The Interplay between Liver First-Pass Effect and Lymphatic Absorption of Cannabidiol and its Implications for Cannabidiol Oral Formulations

For highly lipophilic drugs, passage into the intestinal lymphatic system rather than the portal vein following oral administration may represent a major alternative route of delivery into the general circulation. Increasing intestinal lymphatic transport provides an effective strategy to improve oral bioavailability when hepatic first-pass metabolism is a major rate-limiting step hampering access to the systemic circulation after oral dosing. The transfer of orally administered, highly lipid-soluble drugs to the lymphatic system is mediated by their association with chylomicrons, large intestinal lipoproteins that are assembled in the enterocytes in the presence of long-chain triglycerides or long-chain fatty acids. Due to its very high lipophilicity, cannabidiol (CBD) has physicochemical features (e.g. logP = 6.3) consistent with an oral absorption mediated at least in part by transport via the intestinal lymphatic system. CBD also undergoes extensive first-pass hepatic metabolism. Formulation changes favoring diversion of orally absorbed CBD from the portal to the lymphatic circulation pathway can result in reduced first-pass liver metabolism, enhanced oral bioavailability, and reduced intra- and intersubject variability in systemic exposure. In this manuscript, we discuss (1) evidence for CBD undergoing hepatic first-pass liver metabolism and lymphatic absorption to a clinically important extent; (2) the potential interplay between improved oral absorption, diversion of orally absorbed drug to the lymphatic system, and magnitude of presystemic elimination in the liver; and (3) strategies by which innovative chemical and/or pharmaceutical delivery systems of CBD with improved bioavailability could be developed

Propylisopropylacetic acid (PIA), a constitutional isomer of valproic acid, uncompetitively inhibits arachidonic acid acylation by rat acyl-CoA synthetase 4: A potential drug for bipolar disorder

Mood stabilizers used for treating bipolar disorder (BD) selectively downregulate arachidonic acid (AA) turnover (deacylation-reacylation) in brain phospholipids, when given chronically to rats. In vitro studies suggest that one of these, valproic acid (VPA), which is teratogenic, reduces AA turnover by inhibiting the brain acyl-CoA synthetase (Acsl)-4 mediated acylation of AA to AA-CoA. We tested whether non-teratogenic VPA analogues might also inhibit Acsl-4 catalyzed acylation, and thus have potential anti-BD action

Syntheses and Evaluation of Anticonvulsant Activity of Novel Branched Alkyl Carbamates

A novel class of 19 carbamates was synthesized, and their anticonvulsant activity was comparatively evaluated in the rat maximal electroshock (MES) and subcutaneous metrazol (scMet) seizure tests and pilocarpine-induced status epilepticus (SE) model. In spite of the alkyl-carbamates' close structural features, only compounds <b>34</b>, <b>38</b>, and <b>40</b> were active at the MES test. The analogues 2-ethyl-3-methyl-butyl-carbamate (<b>34</b>) and 2-ethyl-3-methyl-pentyl-carbamate (<b>38</b>) also exhibited potent activity in the pilocarpine-SE model 30 min postseizure onset. Extending the aliphatic side chains of homologous carbamates from 7 to 8 (<b>34</b> to <b>35</b>) and from 8 to 9 carbons in the homologues <b>38</b> and <b>43</b> decreased the activity in the pilocarpine-SE model from ED₅₀ = 81 mg/kg (<b>34</b>) to 94 mg/kg (<b>35</b>) and from 96 mg/kg (<b>38</b>) to 114 mg/kg (<b>43</b>), respectively. The most potent carbamate, phenyl-ethyl-carbamate (<b>47</b>) (MES ED₅₀ = 16 mg/kg) contains an aromatic moiety in its structure. Compounds <b>34</b>, <b>38</b>, <b>40</b>, and <b>47</b> offer the optimal efficacy–safety profile and, consequently, are promising candidates for development as new antiepileptics

Novel treatment approaches and pediatric research networks in status epilepticus

This paper contains five contributions which were presented as part of the novel therapies section of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures. These illustrate recent advances being made in the management and therapy of status epilepticus. The five contributions concern: genetic variations in Na + channel genes and their importance in status epilepticus; the European Reference Network for rare and complex epilepsies EpiCARE; the North American Pediatric Status Epilepticus Research Group (pSERG); Fenfluramine as a potential therapy for status epilepticus' and the valproate derivatives, valnoctamide and sec-butylpropylacetamide (SPD), as potential therapies for status epilepticus. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures".status: publishe

Stereoselective pharmacokinetic analysis of valnoctamide in healthy subjects and in patients with epilepsy.

