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* |
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| 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 | |
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| *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. | |||
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