Simple HPLC-UV Method for Therapeutic Drug Monitoring of 12 Antiepileptic Drugs and Their Main Metabolites in Human Plasma

The objective of the present report was to develop and validate a simple, selective, and reproducible high-performance liquid chromatography method with UV detection suitable for routine therapeutic drug monitoring of the most commonly used antiepileptic drugs and some of their metabolites. Simple precipitation of plasma proteins with acetonitrile was used for sample preparation. 10,11-dihydrocarbamazepine was used as an internal standard. Chromatographic separation of the analytes was achieved by gradient elution on a Phenyl-Hexyl column at 40 °C, using methanol and potassium phosphate buffer (25 mM; pH 5.1) as a mobile phase. The method was validated according to the FDA guidelines for bioanalytical method validation. It showed to be selective, accurate, precise, and linear over the concentration ranges of 1-50 mg/L for phenobarbital, phenytoin, levetiracetam, rufinamide, zonisamide, and lacosamide; 0.5-50 mg/L for lamotrigine, primidone, carbamazepine and 10-monohydroxycarbazepine; 0.2-10 mg/L for carbamazepine metabolites: 10,11-trans-dihydroxy-10,11-dihydrocarbamazepine and carbamazepine-10,11-epoxide; 0.1-10 mg/L for oxcarbazepine; 2-100 mg/L for felbamate and 3-150 mg/L for ethosuximide. The suitability of the validated method for routine therapeutic drug monitoring was confirmed by quantification of the analytes in plasma samples from patients with epilepsy on combination antiepileptic therapy.

Carbamazepine and carbamazepine-epoxide concentrations in mothers, colostrum, and breastfed newborns: Comparison with concentrations determined during delivery and in the mature milk period

OBJECTIVE

To obtain information on the transport of carbamazepine and its active metabolite carbamazepine-epoxide from mother to colostrum and breastfed newborns.

METHODS

In this cohort study, carbamazepine and carbamazepine-epoxide concentrations in maternal serum (162 women), milk (i.e., colostrum) and breastfed newborn serum were analysed between the 1st and 5th days after delivery from November 1990 to February 2021. The measured concentrations were compared with the delivery and mature milk periods. The effect of the combination with both enzyme-inducing antiseizure medication and valproic acid was also evaluated.

RESULTS

Carbamazepine concentrations varied from 1.0 to 11.2 mg/L (epoxide 0.3-4.4 mg/L) in maternal serum, from 0.5 to 6.8 mg/L (epoxide 0.3-2.4 mg/L) in milk and from 0.5 to 4.7 mg/L (epoxide 0.3-1.7 mg/L) in newborn serum. The median milk/maternal serum concentration ratio of carbamazepine was 0.45 (epoxide 0.71), the median newborn/maternal serum concentration ratio of carbamazepine was 0.20 (epoxide 0.41), and the median newborn serum/milk concentration ratio of carbamazepine was 0.38 (epoxide 0.50). A highly significant correlation was found between the milk and maternal serum concentrations of both carbamazepine and carbamazepine-epoxide and between the milk and newborn serum concentrations of carbamazepine.

CONCLUSIONS

In the serum of breastfed newborns, only one concentration of carbamazepine reached the reference range used for the general epileptic population, and more than half was below the lower limit of quantification. Routine monitoring of serum carbamazepine concentrations is not required in breastfed newborns. However, observation of newborns is desirable, and if signs of potential adverse reactions are noted, the serum concentrations in newborns should be measured.

Monitoring of lamotrigine concentrations in mothers, colostrum, and breastfed newborns during the early postpartum period

OBJECTIVE

To analyse the concentrations of lamotrigine in maternal serum, colostrum, and serum of breastfed newborns, and to evaluate the effect of comedication with enzyme-inducing antiseizure medication and valproic acid.

METHODS

This cohort study collected data from 158 women and 143 breastfed newborns. Maternal serum, milk (i.e., colostrum), and newborn serum samples were collected between the 2nd and 5th postnatal days, and lamotrigine concentrations were measured by high-performance liquid chromatography.

