Direct interaction of taurine with the NMDA glutamate receptor subtype via multiple mechanisms.

Taurine has neuroprotective capabilities against glutamate-induced excitotoxicity through several identified mechanisms including opening of the Cl(-)channel associated with GABA(A)and glycine receptors, or a distinct Cl(-)channel. No existing work has however shown a direct interaction of taurine with the glutamate NMDA receptor. Here we demonstrate such direct interactions using electrophysiological and receptor binding techniques on rat medial prefrontal cortical (mPFC) slices and well-washed rat cortical membrane. Electrically evoked field potential responses were recorded in layer 4/5 of mPFC in the presence of picrotoxin to prevent opening of Cl(-)channels gated by GABA or taurine. Applied taurine markedly diminished evoked-response amplitude at the peak and latter phases of the response. These phases were predominantly sensitive to the NMDA antagonist, MK-801, but not the AMPA/kainate receptor antagonist CNQX. Furthermore, this taurine effect was blocked by APV pretreatment. Taurine (0.1 mM) decreased spermine-induced enhancement of specific ((3)H) MK-801 binding to rat cortical membrane in the presence of glycine, though it was ineffective in the absence of spermine. Our preliminary work shows that taurine diminished the apparent affinity of NMDA receptor to glycine in the presence of spermine. These results indicate that taurine may directly interact with the NMDA receptor through multiple mechanisms.

Acute Pain Crisis Caused by Tramadol Remdesivir Drug-Drug Interaction.

Drug interactions are common and can affect patient outcomes. Drugs that undergo emergency approval have less preapproval drug testing to identify potential interactions. Tramadol is an effective pain medication prodrug with a complex mechanism of action that requires extensive metabolism. Remdesivir is an antiviral medication given emergency approval to treat hospitalized patients with COVID-19 infections. Remdesivir is also a nucleotide analogue prodrug that undergoes intracellular metabolic conversions to its active metabolite. We discuss the case of a hospitalized patient in the United States diagnosed with COVID-19 pneumonia who developed acute pain crisis secondary to a drug-drug interaction between tramadol and remdesivir, and we propose a possible mechanism of interaction.