytopenia, hepatitis, pneumonitis, pharyngitis, rhabdomyolysis
- Mortality rate of 10%
Differential Diagnosis
Evaluation
Toxicity symptoms by phenytoin level^
Level | Sypmtoms |
>10 | Usually no symptoms |
10-20 | Occasional mild nystagmus |
20-30 | Nystagmus |
30-40 | Ataxia, slurred speech, Nausea/vomiting |
40-50 | Lethargy, confusion |
>50 | Coma, seizure (rare) |
^Provides a rough guide only; neither sensitive nor specific
- Correct for albumin level
- Free phenytoin concentration determines toxicity
- Hypoalbuminemia results in higher free phenytoin concentration
- Other laboratory testing
- LFTs, hepatic dysfunction increases risk of phenytoin toxicity
- CBC, frequently show eosinophilia or marked leukocytosis
- Total CK
- ECG, may see arrhythmias, AV block, or sinus arrest with junctional or ventricular escape
- POC glucose, rule out hypoglycemia as cause of AMS
- Acetaminophen and salicylate levels, rule out common coingestion
- Urine pregnancy test
Management
- Detoxification
- Bradyarrhythmias
- Atropine, pacing
- Hypotension
Disposition
- Cannot base on phenytoin level (erratic absorption after PO overdose)
- Consider discharge if patient has only mild symptoms and serial phenytoin levels decline