RESULTS

The median lamotrigine concentrations were 2.7 mg/L in maternal serum, 1.4 mg/L in milk, and 1.7 mg/L in newborn serum. The median milk/maternal serum concentration ratio was 0.60, the median newborn/maternal serum concentration ratio was also 0.60, and the median newborn serum/milk concentration ratio was 1.00. A significant correlation was observed between milk and maternal serum concentrations and between newborn serum and milk concentrations, maternal serum concentrations, maternal daily dose, and dose related to maternal body weight.

CONCLUSIONS

Exposure to lamotrigine in breastfed newborns is lower than exposure during pregnancy. However, by the same dose by the same mother, lamotrigine concentrations in both maternal serum and milk increase significantly after delivery. This finding, together with the immature function of eliminating enzymes in newborns, may be the reason for reaching concentrations in the reference range used for the general epileptic population in breastfed newborns. Therapeutic monitoring of breastfed newborns serum concentrations of lamotrigine is not mandatory; however, if signs of possible adverse events are noted, newborn serum concentrations should be analysed.

Development and evaluation of a simple and easy HPLC-UV system simultaneously suitable for determination of 24 anti-epileptic drugs in plasma

This paper aims to establish a simple and easy HPLC system coupled with UV detector suitable for simultaneous determination of 24 antiepileptic drugs in human plasma. Optimized chromatographic separation was performed on a ZORBAX Eclipse Plus-C18 (4.6 mm×150 mm, 3.5 μm) column with acetonitrile and 5 mM potassium dihydrogen phosphate water solution as mobile phase. 24 antiepileptic drugs were divided into three groups and eluted with different gradient procedures, respectively. The column temperature was maintained at 35 °C and the detection wavelength was set at 210 nm. Plasma was processed with ethyl acetate or acetonitrile. The calibration curves of 24 antiepileptic drugs demonstrated good linearity within the test range (r > 0.996). The intra- and inter-batch precision and accuracy were all less than 15%, while extraction recoveries were in the range of 74.57%∼90.89% with the RSD values less than 15%. The validated methods have been successfully applied to determination of some antiepileptic drugs in rat or patient plasma. Those results indicated that the developed methods were simple and easy, and could be suitable for the determination of 24 antiepileptic drugs in plasma just by changing the gradient elution procedures of mobile phase. This article is protected by copyright. All rights reserved.

Detection of carbamazepine in saliva based on surface-enhanced Raman spectroscopy

Carbamazepine (CBZ) is a commonly used drug for the treatment of epilepsy. Due to the narrow effective range, CBZ concentration was usually monitored with blood draw from patients. Frequent blood draw is inconvenient and causes physical and psychological pain. Therefore, highly-sensitive, rapid, label-free, and non-invasive drug detection methods can be alternatives to bring a relief. In this work, we have proposed a method for the non-invasive detection of CBZ using surface-enhanced Raman spectroscopy (SERS). Gold-silver core-shell nanomaterial substrates were prepared and optimized. Salivary CBZ concentration was measured with SERS as a non-invasive alternative to blood draw. The results showed that there was a linear relationship between SERS response and CBZ concentration in the entire measured range of 10^-1 ∼ 10^-8 mol/L. The detection limit of this method was 1.26 × 10^-9 mol/L. Satisfactory repeatability and stability were also demonstrated. Due to its high sensitivity and ease of operation, the proposed method can serve as an alternative to blood draw for non-invasively monitoring CBZ concentration. It also has great potentials in many other applications of biomedical sciences.

Therapeutic monitoring of carbamazepine and its active metabolite during the 1st postnatal month: Influence of drug interactions

OBJECTIVE

To receive information about carbamazepine and its active metabolite 10,11-epoxide transport into mature milk and suckling infants.

METHODS

In this cohort study, maternal serum, mature milk, and infant serum carbamazepine and epoxide levels were measured between the 6th and 29th postnatal day (carbamazepine in 1990-2017, epoxide in 1997-2017). Paired maternal serum, infant serum and milk levels were used for the assessment of ratios of this levels. The influence of combined treatment with enzyme-inducing antiepileptic drugs and valproic acid was assessed. Relationship between maternal serum, infant serum, and milk levels was also evaluated.

