QUESTION: Can we give l-glutamine to a patient taking gabapentin? Or are the effects too neuroexitatory?
ANSWER: Starting with the most important level of information (patients and observed effects) I have easily had over 100 patients where we co administered l-glutamine and gabapentin and have not had any experience obvious changes in either the desired effect of the gabapentin nor the l-glutamine. Additionally none experienced any changes in baseline neuroexcitatory activity. Aside from conjectural data (i.e. a few hospital based “don’t take this with that” type websites) the basic science and animal data also is reasonably clear that (if anything) the effects of these two substances may actually be synergistic.
That is outlined here: Branch Chain Aminotransferase isoenzymes (BCAT): Gabapentin competitively inhibits the cytosolic version of BCAT (BCATc – found in cerebrum, placenta and ovary) but not the mitochondrial (body wide BCATm) version. This was an original postulate that gabapentin may reduce glutamate levels by an augmented catabolic pathway in the cytosol. [PMID 9681479] Other authors confirmed this effect of gabapentin as well as showing that it actually decreases synthesis of glutamate in the CNS. [PMID 8565962] A decade or so later it was shown that gabapentin has no effect on cellular glutamine or GABA levels but does indeed decrease glutamate levels. [PMID12810343]. From all of this I am convinced if anything the two agents are neutral in clinical effect or potentially synergistic.