An Update on Stiripentol Mechanisms of Action: A Narrative Review

Stiripentol (Diacomit®) (STP) is an orally active antiseizure medication (ASM) indicated as adjunctive therapy, for the treatment of seizures associated with Dravet syndrome (DS), a severe form of childhood epilepsy, in conjunction with clobazam and, in some regions valproic acid. Since the discovery of STP, several mechanisms of action (MoA) have been described that may explain its specific effect on seizures associated with DS. STP is mainly considered as a potentiator of gamma-aminobutyric acid (GABA) neurotransmission: (i) via uptake blockade, (ii) inhibition of degradation, but also (iii) as a positive allosteric modulator of GABAA receptors, especially those containing α3 and δ subunits. Blockade of voltage-gated sodium and T-type calcium channels, which is classically associated with anticonvulsant and neuroprotective properties, has also been demonstrated for STP. Finally, several studies indicate that STP could regulate glucose energy metabolism and inhibit lactate dehydrogenase. STP is also an inhibitor of several cytochrome P450 enzymes involved in the metabolism of other ASMs, contributing to boost their anticonvulsant efficacy as add-on therapy. These different MoAs involved in treatment of DS and recent data suggest a potential for STP to treat other neurological or non-neurological diseases.

Microorganisms linked to inflammatory bowel disease-associated dysbiosis differentially impact host physiology in gnotobiotic mice

Studying host-microbiota interactions are fundamental to understanding the mechanisms involved in intestinal homeostasis and inflammation. In this work, we analyzed these interactions in mice that were mono-associated with six microorganisms that are representative of inflammatory bowel disease (IBD)-associated dysbiosis: the bacteria Bacteroides thetaiotaomicron, adhesive-invasive Escherichia coli (AIEC), Ruminococcus gnavus and Roseburia intestinalis; a yeast used as a probiotic drug, Saccharomyces boulardii CNCM I-745; and another yeast, Candida albicans. Extensive ex vivo analyses including colon transcriptomics, histology, immune response, bile acid metabolism and short-chain fatty acid production were studied. We showed that B. thetaiotaomicron had the highest impact on the immune system because it was almost able to recapitulate the effects of the entire conventional microbiota and notably induced Treg pathways. Furthermore, these analyses uncovered the effects of E. coli AIEC LF82 on indoleamine 2,3-dioxygenase expression and of S. boulardii CNCM I-745 on angiogenesis. These results were confirmed in vitro in human cell lines. Finally, our results suggested that R. gnavus has major effects on metabolism, and notably on tryptophan metabolism. This work therefore reveals that microorganisms with a potential role in intestinal homeostasis and inflammation have specific impacts on the host, and it suggests several tracks to follow to understand intestinal homeostasis and IBD pathogenesis better, providing new insights to identify novel therapeutic targets.

Saccharomyces boulardii does not prevent relapse of Crohn's disease

BACKGROUND & AIMS

Saccharomyces boulardii is a probiotic yeast that has been shown to have beneficial effects on the intestinal epithelial barrier and digestive immune system. There is preliminary evidence that S boulardii could be used to treat patients with Crohn's disease (CD). We performed a randomized, placebo-controlled trial to evaluate the effects of S boulardii in patients with CD who underwent remission during therapy with steroids or aminosalicylates.

METHODS

We performed a prospective study of 165 patients who achieved remission after treatment with steroids or salicylates; they were randomly assigned to groups given S boulardii (1 g/day) or placebo for 52 weeks. The primary end point was the percentage of patients in remission at week 52. Time to relapse, Crohn's disease activity index scores, and changes in parameters of inflammation were secondary end points.

RESULTS

CD relapsed in 80 patients, 38 in the S boulardii group (47.5%) and 42 in the placebo group (53.2%, a nonsignificant difference). The median time to relapse did not differ significantly between patients given S boulardii (40.7 weeks) vs placebo (39.0 weeks). There were no significant differences between groups in mean Crohn's disease activity index scores or erythrocyte sedimentation rates or in median levels of C-reactive protein. In a post hoc analysis, nonsmokers given S boulardii were less likely to experience a relapse of CD than nonsmokers given placebo, but this finding requires confirmation.

CONCLUSIONS

Although the probiotic yeast S boulardii is safe and well tolerated, it does not appear to have any beneficial effects for patients with CD in remission after steroid or salicylate therapies.

Nefopam pharmacokinetics in patients with end-stage renal disease

BACKGROUND

Treatment of intense postoperative pain in patients with end-stage renal disease (ESRD) is a recurrent problem for anesthesiologists because of the risk of accumulation of numerous molecules and their metabolites. Nefopam is a potent analgesic metabolized by the liver and weakly eliminated intact in urine that may offer advantages for use in patients with ESRD because it lacks respiratory-depressive effects. However, the effects of renal failure on nefopam disposition have never been investigated.

