Adult Dosing
Status epilepticus
- 15-20 mg/kg IV x1 dose at a rate not exceeding 50 mg/minute
- May give additional 10 mg/kg IV x1 after 20 min if no response to initial dose
- Maintenance dose: 100 mg IV q6-8 hrs
Seizure prophylaxis in neurosugery
IV Administration
- 4-6 mg/kg/day IV div bid-tid
- Start: Load 10-20 mg/kg IV div in 3 doses 2-4h apart
- Max: 400 mg/dose
- Info: IV route preferred to IM route
IM Administration
- 100-200 mg IM q4h
- Max: x1 week
- Alt: give 150% of usual daily PO dose by IM route div q4h
- Info: decrease usual PO dose by 50% for same duration as IM was used when converting back from IM to PO
Seizure prophylaxis in Subarachnoid Hemorrhage [Non-FDA Approved]
- 15-20 mg/kg IV load at maximum infusion rate of no faster than 50 mg/min; max 1.5 g; maintenance 4-6 mg/kg/day IV
Prophylaxis of seizures in subdural hematoma [Non-FDA Approved]
- Loading dose 15-20 mg/kg IV, no more rapid than 50 mg/min
Pediatric Dosing
Status epilepticus
- Loading dose: 15-20 mg/kg IV at a rate not exceeding 1-3 mg/kg/minute
- Max: 1500 mg/day
- Info: may give additional 10 mg/kg IV x1 after 20min if no response to initial dose
- Maintenance dose: 100 mg IV q6-8 hrs
Seizure prophylaxis in Subarachnoid Hemorrhage [Non-FDA Approved]
- 15-20 mg/kg IV load at maximum infusion rate of no faster than 50 mg/min; max 1.5 g; maintenance 4-6 mg/kg/day IV
Prophylaxis of seizures in subdural hematoma [Non-FDA Approved]
- Loading dose 15-20 mg/kg IV, no more rapid than 50 mg/min
[Outline]
- Severe cardiotoxic reactions and fatalities may occur with atrial and ventricular conduction depression and ventricular fibrillation. Elderly or gravely ill patients are prone to severe complications
- Hypotension may usually occur on administering rapidly by the IV route
- IM route is not recommended for the treatment of status epilepticus as blood levels of phenytoin in the therapeutic range are not readily achieved with doses and methods of administration ordinarily employed
- Lymphadenopathy (local or generalized) including benign lymph node hyperplasia, pseudolymphoma, lymphoma and Hodgkin’s Disease may occur. Involvement of lymph node may occur with or without symptoms and signs resembling serum sickness. Conduct follow-up observation for an extended period and make efforts to achieve seizure control using alternative antiepileptic drugs for all cases of lymphadenopathy
- Increased phenytoin serum levels may occur with acute alcoholic intake while serum levels may decrease with chronic alcoholic use
- Higher incidence of birth defects may occur in children born to women using this drug. Avoid discontinuation of treatment in patients in whom the drug is administered to prevent major seizures, as strong possibility of precipitating status epilepticus with attendant hypoxia and threat to life exists. Discontinuation of the drug may be considered prior to and during pregnancy in individual cases where the severity and frequency of the seizure disorder are such that the removal of medication does not pose a serious threat to the patient; however it cannot be confirmed with any confidence that even minor seizures do not pose some hazard to the developing embryo or fetus. Weigh such considerations in treating or counseling epileptic women of childbearing potential
- Increased incidence of congenital malformation, such as cleft lip/palate and heart malformations in children of women receiving phenytoin have occurred. Reports also suggest that fetal hydantoin syndrome may also develop. Malignancies, including neuroblastoma may also occur in children whose mothers received phenytoin during pregnancy. Periodically measure serum phenytoin levels for the management of a pregnant epileptic patient as a guide to an appropriate adjustment of dosage
- Neonatal coagulation defects may occur within the first 24 hours in babies born to epileptic mothers receiving this drug. Administer Vitamin K to the mothers before and to the neonate after birth to prevent or correct such defect
