Dilantin
Dilantin® (Phenytoin)
Adult
Ex. head injury
dilantin 750 mg in 0.9%NSS 100 cc iv drip 30 min-1 hr (not rapid 50mg/min)
then 250 mg iv q 8
dose 15-20 mg loading then maintenance 300 mg oral /day
Ex. seizure cap 100 mg
dilantin 6 cap stat then 3 cap od hs
ปัจจุบันให้ 3-3-2 q 2hr น้ำหนักมากให้ 4-3-3 ห่าง q 2 hr
Pediatric
Dose 5-8 mg/kg/day cap 100 mg, tab 50 mg
dose 15-20 mg loading mg/kg/loading
then maintenance 5-10 mg/kg/day q 8
Precuation
Don't use IM ยาจะตกตะกอนในกล้ามเนื้อ
ไม่ละลายใน 5%DW
ref.
http://www.pharmyaring.com/pic/p_120424133754.pdf
Dilantin® (Phenytoin)
Loading Dose (IV): 10 - 20 mg/kg. Maximum rate: 50 mg/min. Recommended infusion rate for adults: 40-50 mg/min. Elderly (>65): Recommended infusion rate: 20-25 mg/min.
Oral loading:
Give in 3 to 4 divided doses at q2h intervals. 3-3-2q2hr
(Divided doses increase bioavailability as well as decrease potential for GI side effects such as N&V). The [[javascript:alert("For example a 1 gram oral load could be given by first giving 400mg x1 then 300mg po x2. Each dose is separated by 2 hours.");|maximum single oral dose should not exceed 400 mg]] in order to minimize GI side effects and also increase absorption (decrease likelihood of concretions). Maintenance: 4-6 mg/kg/day given in 2 to 3 divided doses. Equation used to estimate the dose required to increase current level to normal range if sub-therapeutic: [ 0.7 x IBW x (15 - current level)]
.
Oral suspension administration: Shake well prior to use. Divide the daily dose of phenytoin and withhold the administration of nutritional supplements for 1-2 hours before and after each phenytoin dose.
Sampling: 18 to 24 hours after the loading dose, and then every 5 to 7 days to assess trend.
Average time to steady state: 10-14 days. Half-life: 7 to 42 hours (average = 24 hours).
Conversion to once daily dosing: Consider only after a divided dose regimen on extended phenytoin capsules is established. (Only extended release Dilantin caps are recommended for once daily administration.) A patient should never receive a once daily dose of elixir or injection as maintenance.
When do you start the maintenance dose? The maintenance dose is started 18-24 hours after the loading dose.
Capsules/injection= 92% phenytoin (sodium salt). Elixir/tabs=100% phenytoin.
Equation used to estimate the dose required to increase current level to normal range if subtherapeutic: = [0.7 x IBW x (15 - current level) ] / 0.92* * (if capsules/injection used)
Adjusted phenytoin concentration if low serum albumin
= measured total concentration / [ (0.2 x albumin) + 0.1].
Renal failure:
Cadjusted = Cmeasured / [ (0.1 x albumin) + 0.1) ]
Reference