Phenytoin: Difference between revisions
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==Adverse Reactions== | ==Adverse Reactions== | ||
''See [[phenytoin toxicity]] for overdose'' | |||
===Serious=== | ===Serious=== | ||
*V-Fib (IV) | *[[V-Fib]] (IV) | ||
*Hypotension (IV) | *[[Hypotension]] (IV) | ||
*CV collapse (IV) | *CV collapse (IV) | ||
*AV conduction disturbance (IV) | *AV conduction disturbance (IV) | ||
*Hepatotoxicity | *[[Hepatotoxicity]] | ||
*Thrombocytopenia | *[[Thrombocytopenia]] | ||
*Leukopenia | *[[Leukopenia]] | ||
*Agranulocytosis | *[[Agranulocytosis]] | ||
*Pancytopenia | *[[Pancytopenia]] | ||
*Megaloblastic anemia | *[[Megaloblastic anemia]] | ||
*Stevens-Johnson syndrome | *[[Stevens-Johnson syndrome]] | ||
*Toxic epidermal necrolysis | *[[Toxic epidermal necrolysis]] | ||
*Drug rash (w/ eosinophilia) | *Drug rash (w/ eosinophilia) | ||
*Tissue necrosis (IV) | *Tissue necrosis (IV) | ||
*Purple glove syndrome (IV) | *Purple glove syndrome (IV) | ||
*Anaphylaxis | *[[Anaphylaxis]] | ||
*Lymphoma | *[[Lymphoma]] | ||
*Lupus | *[[Lupus]] | ||
*Osteomalacia | *Osteomalacia | ||
*Toxic delirium | *Toxic delirium | ||
*SI | *[[SI]] | ||
*Periarteritis nodosa | *Periarteritis nodosa | ||
*Withdrawal seizures with abrupt discontinuation | *Withdrawal seizures with abrupt discontinuation | ||
===Common=== | ===Common=== | ||
* | *[[Nausea/vomiting]] | ||
*Rash | *[[Rash]] | ||
*Nystagmus | *[[Nystagmus]] | ||
*Ataxia | *[[Ataxia]] | ||
*Slurred speech | *Slurred speech | ||
*Dizziness | *[[Dizziness]] | ||
*Confusion | *Confusion | ||
*Paresthesia | *[[Paresthesia]] | ||
*Blurred vision | *Blurred vision | ||
*Somnolence | *Somnolence | ||
*Constipation | *[[Constipation]] | ||
*HA | *[[HA]] | ||
*Insomnia | *[[Insomnia]] | ||
*Gingival hyperplasia | *Gingival hyperplasia | ||
*Tremor | *Tremor | ||
Revision as of 01:02, 1 October 2015
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: 15-20 mg/kg IV; if ineffective, can give 10 mg/kg IV 20 min after first dose
- Maintenance dose: 100 mg PO/IV q 6-8hrs
- Start 12 hours after loading dose
- Seizure disorder
- 300-400 mg/day divided into 2-3 doses/day (Max 400 mg/dose)
- May give 4-7 mg/kg/day divided into 2-3 doses/day
- Consider loading dose: 15-20 mg/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: 10-20 mg/kg IV in 3 doses 2-4 hrs apart (max 400 mg/dose)
- 4-6 mg/kg/day IV divided into 2-3 doses/day
- Can give IM route, though IV prefered
- 100-200 mg IM q 4 hrs x 1 week
- 150% PO dose by IM route if previously on medication
Pediatric Dosing
- Status Epilepticus
- Loading dose: 15-20 mg/kg IV; if ineffective, can give 10 mg/kg IV 20 min after first dose
- Max 1500 mg/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: 8-10 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
- 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
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 (w/ 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
Sources
Epocrates Medscape