Liquid chromatographic methods for determination of the new antiepileptic drugs stiripentol, retigabine, rufinamide and perampanel: A comprehensive and critical review

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.

Biodegradation of isoproturon by Escherichia coli expressing a Pseudomonas putida catechol 1,2-dioxygenase gene

The phenylurea herbicides are persistent in soil and water, necessitating the creation of methods for removing them from the environment. This study aimed to examine the soil microbial diversity, searching for local bacterial isolates able to efficiently degrade the phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1, 1-dimethylurea (IPU). The best isolates able to effectively degrade IPU were selected, characterized, and identified as Pseudomonas putida and Acinetobacter johnsonii. The catechol 1, 2-dioxygenase enzyme's catA gene was amplified, cloned, and expressed in E. coli M15. The Expressed E. coli showed high degradation efficiency (44.80%) as analyzed by HPLC after 15 days of inoculation in comparison to P. putida (21.60%). The expression of the catA gene in P. putida and expressed E. coli was measured using quantitative polymerase chain reaction (qPCR). The results displayed a significant increase in the mRNA levels of the catA gene by increasing the incubation time with IPU. Hydrophilic interaction chromatography (HILIC) mass spectrometry analysis revealed that three intermediate metabolites, 1-(4-isopropylphenyl)-3-methylurea (MDIPU), 4-Isopropylaniline (4-IA) and 1-(4-isopropylphenyl) urea (DDIPU) were generated by both P. putida and expressed E. coli. In addition, IPU-induced catA activity was detected in both P. putida and expressed E. coli. The supernatant of both P. putida and expressed E. coli had a significant influence on weed growth. The study clearly exhibited that P. putida and expressed E. coli were capable of metabolizing IPU influentially and thus could be utilized for bioremediation and biodegradation technology development.

Nose-to-brain delivery of perampanel formulated in a self-microemulsifying drug delivery system improves anticonvulsant and anxiolytic activity in mice

Perampanel (PER) is a potent third-generation antiepileptic drug only available for oral administration. Additionally, PER has shown potential in managing epilepsy comorbidities such as anxiety. Previously, we demonstrated that the intranasal (IN) administration of PER, loaded in a self-microemulsifying drug delivery system (SMEDDS), improved brain-targeting and exposure in mice. Herein, we investigated PER brain biodistribution, its anticonvulsant and anxiolytic effects, and its potential olfactory and neuromotor toxicity after IN administration to mice (1 mg/kg). PER showed a rostral-caudal brain biodistribution pattern when administered intranasally. At short times post-nasal dosing, high PER concentrations were found in olfactory bulbs (olfactory bulbs/plasma ratios of 1.266 ± 0.183 and 0.181 ± 0.027 after IN and intravenous administrations, respectively), suggesting that a fraction of the drug directly reaches brain through the olfactory pathway. In maximal electroshock seizure test, IN PER protected 60% of mice against seizure development, a substantially higher value than the 20% protected after receiving oral PER. . PER also demonstrated anxiolytic effects in open field and elevated plus maze tests. Buried food-seeking test showed no signs of olfactory toxicity. Neuromotor impairment was found in rotarod and open field tests at the times of PER maximum concentrations after IN and oral administrations. Nevertheless, neuromotor performance was improved after repeated administrations. Compared with IN vehicle, PER IN administration decreased brain levels of L-glutamate (0.91 ± 0.13 mg/mL vs 0.64 ± 0.12 mg/mL) and nitric oxide (100 ± 15.62% vs 56.62 ± 4.95%), without interfering in GABA levels. Altogether, these results suggest that the IN PER delivery through the developed SMEDDS can be a safe and promising alternative to oral treatment, which support the design of clinical studies to evaluate the IN PER delivery to treat epilepsy and neurological-related conditions as anxiety.

Intranasal Microemulsion as an Innovative and Promising Alternative to the Oral Route in Improving Stiripentol Brain Targeting

Stiripentol (STP) is a new-generation antiepileptic only available for oral administration. However, it is extremely unstable in acidic environments and undergoes gastrointestinal slow and incomplete dissolution. Thus, STP intranasal (IN) administration might overcome the high oral doses required to achieve therapeutic concentrations. An IN microemulsion and two variations were herein developed: the first contained a simpler external phase (FS6); the second one 0.25% of chitosan (FS6 + 0.25%CH); and the last 0.25% chitosan plus 1% albumin (FS6 + 0.25%CH + 1%BSA). STP pharmacokinetic profiles in mice were compared after IN (12.5 mg/kg), intravenous (12.5 mg/kg), and oral (100 mg/kg) administrations. All microemulsions homogeneously formed droplets with mean sizes ≤16 nm and pH between 5.5 and 6.2. Compared with oral route, IN FS6 resulted in a 37.4-fold and 110.6-fold increase of STP plasmatic and brain maximum concentrations, respectively. Eight hours after FS6 + 0.25%CH + 1%BSA administration, a second STP brain concentration peak was observed with STP targeting efficiency being 116.9% and direct-transport percentage 14.5%, suggesting that albumin may potentiate a direct STP brain transport. The relative systemic bioavailability was 947% (FS6), 893% (FS6 + 0.25%CH), and 1054% (FS6 + 0.25%CH + 1%BSA). Overall, STP IN administration using the developed microemulsions and significantly lower doses than those orally administrated might be a promising alternative to be clinically tested.

