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I have in my notes that:

  • Carbamazepinum increases threshold for glutamate
  • Lamotriginum delays release of glutamic acid

I would like to simplify these sentences into a single line. I would like to know if it would be correct to say the following:

  • both Carbamazepinum and Lamotriginum increase glutamate threshold?
  • "both affect glutamate function" should at least be correct

Do both Carbamazepinum and Lamotriginum increase glutamate threshold?


Characterizing those drugs.

A = group, B = mechanism of action and C = indications.

  1. Carbamazepinum A. Anticonvulsant, antiepileptic.
    B. Block Na+ ion channels and inhibit glutamatergic neurotransmission. Inhibit sustained repetitive neuronal firing. C. 1st line of Epilepsy grand mall seizures, bipolar disorder, trigeminal neuralgia.

  2. Lamotriginum A. Unique antiepileptic. B. Block Na+ ion channels and inhibit glutamatergic neurotransmission. Inhibit sustained repetitive neuronal firing. C. 1st line Epilepsy - generalized, partial and absence - all types. Bipolar disorder - depression stage. Neuropathy.

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Short answer
Both carbamazepine and lamotrigine are listed as Na+ channel blockers. Carbamezipine's action is mainly associated with inhibition of postsynaptic neural activity, while lamotrigine is thought to inhibit glutamate release. Given that glutamate is the principal excitatory neurotransmitter in the brain, and if you insist of using a one-liner I would go for:

Both lamotrigin and carbamazepine can be said to inhibit glutatamatergic neurotransmission, albeit carbamezipine does so in a non-specific way.

Background
My two most beloved drugs in one question!

First off, this answer is formulated from the perspective of both drugs being used as anticonvulsants in generalized tonic-clonic epilepsies. As anti-epileptics, Both lamotrigine (Lamictal) and carbamezipine (Tegretol) are listed as Na+-channel blockers.

Carbamezipine does so quite specifically, and it inhibits sustained repetitive firing by blocking sodium channels. It does so in a very clever way, as it only binds to Na+-channels of rapidly firing neurons, which is exactly what makes it a good anti-convulsant (Courtney & Etter, 1983). It also is believed to have anticholinergic, central antidiuretic, antiarrhythmic, muscle relaxant, antidepressant (possibly through blockade of norepinephrine release), sedative, and neuromuscular-blocking properties (Drug bank). Hence, your note that it increases the threshold for glutamate is true in the sense that it is likely to increase the firing threshold of glutamate-activated neurons.

However, note that carbamezipine (nor lamotrigine) does not increase the threshold for glutamate - glutamate has no threshold and hence it cannot be raised. It is incorrect word use.

Lamotrigine is also listed as a Na+-channel blocker, but the exact mechanism(s) behind its anti-convulsive and mood-stabilizing effects are unknown. In vitro pharmacological studies suggest that lamotrigine's inhibiting effects on voltage-sensitive Na+ and/or Ca2+ channels stabilizes neuronal membranes and consequently modulates presynaptic transmitter release of excitatory amino acids (e.g., glutamate and aspartate). It has also been shown to enhance K+ currents and GABA-ergic inhibition (Coulter, 1997). Hence, your note that it decreases glutamate release is correct.

References
Coulter, J Child Neurol (1997); 12: S2-9
Courtney & Etter, Eur J Pharmac (1983); 88: 1-9.

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    $\begingroup$ It says it may involve GABA A/B in the mechanism of action here pubchem.ncbi.nlm.nih.gov/compound/… What do you think? $\endgroup$ – Léo Léopold Hertz 준영 May 27 '15 at 9:51
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    $\begingroup$ In lamotrigine, only in vitro studies about GABA here pubchem.ncbi.nlm.nih.gov/compound/… The exact mechanisms of both these systems are not known. How would summarize this? $\endgroup$ – Léo Léopold Hertz 준영 May 27 '15 at 9:54
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    $\begingroup$ I think the question now is: what disease are you looking at? In my answer, I assumed a focus on epilepsy, since the combination of CBZ and lamotrigine is a very successful one. The GABA effect listed is under neuralgia. Both drugs are 'dirty' drugs and will affect many many systems. The question becomes in which context you are comparing them. Again, in my answer, I reasoned mostly from the anti-convulsive perspective. $\endgroup$ – AliceD May 27 '15 at 9:54
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    $\begingroup$ Again, I wouldn't focus on GABA when talking anti-convulsive therapy. $\endgroup$ – AliceD May 27 '15 at 9:55
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    $\begingroup$ GABA drugs are contra-indicative for generalized tonic-clonic seizures. $\endgroup$ – AliceD May 27 '15 at 9:56

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