PK exam 1

digoxin indications

digoxin indications

inotropic support for HF

Rate control A fib

digoxin dosing

0.125-0.25 mg qd

digoxin TPR

0.5-1 mcg/L for HF

1-2 mcg/L for a fib

digoxin ADR

gi effects

CV: irregular heartbeat, ekg changes, hyperkalemia

visual: blurred vision, color changes, yellow halos

digoxin half life

2 days (normal renal)

4-6 days (no kidney)

hypothyroid with digoxin

high TSH decrease by 30%

hyperthyroid with digoxin

increase by 30%

amiodarone use with digoxin

decrease digoxin 50%

verapamil with digoxin

decrease digoxin 25%

quinidine with digoxin

decrease digoxin 30%

what affects the digoxin clearance

heart failure

what is the usual dosing interval for digoxin

1 day

when to accurately get a sample for digoxin levels with and without loading dose

w/out loading = 3-5 days after

w/ loading = 4 hours after IV, 6 hours after PO

when would you use loading dose for digoxin

AF not HF

Digoxin reversal agents

binds to all digoxin and clears from the body but may falsely elevate measured digoxin levels

Digifab dosing administration

dosing occurs if acute/chronic overdose and if dose is known or not

lidocaine indication

v. arrhythmias

lidocaine dosing for arrhythmia

bolus 1-1.5 mg/kg then infusion of 1-4 mg/min

lidocaine TPR

1-5 mg/L

ADR range for lidocain

minor cns effects 3-5 mg/L

seizures > 9 mg/L

lidocaine sampling time

4-8 hours after beginning of therapy

lidocaine PK is affected by

HF

Medications

Illness

Liver dysfunction

Trauma

first generation AED

CBZ PHT Valproic acid

Second generation AED

Levetiracetam

Lamotrigine

3rd generation AED

lacosamide

Absorption of PHT

low PO

which AED can be given IV

PHT

fosphenytoin

levetiracetam

lacosamide

cbz (discontinued)

loading

maintenance dose of phenytoin

20mg/kg MAX 1500

300 mg po qhs

loading dose

maintenance dose of fosphenytoin

20 PE/kg MAX 1500

none

loading dose

maintenance dose of levetiracetam

60 mg/kg MAX 4500

1000-1500 mg BID

solubility of phenytoin

insoluble therefore dissolved in PEG

phenytoin will precipitate out so must use within 1 hour

oral solutions phenytoin

tube feedings should be stopped 2 hours before/after administration of phenytoin (causes decreased absorption)

what level of phenytoin does TDM measure

trough levels at ss

ADR phenytoin

purple glove syndrome

severe hypotension

cardiac arrhythmia

peg specific:

vein extravasation and cardiotoxicity from fast administration

prevention of phenytoin ADR

slow IV not to exceed 50mg/min

prevention of fosphenytoin ADR

slow IV not to exceed 150 mg/min

what percent of phenytoin is protein bound

90%

what is low protein status

less < 90% protein binding

what conditions cause low protein state

Critically Ill (head trauma, burns)

Hypoalbuminemia (malnutrition)

Elderly

Renal dysfunction

AED inducers of pheytoin

CBZ (induce phenytoin CL)

Lamotrigine (PHT increase CL)

AED inhibitors phenytoin

Valproic acid (dec CL PHT)

elimination of phenytoin

non linear

which AED requires renal dose adjustment

levetiracetam

what should you increase phenytoin by to get patient to TR

if dose pht > 300 increase 30 mg

if dose pht < 300 increase 100 mg