- Avoid addition of Phenytoin Sodium Injection to IV infusion due to lack of solubility and resultant precipitation. Follow each injection of IV Phenytoin Sodium Injection by an injection of sterile saline through the same needle or IV catheter to avoid local venous irritation due to the alkalinity of the solution. Avoid continuous infusion
- Soft tissue irritation and inflammation may occur at the site of injection with and without extravasation of IV phenytoin. Soft tissue irritation with slight tenderness to extensive necrosis, sloughing, and in rare instances leading to amputation may occur; avoid improper administration including SC or perivascular injection to prevent such possibility
- Edema, discoloration and pain of the distal limb may occur following peripheral IV injection. Skin necrosis, limb ischemia may occur requiring interventions such as fasciotomies, skin grafting and amputation
- Toxicity may occur in patients with impaired liver function, elderly patients, or those who are gravely ill
- Discontinue therapy on development of skin rash. On suspicion of exfoliative, purpuric, or bullous rash or lupus erythematosus, Stevens-Johnson syndrome avoid resuming use of this drug and consider alternative therapy. If the rash is of a milder type (measles-like or scarlatiniform) therapy may be resumed after complete disappearance of rash. On recurrence of rash upon reinstitution of therapy, further phenytoin medication is contraindicated
- Hyperglycemia may occur. This drug may also raise the serum glucose level in diabetic patients
- This drug is not indicated for seizures due to hypoglycemic or other metabolic causes. Perform appropriate diagnostic procedures as indicated
- Phenytoin is not effective for absence (petit mal) seizures. On presence of tonic-clonic (grand-mal) and absence (petit mal) seizures combined drug therapy may be needed
- Delirium, psychosis, encephalopathy or rarely irreversible cerebellar dysfunction may occur due to sustained serum levels of phenytoin >optimal range. Consider dose reduction of phenytoin on excessive plasma levels and termination on persistence of symptoms
- Severe cardiotoxic reactions have occurred with atrial and ventricular conduction depression and patients with hypotension and ventricular fibrillation
- Monitor BP, ECG, respiratory function continuously during and for 20 minutes after loading dose
- Monitor for signs/symptoms of depression and behaviour changes
Cautions: Use cautiously in
- Renal impairment
- Hepatic impairment
- Cardiac disease
- Hypotension
- Myocardial insufficiency
- Diabetes mellitus
- Thyroid disorder
- Depression
- History of depression
- Pregnancy
- Porphyria
- Alcohol use
- Avoid abrupt withdrawal
- HLA-B*1502-positive
- Geriatric population
Pregnancy Category:D
Breastfeeding: Phenytoin is excreted in breastmilk in low levels. Thus amounts ingested by the infant are small and usually would cause no difficulties in breastfed infants if used alone, except for rare idiosyncratic reactions. Combination therapy with sedating anticonvulsants may cause sedation or withdrawal reactions. This information is based upon LactMed database (available at http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT last accessed 17 December 2009). This drug may induce methemoglobinemia based upon data from AAP Policy Guidelines (available at http://aappolicy.aappublications.org/cgi/content/full/pediatrics;108/3/776 last accessed 12 April 2011). According to manufacturer's data infant breast feeding is not recommended for women taking this drug as phenytoin appears to be secreted in low concentrations in human milk.
US Trade Name(s)
US Availability
phenytoin (generic)
- INJ: 50 mg/mL (2, 5 mL vials)
- INJ: 50 mg/mL (2, 5 mL amp)
Canadian Trade Name(s)
Canadian Availability
phenytoin (generic)
Tremytoine
UK Trade Name(s)
- Epanutin Ready-Mixed Parenteral
UK Availability
phenytoin (generic)
- INJ: 50 mg/mL (5 mL amp, vial)
Epanutin Ready-Mixed Parenteral
Australian Trade Name(s)
Australian Availability
phenytoin (generic)
- INJ: 100 mg/2 mL
- INJ: 250 mg/5 mL
[Outline]