Pharmacodynamics (or how the DRUG affects the body)

Tuesday, 01 March 2005 13:06


It is thought that they have dual modes of action:

(i)                blockade of sodium channels

(ii)              potentiation of GABAergic neurotransmitter system*

Gabapentin does not appear to act at GABA receptor sites even though it was developed as a GABA analogue.

Hansen ([i]) suggests that allodynia may respond to gabapentin because of an effect on the GABAA receptor which inhibits large afferent (A beta) excitatory input.

Other research([ii]) has shown that gabapentin mimics GABAb receptor activation, but is active independently of the GABA receptor mechanism.

This is borne out clinically by the effect gabapentin has on reducing muscle spasm. Shimoyama et al([iii]) recently concluded from their animal studies that

"The antinociceptive effects of GBP may involve the inhibition of the release of excitatory amino acids from presynaptic terminals."


[ii] Schlicker E, Reimann W, Gothert M Drug Res Gabapentin decreases monoamine release without affecting acetylcholine release in the brain.


[iii] Shimoyama M, Shimoyama N, Hori Y Pain 2000 Apr;85(3):405-14


Gabapentin affects glutamatergic excitatory neurotransmission in the rat dorsal horn.

[iv] Czuczwar SJ Neurol Neurochir Pol 2000;33 Suppl 1:13-20 [GABA-ergic system and antiepileptic drugs].

[v] Teoh H, Fowler LJ, Bowery NG. Neuropharmacol 1995;34:1273-8 Effect of lamotrigine on the electrically-evoked release of amino acids from slices of dorsal horn of the rat spinal cord.