Difference between revisions of "Anticonvulsant levels and reloading"

(Subtherapeautic level >0)
(Reloading)
 
(44 intermediate revisions by 5 users not shown)
Line 1: Line 1:
== 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 15:25, 27 September 2019

Background

  • IV load can be performed with phenobarbital, phenytoin, valproate, levetiracetam
  • Oral loading can be spread over day or more to avoid GI upset
  • May use IV vs PO reload at physican discretion[1]

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.