Analgesic Options Using Antiepileptic Medication |…

Analgesic Options Using Antiepileptic Medication

Drug Summary

Source: Burton AW. Internet Journal of Pain, Symptom Control & Palliative Care. 2001;1n2. www.ispub.com/ostia/index.php?xmlFilePath=journals/ijpsp/front.xml.

In the following table, 13 antiepileptic agents that may be considered for long-term pain control are listed with dosage and side effect profile. We hope our readers will find this table convenient and useful. —Michael Rubin, Professor of Clinical Neurology, New York Presbyterian Hospital-Cornell Campus, Assistant Editor, Neurology Alert.

Table: Antiepileptic Drugs for Pain Management
Drug	Mechanism of Action	Side Effects	Maximum*

Carbamazepine	Slows recovery rate of voltage gated Na+ channels	drowsiness, diplopia, unsteadiness aplastic anemia (1:200,000)	1600 mg/d
Phenytoin	Similar to carbamazepine	nausea, diplopia, dizziness, confusion, gingival hyperplasia, Stevens-Johnson syndrome	600 mg/d
Valproic Acid	Similar to carbamazepine, also increases levels of GABA by decreasing degradation	nausea, vomiting, sedation ataxia, rash, alopecia, appetite stimulation elevated transaminases in 40%	60 mg/kg/d
Clonazepam	Enhancement of the GABA-induced increase in chloride conductance	sedation, lethargy, ataxia, dizziness	20 mg/d
Gabapentin	Uncertain, may have its effect at a central voltage dependent L-type Ca++ channel	drowsiness, somnolence, fatigue	3600 mg/d
Pregabalin	gabapentin analog	not yet approved for clinical use
Lamotrigine	Inhibitor of voltage gated Na+ channels; may suppress glutamate release; may inhibit serotonin reuptake	dizziness, diplopia, drowsiness, rash	900 mg/d
Topiramate	Potentiates GABA responses, increasing CNS GABA levels, blocks the AMPA kainate excitatory receptor, weak carbonic anhydrase inhibitor	abnormal thinking, psychotic thinking, delusional	400 mg/d
Oxcarbezapine	Similar to carbamazepine, may modulate voltage activated Ca++ currents	drowsiness, diplopia, unsteadiness	2400 mg/d
Felbamate	Decreases glutamate synthesis, blocks NMDA receptors	rare hepatotoxicity, aplastic anemia	3600 mg/d
Zonisamide	Na+ channel blockade; T-type Ca++ channel blockade; carbonic anhydrase inhibitor		600 mg/d
Tiagabine	GABA reuptake inhibitor; future potential for the treatment of painful conditions		60 mg/d
Vigabatrin	GABA metabolism inhibitor; future potential for the treatment of painful conditions		4000 mg/d

N.B. Only carbamazepine, phenytoin, gabapentin, and lamotrigine have been evaluated in double-blind trials (JAMA.* 1998;280:1837-1842; Pain. 1997; 73:223-230). Always begin with a low dose, preferably at bedtime. Increase gradually until side effects occur. Maximum dose may be exceeded if patient is tolerant. Pain relief may be gradual; wait 4-8 weeks at therapeutic dosage before moving to a different agent.