Usefulness of saliva for perampanel therapeutic drug monitoring

Clinical research for saliva-based therapeutic drug monitoring of linezolid

AIMS

Linezolid is primarily used to treat of methicillin-resistant Staphylococcus aureus and multidrug-resistant tuberculosis infections. Thrombocytopenia due to linezolid usage is a concern, and therapeutic drug monitoring has been reported to be effective in its prevention. Plasma concentrations provide valuable information for treatment decisions; however, collecting plasma samples can be burdensome for both patients and healthcare providers. Therefore, there is interest in saliva as an alternative for monitoring, considering its potential to replace plasma samples.

METHODS

Patients hospitalized at Hokkaido University Hospital and Hokkaido Spinal Cord Injury Center between April 2022 and July 2024, who received oral or intravenous linezolid treatment, were enrolled. The concentrations of linezolid were simultaneously measured in plasma and saliva samples. We determined the concentration profiles of linezolid in the saliva and examined the correlation between saliva and plasma linezolid concentrations.

RESULTS

Eighteen patients receiving linezolid were enrolled. The average of saliva/plasma (S/P) concentration ratios of linezolid were 1.018. A strong correlation was found between the salivary and plasma concentrations of linezolid (R = .833, P < .001). Notably, in patients receiving intravenous administration of linezolid, the correlation was even more pronounced (R = .885, P < .001). Additionally, when focusing on the S/P ratio of the trough concentrations in the morning and at night, the S/P ratios at night were much closer to 1.0.

CONCLUSION

The concentrations of linezolid in plasma and saliva were similar, indicating their potential applicability in clinical settings. The monitoring of linezolid concentrations in saliva has been shown to be particularly suitable for patients receiving intravenous administration.

Determination of Antiepileptics in Biological Samples-A Review

Epilepsy remains a disease that affects many people around the world. With the development of new drugs to treat this condition, the importance of therapeutic drug monitoring continues to rise and remains a challenge for the medical community. This review article explores recent advances in the detection of antiepileptic drugs across various sample types commonly used for drug monitoring, with a focus on their applications and impact. Some of these new methods have proven to be simpler, greener, and faster, making them easier to apply in the context of therapeutic drug monitoring. Additionally, besides the classic use of blood and its derivatives, there has been significant research into the application of alternative matrices due to their ease of sample collection and capacity to reflect drug behavior in blood. These advances have contributed to increasing the efficacy of therapeutic drug monitoring while enhancing its accessibility to the population.

Monitoring levetiracetam concentration in saliva during pregnancy is stable and feasible

AIMS

This multicenter prospective cohort study (registration no. ChiCTR2000032089) aimed to investigate the relationship between saliva and plasma levetiracetam concentrations to determine whether saliva could be used for routine monitoring of levetiracetam during pregnancy.

METHODS

The slot concentrations of levetiracetam in simultaneously obtained saliva and plasma samples were measured using UPLC-MS/MS. The correlations between saliva and plasma levetiracetam concentrations and the dose-normalized concentrations were compared among pregnant women in different stages and nonpregnant control participants with epilepsy.

RESULTS

In total, 231 patients with 407 plasma and saliva sample pairs were enrolled from 39 centers. Linear relationships between salivary and plasma levetiracetam concentrations were reported in the enrolled population (r = 0.898, p < 0.001), including pregnant (r = 0.935, p < 0.001) and nonpregnant participants (r = 0.882, p < 0.001). Plasma concentrations were moderately higher than saliva concentrations, with ratios of saliva to plasma concentrations of 0.98 for nonpregnant women, 0.98, 1, and 1.12 for pregnant women during the first trimester, the second trimester, the and third trimester, respectively. The effective range of saliva levetiracetam concentration was found to be 9.98 μg/mL (lower limit) with an area under the curve (AUC) of 0.937 (95% confidence intervals, 0.915-0.959), sensitivity of 88.9%, specificity of 86.8%, and p < 0.001, to 24.05 μg/mL (upper limit) with an AUC of 0.952 (0.914-0.99), sensitivity of 100%, specificity of 92.3%, and p = 0.007.

CONCLUSION

The saliva/plasma concentration ratio of levetiracetam remains constant during pregnancy and is similar to that in non-pregnant individuals. Monitoring levetiracetam concentration in saliva during pregnancy should be widely promoted.

Research Status, Synthesis and Clinical Application of Antiepileptic Drugs

According to the 2017 ILAE's official definition, epilepsy is a slow brain disease state characterized by recurrent episodes. Due to information released by ILAE in 2017, it can be divided into four types, including focal epilepsy, generalized epilepsy, combined generalized, and focal epilepsy, and unknown epilepsy. Since 1989, 24 new antiepileptic drugs have been approved to treat different types of epilepsy. Besides, there are a variety of antiepileptic medications under clinical monitoring. These novel antiepileptic drugs have plenty of advantages. Over the past 33 years, there have been many antiepileptic drugs on the mearket, but no one has been found that can completely cure epilepsy. In this paper, the mentioned drugs were classified according to their targets, and the essential information, and clinical studies of each drug were described. The structure-activity relationship of different chemical structures was summarized. This paper provides help for the follow-up research on epilepsy drugs.