OBJECTIVE: To investigate the pharmacokinetics of the four stereoisomers of valnoctamide, a mild tranquilizer endowed with anticonvulsant properties. METHODS: Racemic valnoctamide, 400 mg, was administered orally to seven healthy subjects and to six patients with epilepsy stabilized with long-term carbamazepine therapy. In the patients with epilepsy, valnoctamide kinetics was also reassessed after 8-day oral dosing at a dosage of 600 mg daily. Plasma samples were assayed by gas chromatography-mass spectrometry with use of a capillary column coated with chiral stationary phase that enabled baseline resolution of the four stereoisomers, designated hereafter as A, B, C, and D (where A and C, together with B and D, represent enantiomeric pairs). RESULTS: In healthy subjects, stereoisomers A, C, and D showed similar kinetics, with an apparent oral clearance (CL/F) of about 4 1/2 L/hr, a half-life (t1/2) of about 10 hours, and an apparent volume of distribution (VSS/F) of about 65 L. However, stereoisomer B showed a much higher clearance (8.7 +/- 0.9 L/hr) and a shorter t1/2 (5.8 hours). For all stereoisomers, CL/F values in patients with epilepsy were about tenfold higher than those found in healthy subjects. Compared with healthy subjects, patients with epilepsy also showed shorter t1/2 values and higher VSS/F values for each of the stereoisomers. After 7-day dosing, CL/F values at steady state were lower than those determined in the same patients after a single dose. CONCLUSIONS: Valnoctamide exhibits enantioselectivity and diastereoselectivity, an observation that may have important practical implications if pharmacodynamic differences between stereoisomers are also found. The observed pharmacokinetic differences between healthy subjects and patients with epilepsy are likely to be related to induction of metabolism of valnoctamide stereoisomers by carbamazepine

Stereoselective Analysis of the Antiseizure Activity of Fenfluramine and Norfenfluramine in Mice: Is <i>l</i>-Norfenfluramine a Better Follow-Up Compound to Racemic-Fenfluramine?

The aim of this study was to investigate the comparative antiseizure activity of the l-enantiomers of d,l-fenfluramine and d,l-norfenfluramine and to evaluate the relationship between their concentration in plasma and brain and anticonvulsant activity. d,l-Fenfluramine, d,l-norfenfluramine and their individual enantiomers were evaluated in the mouse maximal electroshock seizure (MES) test. d,l-Fenfluramine, d,l-norfenfluramine and their individual l-enantiomers were also assessed in the DBA/2 mouse audiogenic seizure model. All compounds were administered intraperitoneally. Brain and plasma concentrations of the test compounds in DBA/2 mice were quantified and correlated with anticonvulsant activity. In the MES test, fenfluramine, norfenfluramine and their enantiomers showed comparable anticonvulsant activity, with ED50 values between 5.1 and 14.8 mg/kg. In the audiogenic seizure model, l-norfenfluramine was 9 times more potent than d,l-fenfluramine and 15 times more potent than l-fenfluramine based on ED50 (1.2 vs. 10.2 and 17.7 mg/kg, respectively). Brain concentrations of all compounds were about 20-fold higher than in plasma. Based on brain EC50 values, l-norfenfluramine was 7 times more potent than d,l-fenfluramine and 13 times more potent than l-fenfluramine (1940 vs. 13,200 and 25,400 ng/g, respectively). EC50 values for metabolically formed d,l-norfenfluramine and l-norfenfluramine were similar to brain EC50 values of the same compounds administered as such, suggesting that, in the audiogenic seizure model, the metabolites were responsible for the antiseizure activity of the parent compounds. Because of the evidence linking d-norfenfluramine to d,l-fenfluramine to cardiovascular and metabolic adverse effects, their l-enantiomers could potentially be safer follow-up compounds to d,l-fenfluramine. We found that, in the models tested, the activity of l-fenfluramine and l-norfenfluramine was comparable to that of the corresponding racemates. Based on the results in DBA/2 mice and other considerations, l-norfenfluramine appears to be a particularly attractive candidate for further evaluation as a novel, enantiomerically pure antiseizure medication