Read Mosby's 2014 Nursing Drug Reference Online
Authors: Linda Skidmore-Roth
Mosby's 2014 Nursing Drug Reference (319 page)
(fen′i-toh-in)
Dilantin, Dilantin Infatabs, Phenytek
Func. class.:
Anticonvulsant; antidysrhythmic (IB)
Chem. class.:
Hydantoin
Inhibits spread of seizure activity in motor cortex by altering ion transport; increases AV conduction
Generalized tonic-clonic seizures; status epilepticus; nonepileptic seizures associated with Reye’s syndrome or after head trauma; Bell’s palsy, complex partial seizures
Unlabeled uses:
Migraines, diabetic neuropathy, neuropathic pain, paroxysmal atrial tachycardia, ventricular tachycardia
Pregnancy (D), hypersensitivity, psychiatric condition, bradycardia, SA and AV block, Stokes-Adams syndrome, hepatic failure, acute intermittent porphyria
Precautions:
Geriatric patients, allergies, renal/hepatic disease, petit mal seizures, hypotension, myocardial insufficiency, Asian patients positive for HLA-B1502
Black Box Warning:
IV use
Calculator
• Adult:
PO
15-20 mg/kg (ext rel) in 3-4 divided doses given q2hr or 400 mg then 300 mg q2hr × 2 doses; maintenance 4-7 mg/kg/day;
IV
15-20 mg/kg, max 25-50 mg/min, then 100 mg q6-8hr
• Child:
PO
5 mg/kg/day in 2-3 divided doses, maintenance 4-8 mg/kg/day in 2-3 divided doses, max 300 mg/day;
IV
15-20 mg/kg at 1-3 mg/kg/min
• Adult:
IV
10-15 mg/kg, max 25-50 mg/min, may give 100 mg q6-8hr thereafter
• Child:
IV
15-20 mg/kg, max in divided doses 1-3 mg/kg/min
• Adult:
PO
Loading dose 1 g divided over 24 hr then 500 mg/day × 2 days;
IV
250 mg over 5 min until dysrhythmias subside or until 1 g is given or 100 mg q15min until dysrhythmias subside or until 1 g is given
• Child:
PO
3-8 mg/kg or 250 mg/m
2
/day as single dose or 2 divided doses;
IV
3-8 mg/kg over several min or 250 mg/m
2
/day as single dose or 2 divided doses
•
Do not use loading dose if CCr <10 ml/min or hepatic failure
• Adult:
PO
300 mg/day in divided doses
• Adult:
PO
200-400 mg/day
Available forms:
Susp 25 mg/5 ml; chewable tabs 50 mg; inj 50 mg/ml; ext rel caps 100, 200, 300 mg; prompt rel caps 100 mg
•
Do not interchange chewable product with caps, not equivalent; only ext rel caps to be used for once-a-day dosing
•
Oral susp:
shake well before each dose given via G tube/NG tube; dilute susp prior to administration; flush tube with 20 ml water after dose, hold tube feedings 1 hr before and 1 hr after dose
•
Allow 7-10 days between dosage changes
•
Divided PO doses with or after meals to decrease adverse effects
•
2 hr before or after antacid, enteral feeding
Black Box Warning:
Give undiluted at ≤50 mg/min (adult) 1-3 mg/kg/min (neonates), monitor for CV reactions
Black Box Warning:
Dilute dose in NS to ≤6.7 mg/ml, complete inf within 1 hr of preparation, use 0.22 or 0.45 micron in-line particulate final filter between IV catheter and tubing, flush IV line or catheter with NS before and after use, give at ≤50 mg/min (adult), 0.5-1 mg/kg/min (child, infant, neonate)
Additive compatibilities:
Do not admix
Y-site compatibilities:
CISplatin, foscarnet, temocillin
CNS:
Drowsiness, dizziness, insomnia, paresthesias, depression,
suicidal tendencies,
aggression, headache, confusion, slurred speech, peripheral neuropathy
CV:
Hypotension,
ventricular fibrillation
EENT:
Nystagmus, diplopia, blurred vision
ENDO:
Diabetes insipidus
GI:
Nausea, vomiting, constipation, anorexia, weight loss,
hepatitis,