SERS Detection of the Anti-Epileptic Drug Perampanel in Human Saliva

Surface-Enhanced Raman Scattering (SERS) can obtain the spectroscopic response of specific analytes. In controlled conditions, it is a powerful quantitative technique. However, often the sample and its SERS spectrum are complex. Pharmaceutical compounds in human biofluids with strong interfering signals from proteins and other biomolecules are a typical example. Among the techniques for drug dosage, SERS was reported to detect low drug concentrations, with analytical capability comparable to that of the assessed High-Performance Liquid Chromatography. Here, for the first time, we report the use of SERS for Therapeutic Drug Monitoring of the Anti-Epileptic Drug Perampanel (PER) in human saliva. We used inert substrates decorated with gold NPs deposited via Pulsed Laser Deposition as SERS sensors. We show that it is possible to detect PER in saliva via SERS after an optimized treatment of the saliva sample. Using a phase separation process, it is possible to extract all the diluted PER in saliva from the saliva phase to a chloroform phase. This allows us to detect PER in the saliva at initial concentrations of the order of 10^-7 M, thus approaching those of clinical interest.

A brief review on critical analytical aspects for quantification of ambroxol in biological samples

Ambroxol (AMB) is a member of the expectorant class, widely used as a secreolytic agent in patients to break up secretions. AMB is rapidly and effectively distributed from blood to tissue. The lungs have the highest concentration of AMB; accumulation of AMB in human lung tissue was detected at concentrations 15- to 20-fold greater than those reported in the circulation. Because of its wide range of actions and therapeutic applications may be worth looking into, particularly for respiratory symptoms, antioxidant, anti-inflammatory, influenza, and rhinovirus infections. Though several analytical methodologies have been established and confirmed for the AMB analysis in matrices of pharmaceutical and biological origins, novel sustainable, and economical methods are still to be choice of protocol to increase its sensitivity, reliability, and repeatability. Therefore, the present review offers an overview of critical analytical aspects regarding the HPLC, LC-MS/MS, HPTLC, capillary electrophoresis, spectrophotometry, and electrochemical methods for quantifying AMB in pharmaceutical and biological samples. Furthermore, this review will thoroughly discuss the physicochemical properties, stability, extraction conditions, instrumentation, and operational parameters of the targeted analyte. As a result, for the first time, this review complies with vital background information and an up-to-date interpretation of research undertaken by anticipated methodologies examined and implemented for the pharmaceutical analysis AMB.

Intranasal delivery of lipid-based nanosystems as a promising approach for brain targeting of the new-generation antiepileptic drug perampanel

Perampanel (PER), a new-generation antiepileptic drug effective against different types of seizures, has already demonstrated a potential in status epilepticus therapy. Considering the growing interest of intranasal (IN) administration for nose-to-brain delivery, PER could be envisioned as a good candidate for this route, especially if formulated in a lipid-based nanosystem. With that purpose, a hydrophobic formulation (FO1.2) and a self-microemulsifying drug delivery system (SMEDDS) (FH5) loaded with PER were developed and characterized. Following PER IN administration (1 mg/kg) to mice, its pharmacokinetics was characterized and compared with intravenous and oral routes. Histopathological toxicity was also examined after a 7-day repeated dose study. FH5 homogeneously formed nanodroplets upon dispersion (20.07 ± 0.03 nm), showing a sustained in vitro PER release profile up to 4 h. By IN route, PER brain delivery was more extensive with FH5 (C_max and AUC of 52.32 ng/g and 190.35 ng.h/g for FO1.2; 93.87 ng/g and 257.75 ng.h/g for FH5). Maximum brain concentration and total brain exposure were higher than those obtained after oral dosage, with maximum PER concentrations reached significantly faster than post-oral administration (15 min vs 2 h). An improvement in PER plasmatic concentration was also obtained, demonstrated by high relative bioavailability values (134.1% for FH5 and 107.8% for FO1.2). PER absolute plasma bioavailability after IN delivery was 55.5% for FH5 and 44.6% for FO1.2, ensuring a somewhat improved targeting of PER to the brain by the IN route compared to the IV route. No signs of toxicity were found by histopathologic evaluation. Results suggest that IN administration of PER might be a feasible and safe approach for acute and chronic epilepsy management, especially using delivery systems as SMEDDS.