Therapeutic Drug Monitoring of Perampanel in Children With Refractory Epilepsy: Focus on Influencing Factors on the Free-Perampanel Concentration

BACKGROUND

This study aimed to assess the effect of perampanel dose, age, sex, and antiseizure medication cotherapy on steady-state free-perampanel concentration in children with refractory epilepsy, as well as the relationship between inflammation and the pharmacokinetics of perampanel.

METHODS

This prospective study in China included 87 children with refractory epilepsy treated with adjunctive perampanel therapy. Free and total perampanel concentrations in plasma were determined using liquid chromatography-tandem mass spectrometry. Free-perampanel concentration was compared among patients with various potential influencing factors.

RESULTS

A total of 87 pediatric patients (44 female children) aged 2-14 years were enrolled. The mean free-perampanel concentration and free concentration-to-dose (CD) ratio in plasma were 5.7 ± 2.7 ng/mL (16.3 ± 7.7 nmol/L) and 45.3 ± 21.0 (ng/mL)/(mg/kg) [129.6 ± 60.1 (nmol/L)/(mg/kg)], respectively. The protein binding of perampanel in plasma was 97.98%. A linear relationship was observed between perampanel dose and free concentration in plasma, and a positive relationship was found between the total and free-perampanel concentrations. Concomitant use of oxcarbazepine reduced the free CD ratio by 37%. Concomitant use of valproic acid increased the free CD ratio by 52%. Five patients had a plasma high-sensitivity C-reactive protein (Hs-CRP) level of >5.0 mg/L (Hs-CRP positive). The total and free CD ratios of perampanel were increased in patients with inflammation. Two patients with inflammation developed adverse events, which disappeared as the Hs-CRP level returned to normal, and neither required perampanel dose reduction. Age and sex did not influence the free-perampanel concentration.

CONCLUSIONS

This study found complex drug interactions between perampanel and other concomitant antiseizure medications, providing valuable information to enable clinicians to apply perampanel in the future reasonably. In addition, it may be important to quantify both the total and free concentrations of perampanel to assess complex pharmacokinetic interactions.

Therapeutic Salivary Monitoring of Perampanel in Patients with Epilepsy Using a Volumetric Absorptive Microsampling Technique

The objective of this study was to validate a novel assay using the volumetric absorptive microsampling (VAMS) technique combined with liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for the determination of the antiseizure medication perampanel in saliva and its clinical applicability in patients with epilepsy. VAMS tips were loaded with 30 μL of saliva and dried for 60 min. Analytes were extracted with methanol. The supernatant was evaporated under a gentle stream of nitrogen and reconstituted with 60 μL of methanol. Separation and quantification were achieved on a monolithic column connected to a mass spectrometer. Calibration curves were linear between 0.5 and 300 ng/mL. Intra- and inter-day accuracy was within 85.6-103.2% and intra-day and inter-day precision did not exceed 12.1%. Perampanel was stable in samples collected by VAMS and stored under different storage conditions. The VAMS-LC-MS/MS method was validated according to internationally accepted criteria and tested in patients with epilepsy who were receiving a combination of perampanel and other antiseizure medications. The method showed adequate bioanalytical performances, holding great potential as an alternative strategy to support domiciliary TDM in patients with epilepsy treated with perampanel according to the simplicity of sample collection.

Monitoring Salivary Concentrations of Tedizolid and Linezolid Using Rats

BACKGROUND AND OBJECTIVE

Therapeutic drug monitoring (TDM) is an effective tool for the management of patients who are administered linezolid. The use of saliva for TDM has potential advantages over the use of plasma; however, only a few reports have compared drug concentrations in the saliva and plasma. Moreover, there are no reports on the salivary concentration of tedizolid, an oxazolidinone antibiotic similar to linezolid. In the present study, the concentrations of tedizolid and linezolid in rat submandibular saliva were compared with those measured in the plasma.

METHODS

Tedizolid (10 mg/kg, n = 6) and linezolid (12 mg/kg, n = 5) were administered via the rat tail vein. Submandibular saliva and plasma samples were collected for up to 8 h after the initiation of drug administration, and assayed for the concentrations of tedizolid and linezolid.

RESULTS

A strong correlation was found between the saliva and plasma concentrations of tedizolid (r = 0.964, p < 0.001) and linezolid (r = 0.936, p < 0.001). The value of tedizolid maximum concentration of drug (C_max) was 0.99 ± 0.08 µg/mL in the saliva and 14.46 ± 1.71 µg/mL in the plasma. Meanwhile, the C_max of linezolid was 8.01 ± 1.42 µg/mL in the saliva and 13.00 ± 1.90 µg/mL in the plasma. According to these results, the saliva/plasma concentration ratios of tedizolid and linezolid in rats were 0.0513 ± 0.0080 and 0.6341 ± 0.0339, respectively.

CONCLUSIONS

Considering the correlation between saliva and plasma concentrations of tedizolid and linezolid, as well as the characteristics of saliva, the results of this study suggest that saliva is a useful matrix for TDM.

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.