METHODS

We studied 12 ESRD patients (creatinine clearance < 20 mL/min, mean age 57 ± 13 years) having surgery under general anesthesia to create or repair an arteriovenous fistula. Postoperatively, after complete recovery from anesthesia, each patient received a single 20-mg dose of nefopam IV over 30 minutes. Nefopam and desmethyl-nefopam concentrations in plasma samples obtained over 48 hours were determined by liquid chromatography-tandem mass spectrometry. The pharmacokinetic parameter values obtained were compared with those of 12 healthy 50- to 60-year-old volunteers who also received a single 20-mg nefopam infusion over 30 minutes using a population pharmacokinetic approach.

RESULTS

Healthy volunteers and ESRD patients had comparable demographic characteristics. In comparison with those volunteers, ESRD patients had a lower volume of central compartment (115 and 53 L vs. 264 L for patients not yet hemodialyzed and on chronic hemodialysis, respectively; P < 0.001) and lower mean nefopam clearance (37.0 and 27.3 L/h vs. 52.9 L/h, P < 0.001), resulting in higher mean nefopam peak concentration (121 and 223 ng/mL vs. 61 ng/mL, P < 0.001).

CONCLUSIONS

Nefopam distribution and elimination are altered in patients with ESRD, resulting in heightened exposure. To avoid too-high concentration peaks, it is suggested that the daily nefopam dose be reduced by 50%.

Endotoxemia does not limit energy supply in exercising rat skeletal muscle

Although depletion in high-energy phosphorylated compounds and mitochondrial impairment have been reported in septic skeletal muscle at rest, their impact on energy metabolism has not been documented during exercise. In this study we aimed to investigate strictly gastrocnemius muscle function non-invasively, using magnetic resonance techniques in endotoxemic rats. Endotoxemia was induced by injecting animals intraperitoneally at t(0) and t(0) + 24 h with Klebsiella pneumoniae lipopolysaccharides (at 3 mg kg(-1)). Investigations were performed at t(0) + 48 h during a transcutaneous electrical stimulation protocol consisting of 5.7 min of repeated isometric contractions at a frequency of 3.3 HZ. Endotoxin treatment produced a depletion in basal phosphocreatine content and a pronounced reduction in oxidative adenosine triphosphate (ATP) synthesis capacity, whereas the resting ATP concentration remained unchanged. During the stimulation period, endotoxemia caused a decrease in force-generating capacity that was fully accounted for by the loss of muscle mass. It further induced an acceleration of glycolytic ATP production and an increased accumulation of adenosine diphosphate (ADP, an important mitochondrial regulator) that allowed a near-normal rate of oxidative ATP synthesis. Finally, endotoxemia did not affect the total rate of ATP production or the ATP cost of contraction throughout the whole stimulation period. These data demonstrate that, in an acute septic phase, metabolic alterations in resting muscle do not impact energy supply in exercising muscle, likely as a result of adaptive mechanisms.

Effect of route of administration on the pharmacokinetic behavior of enantiomers of nefopam and desmethylnefopam

Nefopam hydrochloride is a non-narcotic analgesic used parenterally and orally as a racemic mixture for the relief of postoperative pain. However, no information is presently available on the oral kinetics of (+) and (-) nefopam in humans. Also, nefopam is metabolized by N-demethylation but it is not known whether the desmethylnefopam enantiomers (DES1 and DES2) are present in plasma following intravenous (I.V.) or oral administration of parent drug. To address these issues, 24 healthy white male subjects received two treatments using a double-blind, placebo-controlled crossover design: oral administration of 20 mg nefopam hydrochloride solution or a placebo solution on a sugar cube, simultaneously with a continuous infusion of 20 mg nefopam hydrochloride or placebo infusion. A chiral assay using LC-MS was developed for the simultaneous determination of both enantiomers of the parent drug and its metabolite in plasma and urine. Following I.V. administration, the kinetics of (+) and (-) nefopam could be fitted to a bi-exponential equation but exhibited no stereoselectivity. Both enantiomers had large clearances (53.7 and 57.5 L/hr) and volumes of distribution (390 and 381 L) and half-lives around 5 hours. Following oral administration, (+) and (-) nefopam were rapidly absorbed with bioavailabilities of 44% and 42%, respectively, probably due to a first-pass effect. After I.V. administration, the enantiomers of desmethylnefopam exhibited lower concentrations and longer half-lives (20.0 h for DES1 and 25.3 h for DES2) relative to nefopam enantiomers. Following oral administration, desmethylnefopam enantiomers' plasma concentrations peaked earlier and higher than after I.V. administration (P < 0.05). Following I.V. and oral administration, desmethylnefopam enantiomers showed stereoselectivity in AUC and Cmax values. Urinary excretion of parent and metabolite enantiomers was less than 5% of dose. This study shows that desmethylnefopam enantiomers can contribute to the analgesic effect of racemic nefopam only when it is administered orally.