Study of the metabolic stability profiles of perampanel, rufinamide and stiripentol and prediction of drug interactions using HepaRG cells as an in vitro human model

New-generation antiepileptic drugs as perampanel, rufinamide and stiripentol emerged as alternatives in chronic epilepsy polytherapy. Hence, their metabolic stability and potential involvement in relevant drug-drug interactions (DDI) are of great clinical interest, being HepaRG cells herein used as an in vitro human model. To characterize their metabolic stability profiles, HepaRG cells were incubated with perampanel (1 μM), rufinamide (100 μM) or stiripentol (5 μM) for 12-h. HepaRG cells, pretreated with known CYP450 isoenzymes inducers (rifampicin, phenytoin, phenobarbital, omeprazole and carbamazepine), were also incubated with perampanel, rufinamide or stiripentol to assess possible DDI mediated by CYP induction. Results suggest a considerable decrease in perampanel and stiripentol concentrations over 12-h; contrary, rufinamide concentrations did not variated. Cells pretreatment with all inducers significantly decreased stiripentol concentrations (between 20.3% and 31.9%), suggesting a considerable potential for DDI. Rufinamide concentrations only decreased when preincubated with rifampicin and with the highest tested concentrations of the remaining inducers. Perampanel levels decreased with rifampicin, carbamazepine and phenobarbital, supporting the involvement of CYP3A4-mediated metabolism. Besides relevant information concerning the metabolic stability profile and potential DDIs of the new antiepileptics here studied, it was also reinforced the HepaRG cells suitability as a reliable in vitro model to foresee in vivo metabolism in humans.

Current development of bioanalytical sample preparation techniques in pharmaceuticals

Sample preparation is considered as the bottleneck step in bioanalysis because each biological matrix has its own unique challenges and complexity. Competent sample preparation to extract the desired analytes and remove redundant components is a crucial step in each bioanalytical approach. The matrix effect is a key hurdle in bioanalytical sample preparation, which has gained extensive consideration. Novel sample preparation techniques have advantages over classical techniques in terms of accuracy, automation, ease of sample preparation, storage, and shipment and have become increasingly popular over the past decade. Our objective is to provide a broad outline of current developments in various bioanalytical sample preparation techniques in chromatographic and spectroscopic examinations. In addition, how these techniques have gained considerable attention over the past decade in bioanalytical research is mentioned with preferred examples. Modern trends in bioanalytical sample preparation techniques, including sorbent-based microextraction techniques, are primarily emphasized.

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Bioanalytical sampling techniques are described with suitable applications in pharmaceuticals.

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The pros and cons of each bioanalytical sampling techniques are described.

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Relevant biological matrices are outlined.

Trace level determination of eleven nervous system-active pharmaceutical ingredients by switchable solvent-based liquid-phase microextraction and gas chromatography-mass spectrometry with matrix matching calibration strategy

This study utilized switchable solvent liquid-phase microextraction (SS-LPME) to enrich eleven nervous system active pharmaceutical ingredients (APIs) from aqueous samples for their determination at trace levels by gas chromatography mass spectrometry. The analytes selected for the study included APIs utilized in antidepressant, antipsychotic, antiepileptic, and anti-dementia drugs. Parameters of the microextraction method including switchable solvent volume, concentration and volume of the trigger agent (sodium hydroxide), and sample agitation period were optimized univariately to boost extraction efficiency. Under the optimum conditions, the detection limits calculated for the analytes were in the range of 0.20-8.0 ng/mL, and repeatability for six replicate measurements as indicated by percent relative standard deviation values were below 10%. Matrix matching calibration strategy was used to enhance quantification accuracy for the analytes. The percent recovery results calculated for the eleven analytes ranged between 86 and 117%.

pH-induced homogeneous liquid-liquid microextraction method based on new switchable deep eutectic solvent for the extraction of three antiepileptic drugs from breast milk

Aim: A pH-induced homogeneous liquid-liquid microextraction (HLLME) using a new switchable deep eutectic solvent has been used for the extraction of three antiepileptic drugs from breast milk samples. Methodology: This method is based on phase separation by changing pH. An ammonia solution and a phosphocholine chloride: hexanoic acid: p-aminophenol deep eutectic solvents were used as the phase separation agent and extraction solvent, respectively. Results: Significant factors were studied and the detection limits and enrichment factors were in the ranges of 0.009-0.19 ng ml^-1 and 182-212 for the analytes, respectively. Also, linear ranges were wide (0.63-500 ng ml^-1) and the method precision was acceptable. Conclusion: The introduced method was successfully applied for the determination of the analyte concentrations in breast milk samples.