Phenytoin: Difference between revisions
(Text replacement - "w/ " to "with ") |
Neil.m.young (talk | contribs) (Text replacement - "0 mg" to "0mg") |
||
| Line 6: | Line 6: | ||
==Adult Dosing== | ==Adult Dosing== | ||
===[[Status epilepticus]]=== | ===[[Status epilepticus]]=== | ||
*Loading dose: 15- | *Loading dose: 15-20mg/kg IV; if ineffective, can give 10mg/kg IV 20 min after first dose | ||
*Maintenance dose: | *Maintenance dose: 100mg PO/IV q 6-8hrs | ||
*Start 12 hours after loading dose | *Start 12 hours after loading dose | ||
===[[Seizure]] disorder=== | ===[[Seizure]] disorder=== | ||
*300- | *300-400mg/day divided into 2-3 doses/day (Max 400mg/dose) | ||
*May give 4-7 mg/kg/day divided into 2-3 doses/day | *May give 4-7 mg/kg/day divided into 2-3 doses/day | ||
*Consider loading dose: 15- | *Consider loading dose: 15-20mg/kg divided into 2-3 doses given 2-4 hrs apart | ||
*Adjust dose on response and serum levels | *Adjust dose on response and serum levels | ||
*Available in extended or immediate release | *Available in extended or immediate release | ||
===[[Seizure]] prophylaxis (neurosurgery)=== | ===[[Seizure]] prophylaxis (neurosurgery)=== | ||
*Loading dose: 10- | *Loading dose: 10-20mg/kg IV in 3 doses 2-4 hrs apart (max 400mg/dose) | ||
*4-6 mg/kg/day IV divided into 2-3 doses/day | *4-6 mg/kg/day IV divided into 2-3 doses/day | ||
*Can give IM route, though IV prefered | *Can give IM route, though IV prefered | ||
**100- | **100-200mg IM q 4 hrs x 1 week | ||
**150% PO dose by IM route if previously on medication | **150% PO dose by IM route if previously on medication | ||
==Pediatric Dosing== | ==Pediatric Dosing== | ||
===[[Seizure (peds)|Status epilepticus]]=== | ===[[Seizure (peds)|Status epilepticus]]=== | ||
*Loading dose: 15- | *Loading dose: 15-20mg/kg IV; if ineffective, can give 10mg/kg IV 20 min after first dose | ||
*Max | *Max 1500mg/day | ||
*Start maintenance 12 hrs after loading dose | *Start maintenance 12 hrs after loading dose | ||
| Line 33: | Line 33: | ||
''All doses are divided into 2-3 doses/day; always start at 5 mg/kg/day and titrate based on effect and serum levels'' | ''All doses are divided into 2-3 doses/day; always start at 5 mg/kg/day and titrate based on effect and serum levels'' | ||
*<6 mo: 5-8 mg/kg/day PO/IV | *<6 mo: 5-8 mg/kg/day PO/IV | ||
*6mo-4 yrs: 8- | *6mo-4 yrs: 8-10mg/kg/day PO/IV | ||
*4-7yrs: 7.5-9 mg/kg/day PO/IV | *4-7yrs: 7.5-9 mg/kg/day PO/IV | ||
*7-10 yrs: 7-8 mg/kg/day PO/IV | *7-10 yrs: 7-8 mg/kg/day PO/IV | ||
Revision as of 02:04, 20 July 2016
General
- Type: Anticonvulsants
- Dosage Forms: capsules 50, 100, 200, 300 125/5 mL IM/IV
- Common Trade Names: Dilantin, Phenytek
Adult Dosing
Status epilepticus
- Loading dose: 15-20mg/kg IV; if ineffective, can give 10mg/kg IV 20 min after first dose
- Maintenance dose: 100mg PO/IV q 6-8hrs
- Start 12 hours after loading dose
Seizure disorder
- 300-400mg/day divided into 2-3 doses/day (Max 400mg/dose)
- May give 4-7 mg/kg/day divided into 2-3 doses/day
- Consider loading dose: 15-20mg/kg divided into 2-3 doses given 2-4 hrs apart
- Adjust dose on response and serum levels
- Available in extended or immediate release
Seizure prophylaxis (neurosurgery)
- Loading dose: 10-20mg/kg IV in 3 doses 2-4 hrs apart (max 400mg/dose)
- 4-6 mg/kg/day IV divided into 2-3 doses/day
- Can give IM route, though IV prefered
- 100-200mg IM q 4 hrs x 1 week
- 150% PO dose by IM route if previously on medication
Pediatric Dosing
Status epilepticus
- Loading dose: 15-20mg/kg IV; if ineffective, can give 10mg/kg IV 20 min after first dose
- Max 1500mg/day
- Start maintenance 12 hrs after loading dose
Seizure disorder
All doses are divided into 2-3 doses/day; always start at 5 mg/kg/day and titrate based on effect and serum levels
- <6 mo: 5-8 mg/kg/day PO/IV
- 6mo-4 yrs: 8-10mg/kg/day PO/IV
- 4-7yrs: 7.5-9 mg/kg/day PO/IV
- 7-10 yrs: 7-8 mg/kg/day PO/IV
- 10-16 yrs: 6-7 mg/kg/day PO/IV
- >16 yrs use adult dosing
- For immediate release. Extended release available for ages >7 at same dosages.
Special Populations
- Pregnancy Rating: D
- Lactation: Likely safe; limited information. Use caution.
- Renal Dosing
- Adult: No oral loading regimen
- Pediatric: No adjustment
- Hepatic Dosing
- Adult: No oral loading regimen
- Pediatric: Decrease dose, amount not defined
Contraindications
- Allergy to class/drug
- Sinus brady/SA block/2nd-3rd AV block
- Adams-Stokes syndrome
- Avoid abrupt withdrawl
- Caution:
- CV disease
- Hypotension
- Alcohol use
- HLA-B 1502 positive
- Renal impairment
- Hepatic impairment
- Porphyria
- DM
- Thyroid disease
- Depression
- Elderly
Adverse Reactions
See phenytoin toxicity for overdose
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
Serious
- V-Fib (IV)
- Hypotension (IV)
- CV collapse (IV)
- AV conduction disturbance (IV)
- Hepatotoxicity
- Thrombocytopenia
- Leukopenia
- Agranulocytosis
- Pancytopenia
- Megaloblastic anemia
- Stevens-Johnson syndrome
- Toxic epidermal necrolysis
- Drug rash (with eosinophilia)
- Tissue necrosis (IV)
- Purple glove syndrome (IV)
- Anaphylaxis
- Lymphoma
- Lupus
- Osteomalacia
- Toxic delirium
- SI
- Periarteritis nodosa
- Withdrawal seizures with abrupt discontinuation
Common
- Nausea/vomiting
- Rash
- Nystagmus
- Ataxia
- Slurred speech
- Dizziness
- Confusion
- Paresthesia
- Blurred vision
- Somnolence
- Constipation
- HA
- Insomnia
- Gingival hyperplasia
- Tremor
- Lymphadenopathy
- Coarse facies
- Hyperglycemia
- Osteomalacia
- Phlebitis (IV)
- Peyronie disease
- Taste change
Pharmacology
- Half-life: 7-42 hrs
- Metabolism: liver; CYP450: 2C9 and 2C19
- Excretion: bile and urine
- Mechanism of Action: effects neuronal voltage-dependent NA and CA channels
See Also
References
- Epocrates
- Medscape