Difference between revisions of "Anticonvulsant levels and reloading"

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***Phenobarbital = 40 mcg/mL
 
***Phenobarbital = 40 mcg/mL
  
==Loading==
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==Loading<ref>Seizures ACEP Policy committee . Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department With Seizures. Ann Emerg Med. 2014;63(4):437–447.e15. doi:10.1016/j.annemergmed.2014.01.018.</ref>==
===Phenytoin===
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{|
====Zero Level of Initial Load====
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| align="center" style="background:#f0f0f0;"|'''Drug (With Selected References)'''
*IV: 18mg/kg at max rate of 25mg/min<ref>Osborn HH, Zisfein J, Sparano R. Single-dose oral phenytoin loading. Ann Emerg Med. 1987;16(4):407-12</ref>
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| align="center" style="background:#f0f0f0;"|'''Loading Dose and Route of Administration'''
**PO: 18mg/kg as single dose or divided into 3 doses q2hr<ref>Ratanakorn D, Kaojarern S, Phuapradit P, Mokkhavesa C. Single oral loading dose of phenytoin: a pharmacokinetics study. J Neurol Sci. 1997;147(1):89-92</ref>
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|-
 
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| Carbamazepine Tegretol||8 mg/kg oral suspension, single oral load; IV not available
====Subtherapeautic level >0====
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|-
Concentration adjusted = (concentration desired - concentration measured) x (0.8 x adjusted body weight)
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| Gabapentin (Neurontin) ||900 mg/day oral (300 mg tid) for 3 days; IV not available
 
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|-
====Sheiner-Tozer Equation====
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| Lacosamide (Vimpat) ||Oral and IV formulations available and safe; loading dosages not studied
*may be needed to correct level in patients with low albumin or abnormal creatinine<ref>Martin E, Tozer TN, Sheiner LB, Riegelman S. The clinical pharmacokinetics of phenytoin. J Pharmacokinet Biopharm. 1977 Dec;5(6):579-96.</ref>
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|-
*Corrected level = measured level/[(adjustment x albumin) + 0.1]
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| Lamotrigine (Lamicta)l ||6.5 mg/kg single oral load if on lamotrigine for >6 mo without a history of rash or intolerance in the past and only off lamotrigine for <5 days; IV not available
*adjustment is 0.2 unless patient has Creatinine clearance <20 then it is 0.1
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|-
 
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| Levetiracetam (Keppra) ||1,500 mg oral load; rapid IV loading safe and well tolerated in doses up to 60 mg/kg
===Fosphenytoin===
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|-
*IV: 18mg PE/kg at 100-150mg/min
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| Phenytoin (Dilantin) ||20 mg/kg divided in maximum doses of 400 mg every 2 h orally, or 18 mg/kg IV at maximum rate of 50 mg/min
 
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|-
===Dapakote===
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| Fosphenytoin (Cerebyx) ||18 PE/kg IV at maximum rate of 150 PE/min; IM administration possible
====Subtherapeutic level > 0====
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|-
*(100-level) .25 x wt
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| Valproate (Depacon) ||Up to 30 mg/kg IV at max rate of 10 mg/kg/min IV
*give over 1 hr
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|}
  
 
==See Also==
 
==See Also==

Revision as of 22:28, 20 April 2014

Background

  • IV load can be performed with phenobarbital, phenytoin, valproate, levetiracetam
  • Oral loading can be spread over day or more to avoid GI upset

Dose

Dose (mg) = ideal body weight (kg) X Vd X [desired level - current level (mcg/mL)]

Volume of Distribution

Agent
Volume of Distribution
Phenytoin (dilantin) 0.8
Carbamazepine (tegretol) 0.8
Phenobarbital 0.6
Valproate (depakote) 0.2

Desired Level

  • Pt's optimal level = desired level
    • If optimal level unknown target upper end of therapeutic range:
      • Phenytoin = 20 mcg/mL
      • Valproate = 100 mcg/mL
      • Phenobarbital = 40 mcg/mL

Loading[1]

Drug (With Selected References) Loading Dose and Route of Administration
Carbamazepine Tegretol 8 mg/kg oral suspension, single oral load; IV not available
Gabapentin (Neurontin) 900 mg/day oral (300 mg tid) for 3 days; IV not available
Lacosamide (Vimpat) Oral and IV formulations available and safe; loading dosages not studied
Lamotrigine (Lamicta)l 6.5 mg/kg single oral load if on lamotrigine for >6 mo without a history of rash or intolerance in the past and only off lamotrigine for <5 days; IV not available
Levetiracetam (Keppra) 1,500 mg oral load; rapid IV loading safe and well tolerated in doses up to 60 mg/kg
Phenytoin (Dilantin) 20 mg/kg divided in maximum doses of 400 mg every 2 h orally, or 18 mg/kg IV at maximum rate of 50 mg/min
Fosphenytoin (Cerebyx) 18 PE/kg IV at maximum rate of 150 PE/min; IM administration possible
Valproate (Depacon) Up to 30 mg/kg IV at max rate of 10 mg/kg/min IV

See Also

Source

  1. Seizures ACEP Policy committee . Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department With Seizures. Ann Emerg Med. 2014;63(4):437–447.e15. doi:10.1016/j.annemergmed.2014.01.018.