jaundice, gingival hyperplasia
GU:
Nephritis,
urine discoloration
HEMA:
Agranulocytosis, leukopenia, aplastic anemia, thrombocytopenia, megaloblastic anemia
INTEG:
Rash,
lupus erythematosus, Stevens-Johnson syndrome,
hirsutism,
toxic epidermal necrolysis
SYST:
Hypocalcemia,
purple glove syndrome (IV), DRESS, anaphylaxis
Metabolized by liver, excreted by kidneys, protein binding 90%-95%, half-life 7-42 hr, dose dependent
PO:
Onset 2-24 hr, peak 11/2-21/2 hr, duration 6-12 hr
PO-ER:
Onset 2-24 hr, peak 4-12 hr, duration 12-36 hr
IV:
Onset 1-2 hr, duration 12-24 hr
•
Do not use with delavirdine, decreased response, resistance
Increase:
phenytoin effect—benzodiazepines, cimetidine, tricyclics, salicylates, valproate, cycloSERINE, diazepam, chloramphenicol, disulfiram, alcohol, amiodarone, sulfonamides, FLUoxetine, gabapentin, H
2
antagonists, azole antifungals, estrogens, succinamides, phenothiazines, methylphenidate, felbamate, trazodone
Decrease:
phenytoin effects—alcohol (chronic use), antacids, barbiturates, carBAMazepine, rifampin, calcium (high dose), folic acid
Enteral tube feeding:
may decrease absorption of oral product; do not use enteral feedings 2 hr before or 2 hr after dose
Increase:
glucose, alk phos, GGT
Decrease:
dexamethasone, metyrapone test serum, PBI, urinary steroids
Phenytoin hypersensitivity syndrome
3-12 wk after start of treatment: rash, temp, lymphadenopathy; may cause hepatotoxicity, renal failure, rhabdomyolysis
Serious skin disorders:
for beginning rash that may lead to Stevens-Johnson syndrome or toxic epidermal necrolysis; phenytoin should not be used again; may occur more often among Asian patients with HLA-B 1502
Purple glove syndrome
with IV use
•
Phenytoin level: toxic level 30-50 mcg/ml, therapeutic level: 7.5-20 mcg/ml; wait ≥1 wk to draw levels
•
Seizures:
duration, type, intensity, precipitating factors; obtain EEG periodically, monitor therapeutic level
•
Blood studies: CBC, platelets q2wk until stabilized, then monthly × 12, then q3mo; discontinue product if neutrophils <1600/mm
3
; renal function: albumin conc; folic acid levels, LFTs
Mental status: mood, sensorium, affect, memory (long, short), suicidal thoughts/behaviors
•
Respiratory depression:
rate, depth, character
•
Blood dyscrasias:
fever, sore throat, bruising, rash, jaundice
•
Therapeutic response; decrease in severity of seizures, ventricular dysrhythmias
•
That, if diabetic, blood glucose should be monitored
•
That urine may turn pink
• Not to discontinue product abruptly because seizures may occur
•
Oral hygiene:
about the proper brushing of teeth using a soft toothbrush, flossing to prevent gingival hyperplasia; about the need to see dentist frequently
•
To avoid hazardous activities until stabilized on product
•
To carry emergency ID stating product use
•
That heavy use of alcohol may diminish effect of product; to avoid OTC medications
•
Not to change brands or forms once stabilized on therapy because brands may vary
•
Not to use antacids within 2 hr of product
• To use nonhormonal contraception; to notify prescriber if pregnancy is planned or suspected, pregnancy (D)
• To notify prescriber of unusual bleeding, bruising, petechiae (bleeding), clay-colored stools, abdominal pain, dark urine, yellowing of skin or eyes (hepatotoxicity); slurred speech, headache, drowsiness
Canada only Side effects:
italics
= common;
bold
= life-threatening Nurse Alert