Phenytoin toxicity: Difference between revisions
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== Background == | ==Background== | ||
*Mortality is extremely rare after intentional overdose if good supportive care is provided | *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 | *Rapid IV dosing carries greatest risk (due to propylene glycol constituent of IV form → myocardia depression & cardiac arrest) | ||
*90% protein bound; dialysis ineffective | *90% protein bound; dialysis ineffective | ||
== Clinical Features == | ==Clinical Features== | ||
*CV (only with IV form) | *CV (only with IV form) | ||
**Bradycardia | **Bradycardia | ||
**Hypotension | **[[Hypotension]] | ||
**Asystole | **[[Vfib]] | ||
**[[Asystole]] | |||
*Neuro | *Neuro | ||
**Nystagmus | **Nystagmus | ||
| Line 18: | Line 17: | ||
**Decreased LOC | **Decreased LOC | ||
*GI | *GI | ||
** | **[[Nausea and vomiting]] | ||
*Skin | *Skin | ||
**tissue infiltration (IV) | **tissue infiltration (IV) → "[[Purple glove syndrome]]" | ||
**edema, pain, ischemia, tissue necrosis, compartment 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== | ||
* | {{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== | ||
*Supportive care is mainstay of treatment | |||
*If intubation needed, standard RSI meds ok, avoid lidocaine (same antidysrhythmic properties as phenytoin) | |||
*If symptomatic bradydysrhythmia: | |||
**[[ACLS: Bradycardia]], Atropine, epinephrine, dopamine are first line | |||
**May consider [[transcutaneous pacing|transcutaneous]] or [[transvenous pacing]] | |||
*Hypotension | |||
**IVF bolus | |||
*Detoxification | |||
**[[Activated charcoal]] PO | |||
**[[Gastric lavage]] and [[whole bowel irrigation]] are '''NOT''' recommended | |||
==Disposition== | ==Disposition== | ||
*Cannot base on phenytoin level (erratic absorption after PO overdose) | *Cannot base on phenytoin level (erratic absorption after PO overdose) | ||
**Consider discharge if | **Consider discharge if patient has only mild symptoms and serial phenytoin levels decline | ||
==See Also== | |||
*[[Phenytoin]] | |||
== | ==References== | ||
<references/> | |||
[[Category: | [[Category:Toxicology]] | ||
Revision as of 01:18, 10 May 2017
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
- Supportive care is mainstay of treatment
- If intubation needed, standard RSI meds ok, avoid lidocaine (same antidysrhythmic properties as phenytoin)
- If symptomatic bradydysrhythmia:
- ACLS: Bradycardia, Atropine, epinephrine, dopamine are first line
- May consider transcutaneous or transvenous pacing
- Hypotension
- IVF bolus
- Detoxification
- Activated charcoal PO
- Gastric lavage and whole bowel irrigation are NOT recommended
Disposition
- Cannot base on phenytoin level (erratic absorption after PO overdose)
- Consider discharge if patient has only mild symptoms and serial phenytoin levels decline