Saliva as Blood Alternative in Therapeutic Monitoring of Teriflunomide-Development and Validation of the Novel Analytical Method

Therapeutic drug monitoring (TDM) is extremely helpful in individualizing dosage regimen of drugs with narrow therapeutic ranges. It may also be beneficial in the case of drugs characterized by serious side effects and marked interpatient pharmacokinetic variability observed with leflunomide and its biologically active metabolite, teriflunomide. One of the most popular matrices used for TDM is blood. A more readily accessible body fluid is saliva, which can be collected in a much safer way comparing to blood. This makes it especially advantageous alternative to blood during life-threatening SARS-CoV-2 pandemic. However, drug’s saliva concentration is not always a good representation of its blood concentration. The aim of this study was to verify whether saliva can be used in TDM of teriflunomide. We also developed and validated the first reliable and robust LC-MS/MS method for quantification of teriflunomide in saliva. Additionally, the effect of salivary flow and swab absorptive material from the collector device on teriflunomide concentration in saliva was evaluated. Good linear correlation was obtained between the concentration of teriflunomide in plasma and resting saliva (p < 0.000016, r = 0.88), and even better between plasma and the stimulated saliva concentrations (p < 0.000001, r = 0.95) confirming the effectiveness of this non-invasive method of teriflunomide’s TDM. The analyzed validation criteria were fulfilled. No significant influence of salivary flow (p = 0.198) or type of swab in the Salivette device on saliva’s teriflunomide concentration was detected. However, to reduce variability the use of stimulated saliva and synthetic swabs is advised.

Sensing the Anti-Epileptic Drug Perampanel with Paper-Based Spinning SERS Substrates

The applications of SERS in therapeutic drug monitoring, or other fields of analytical chemistry, require the availability of sensitive sensors and experimental approaches that can be implemented in affordable ways. In this contribution, we show the production of cost-effective SERS sensors obtained by depositing Lee-Meisel Ag colloids on filter paper either by natural sedimentation or centrifugation. We have characterized the morphological and plasmonic features of the sensors by optical microscopy, SEM, and UV-Vis spectroscopy. Such sensors can be used to quantify by SERS the anti-epileptic drug Perampanel (in the concentration range 1 × 10⁻⁴–5 × 10⁻⁶ M) by spinning them during the micro-Raman measurements on the top of a custom device obtained from spare part hard disk drives. This approach minimizes laser-induced heating effects and allows averaging over the spatial non-uniformity of the sensor.

The Effect of Plasma Protein Binding on the Therapeutic Monitoring of Antiseizure Medications

Epilepsy is a widely diffused neurological disorder including a heterogeneous range of syndromes with different aetiology, severity and prognosis. Pharmacological treatments are based on the use, either in mono- or in polytherapy, of antiseizure medications (ASMs), which act at different synaptic levels, generally modifying the excitatory and/or inhibitory response through different action mechanisms. To reduce the risk of adverse effects and drug interactions, ASMs levels should be closely evaluated in biological fluids performing an appropriate Therapeutic Drug Monitoring (TDM). However, many decisions in TDM are based on the determination of the total drug concentration although measurement of the free fraction, which is not bound to plasma proteins, is becoming of ever-increasing importance since it correlates better with pharmacological and toxicological effects. Aim of this work has been to review methodological aspects concerning the evaluation of the free plasmatic fraction of some ASMs, focusing on the effect and the clinical significance that drug-protein binding has in the case of widely used drugs such as valproic acid, phenytoin, perampanel and carbamazepine. Although several validated methodologies are currently available which are effective in separating and quantifying the different forms of a drug, prospective validation studies are undoubtedly needed to better correlate, in real-world clinical contexts, pharmacokinetic monitoring to clinical outcomes.

Feasibility of Using Oral Fluid for Therapeutic Drug Monitoring of Antiepileptic Drugs

Therapeutic drug monitoring (TDM) of antiepileptic drugs (AED) using blood is well established but limited by its invasiveness, accessibility, cost, interpretation errors, and related disturbances in protein binding. TDM using oral fluid (OF) could overcome these limitations. This paper provides a summary of the current evidence for using OF as a matrix to perform TDM of AEDs, as well as practical considerations. A literature search of MEDLINE, EMBASE, and the Cochrane Library was conducted on April 9, 2018 (and then updated on May 20, 2020) using all AEDs as keywords along with "oral fluid," "saliva," "salivary," "seizure," "epilepsy," "antiepileptic," and "anticonvulsant." A total of 18 relevant articles were found and included in this review. There is evidence to suggest that AED TDM using OF is feasible and that reference ranges can be calculated for the following drugs: carbamazepine, ethosuximide, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, phenobarbital, phenytoin, primidone, topiramate, and valproic acid. For all other AEDs, there is either a lack of evidence on the feasibility of TDM using OF or the evidence indicates that TDM using OF is not feasible. Practical considerations should include the timing and method of OF collection (stimulated or unstimulated) due to their probable impact on the reliability of AED TDM. Using OF may improve the acceptability and accessibility and reduce the cost of AED TDM. Clinical implementation requires standardized collection protocols, more rigorously defined OF reference ranges, and further studies to determine the relevance to clinically important outcomes.