Anticonvulsant levels and reloading: Difference between revisions

 
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== Background ==
==Background==
*IV load can be performed with phenobarbital, phenytoin, valproate, levetiracetam
*IV load can be performed with [[phenobarbital]], [[phenytoin]], [[valproate]], [[levetiracetam]]
*Oral loading can be spread over day or more to avoid GI upset
*Oral loading can be spread over day or more to avoid GI upset
*May use IV vs PO reload at physican discretion<ref name="ACEP">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>


=== Dose ===
==Initial Loading<ref name="ACEP"></ref>==
Dose (mg) = ideal body weight (kg) X Vd X [desired level - current level (mcg/mL)]
{|class="wikitable"
|'''[[Anticonvulsant]] (brand name)'''
|'''PO Loading Dose'''
|'''IV Loading Dose'''
|-
| [[Carbamazepine]] (Tegretol)
|8mg/kg suspension in single oral load
|NA
|-
| [[Gabapentin]] (Neurontin)
|900mg/day oral (300mg tid) for 3 days
|NA
|-
| [[Lamotrigine]] (Lamictal)
|6.5mg/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
|NA
|-
| [[Levetiracetam]] (Keppra)
|1,500mg oral load
|1,000-1,500 mg IV
|-
| [[Phenytoin]] (Dilantin)
|20mg/kg divided in maximum doses of 400mg every 2 hours
|18mg/kg (max rate of 50mg/min)
|-
|[[Fosphenytoin]] (Cerebyx)
|NA
|18 PE/kg IV (max rate of 150 PE/min)
|-
| [[Valproate]] (Depacon)
|NA
|Up to 30mg/kg IV (max rate of 10mg/kg/min)
|}
 
==Reloading==
*'''Dose (mg) = [[ideal body weight estimation|ideal body weight]] (kg) X Vd X [desired level - current level (mcg/mL)]'''


=== Volume of Distribution ===
===Volume of Distribution===


{| style="width: 500px" border="1" cellpadding="1" cellspacing="1"
{| class="wikitable"
|-
|-
| '''Agent<br/>'''
| '''Agent'''
| '''Volume of Distribution<br/>'''
| '''Volume of Distribution'''
| '''Desired Level'''
|-
|-
| Phenytoin (dilantin)  
| Phenytoin (dilantin)  
| 0.8
| 0.8
| 20 mcg/mL
|-
|-
| Carbamazepine (tegretol)
| Carbamazepine (tegretol)
| 0.8
| 0.8
| 12 mcg/mL
|-
|-
| Phenobarbital
| Phenobarbital
| 0.6
| 0.6
| 40 mcg/mL
|-
|-
| Valproate (depakote)
| Valproate (depakote)
| 0.2
| 0.2
| 100 mcg/mL
|}
|}
=== 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==
===Phenytoin===
====Zero Level of Initial Load====
*IV: 18mg/kg at max rate of 25mg/min
**PO: 18mg/kg as single dose or divided into 3 doses q2hr
*Level above 0 (to avoid over-dosing)
====Subtherapeautic level >0====
Concentration adjusted = (concentration desired - concentration measured) x (0.8 x adjusted body weight)
====Sheiner-Tozer Equation====
*may be needed to correct level in patients with low albumin or abnormal creatinine:
*Corrected level = measured level/[(adjustment x albumin) + 0.1]
*adjustment is 0.2 unless patient has Creatinine clearance <20 then it is 0.1
===Fosphenytoin===
*IV: 18mg PE/kg at 100-150mg/min


==See Also==
==See Also==
*[[Seizure (Peds)]]
*[[Seizure]]
*[[Febrile Seizure]]
*[[Seizure (peds)]]
*[[Dilantin Load]]
*[[Seizure with known seizure disorder]]
*[[Depakote Loading]]
*[[Anticonvulsants]]


==Source==
==References==
DONALDSON 3/08 (from emedicine; Treiman 1997; Bourgeois, 1996)
<references/>


[[Category:Drugs]]
[[Category:Pharmacology]]
[[Category:Neuro]]
[[Category:Neurology]]

Latest revision as of 03:59, 8 March 2021

Background

Initial Loading[1]

Anticonvulsant (brand name) PO Loading Dose IV Loading Dose
Carbamazepine (Tegretol) 8mg/kg suspension in single oral load NA
Gabapentin (Neurontin) 900mg/day oral (300mg tid) for 3 days NA
Lamotrigine (Lamictal) 6.5mg/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 NA
Levetiracetam (Keppra) 1,500mg oral load 1,000-1,500 mg IV
Phenytoin (Dilantin) 20mg/kg divided in maximum doses of 400mg every 2 hours 18mg/kg (max rate of 50mg/min)
Fosphenytoin (Cerebyx) NA 18 PE/kg IV (max rate of 150 PE/min)
Valproate (Depacon) NA Up to 30mg/kg IV (max rate of 10mg/kg/min)

Reloading

Volume of Distribution

Agent Volume of Distribution Desired Level
Phenytoin (dilantin) 0.8 20 mcg/mL
Carbamazepine (tegretol) 0.8 12 mcg/mL
Phenobarbital 0.6 40 mcg/mL
Valproate (depakote) 0.2 100 mcg/mL

See Also

References

  1. 1.0 1.1 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.