Which neurotransmitters does Oxcarbazepine (anticonvulsant medication) increase?

Neurotransmitter Effects of Oxcarbazepine

Oxcarbazepine primarily works by blocking voltage-gated sodium channels and inhibiting the release of excitatory neurotransmitters, particularly glutamate, while having minimal effect on inhibitory neurotransmitters like GABA. 1

Primary Mechanism of Action

Oxcarbazepine functions through several key mechanisms:

1. Sodium Channel Blockade

   • Inhibits voltage-dependent sodium channels, which stabilizes hyperexcited neuronal membranes 2
   • This is the primary mechanism responsible for its anticonvulsant properties

2. Neurotransmitter Effects

   • Glutamate: Significantly inhibits the release of glutamate, the main excitatory neurotransmitter in the brain 1, 3
   • The inhibition occurs at concentrations that correspond to therapeutic plasma levels

3. Effects on Other Neurotransmitters

   • Has similar potency to carbamazepine and lamotrigine in inhibiting the release of:
     • GABA (inhibitory neurotransmitter)
     • Dopamine
     • Serotonin (5-HT)
     • Acetylcholine 1

Comparison with Related Anticonvulsants

Oxcarbazepine shares similar mechanisms with carbamazepine but with some important differences:

• Both drugs inhibit veratrine-induced neurotransmitter release with comparable potency 1
• Oxcarbazepine has a lower propensity for drug interactions compared to older antiepileptic drugs like carbamazepine 4
• In cortical regions, oxcarbazepine can reduce veratridine-induced increases in extracellular glutamate by approximately 50% 3

Clinical Implications

The neurotransmitter effects of oxcarbazepine have several clinical implications:

• Efficacy Profile: Its ability to inhibit glutamate release contributes to its effectiveness in partial and generalized tonic-clonic seizures 4

• Driving Performance: Unlike some other antiseizure medications, oxcarbazepine has less impact on arousal function, which may result in fewer cognitive side effects 5

• Drug Interactions: When used with antiepileptic medications, oxcarbazepine may interact with strong inhibitors of CYP3A or CYP2C8 (like carbamazepine) 5

Important Considerations

While oxcarbazepine does inhibit glutamate release in experimental settings, there are important caveats:

• The drug is markedly less potent in inhibiting electrically stimulated neurotransmitter release (which is more physiological) compared to veratrine-stimulated release 1
• At anticonvulsant doses, oxcarbazepine may not completely suppress the normal ongoing release of glutamate and aspartate 3
• The inhibition of glutamate release may not be the sole mechanism responsible for its anticonvulsant effects 1, 3

In summary, while oxcarbazepine does affect multiple neurotransmitter systems, its primary effect is on reducing excitatory glutamatergic neurotransmission through sodium channel blockade, with relatively minimal effects on GABAergic inhibitory transmission.