Guidelines for Intravenous Phenytoin Preparation
compatibile in 0.9% normal saline and lacted ringers solution (incompatibile in dextrose)
store at room temperature - will crystalize out when refrigerated
dilute phenytoin in normal saline to final concentration between 1-10mg/ml
use 0.22 micron filter with phenytoin IV to prevent any crystals from getting into IV line
use shortly after diluting phenytoin solution, and discard unused solution after 4 hours
check IV bag periodically for any precipitate formulation
flush IV line with normal saline before and after phenytoin dose
Dilution Guidelines
Phenytoin Dose Mininum Volume (Peripheral Line) Suggested Volume (Central Line)
600-1000mg 100 or 250mg 0.9% normal saline 100ml 0.9% normal saline
301-600mg 100ml 0.9% normal saline 100ml 0.9% normal saline
101-300mg 50ml 0.9% normal saline 50ml 0.9% normal saline
100mg or less 25ml 0.9% normal saline 25ml 0.9% normal saline
Rate Monitor
maximum rate in healthy adults: 50mg/min EKG, HR, and BP at 60 second intervals for first 5 minutes, and every 5 minutes thereafter (up to 15-30 minutes after infusion completed)
in elderly, patients with cardiotoxicity risk factors, hypotensive patients, or patients with infusion associated pain: 25mg/min
watch for cardiac arrhythmias, hypotension, bradycardia, and CNS depression
Managing Adverse Reactions
if hypotension or bradycardia occurs - discontinue infusion and restart at half the initial rate when vital signs return to pre-infusion values also monitor for: albumin, hepatic function, and serum phenytoin
normal serum phenytoin: 10-20mcg/ml (free phenytoin 1-2mcg/ml)
need to adjust for low albumin (because phenytoin binds to albumin)
if patient complains of pain or burning - decrease infusion rate or further dilute infusion (min. 1mg/ml)
use formula for corrected phenytoin: corrected level = observed level / 0.25 X albumin + 0.1
if extravasation occurs - elevate patient's limb, use a cold pack, and if necessary use Wydase (Hyaluronidase):
need to adjust phenytoin rates in patients with severe liver impairment/cirrhosis
add 1ml of normal saline to 150 units vial to make 150 unit/ml concentration, and administer 0.2ml sc/im to the site at the leading edge
currently, phenytoin IVPB is limited to the Emergency Dept. only
services are expected to be expanded to include ICU, CCU, and RICU
Return to Main Index