RESULTS

Maternal carbamazepine levels were 1.4-10.4 mg/L, milk 0.5-6.7 mg/L and infant 0.5-2.6 mg/L. Maternal 10,11-epoxide levels were 0.3-5.4 mg/L, milk 0.3-3.7 mg/L and infant 0.3-0.6 mg/L. Highly significant correlations were observed exclusively between milk and maternal serum levels of both carbamazepine and 10,11-epoxide. Concomitant administration of enzyme-inducing antiepileptic drugs significantly increased the maternal apparent oral clearance of carbamazepine by approximately 130%. Carbamazepine combined with valproic acid significantly increased epoxide levels in milk and maternal serum but not in breastfed infants.

CONCLUSIONS

In breastfed infants, carbamazepine levels did not reach the lower limit of the therapeutic range used for the general epileptic population, and the majority of epoxide levels were less than the lower limit of quantification. Routine monitoring of carbamazepine in these infants is not compulsory. However, observation of breastfed infants is desirable. If signs of potential adverse reactions are evident, infant serum concentrations should be monitor.

Simultaneous Determination of Drugs Affecting Central Nervous System (CNS) in Bulk and Pharmaceutical Formulations Using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS)

The quality of medications is important to maintain the overall health care of patients. This study aims to develop and validate a spectrophotometric method using multivariate curve resolution-alternating least squares (MCR-ALS) with correlation constraint for simultaneous resolution and quantification of selected drugs affecting the central nervous system (imipramine, carbamazepine, chlorpromazine, haloperidol, and phenytoin) in different pharmaceutical dosage forms. Figures of merit such as root-mean-square error of prediction, bias, standard error of prediction, and relative error of prediction for the developed method were calculated. High values of correlation coefficients ranged between 0.9993 and 0.9998 reflected high predictive ability of the developed method. The results are linear in the concentration range of 0.3-5 μg/mL for carbamazepine, 0.3-15 μg/mL for chlorpromazine, 0.5-10 μg/mL for haloperidol, 0.5-10 μg/mL for imipramine, and 3-20 μg/mL for phenytoin. The optimized method was successfully applied for the analysis of the studied drugs in their pharmaceutical products without any separation step. The optimized method was also compared with a reported HPLC method using Student's t test and F ratio at 95% confidence level, and the results showed no significant difference regarding accuracy and precision. The proposed chemometric method is fast, reliable, and cost-effective and can be used as an eco-friendly alternative to chromatographic techniques for the analysis of the studied drugs in commercial pharmaceutical products.

A Short Communication: Lamotrigine Levels in Milk, Mothers, and Breastfed Infants During the First Postnatal Month

BACKGROUND

Lamotrigine has become the most frequently prescribed drug in the treatment of pregnant women with epilepsy. Although some relevant studies have found a wide milk/maternal serum as well as infant/maternal serum concentration ratio, different infant ages at the time of sampling and small number of patients preclude comparison. The aim of this study was to provide a consistent evaluation.

METHODS

Data of 43 nursing women treated by lamotrigine were evaluated retrospectively. The authors followed the transport of lamotrigine during the first postnatal month from mothers to breastfed infants through maternal milk between the years 2002 and 2017.

RESULTS

Lamotrigine concentrations varied from 1.1 to 14.9 mg/L in the maternal serum, from <0.66 to 9.1 mg/L in the milk and between <0.66 and 6.9 mg/L in the infant serum. The milk/maternal serum concentration ratio ranged from <0.18 to 0.74 and the infant/maternal serum concentration ratio measured between <0.15 and 0.74. Highly significant correlations were found between milk and maternal serum levels and between infant serum levels and milk, maternal serum levels, lamotrigine daily dose, and also maternal dose related to the body weight.

CONCLUSIONS

The authors confirmed the wide range of the milk/maternal serum concentration ratio and the infant/maternal serum concentration ratio. Although the degree of lamotrigine exposure to the breastfed infants was smaller than during gestation, 16% of the infant serum levels measured were within the therapeutic range used for the general epileptic population. Lamotrigine concentration monitoring in breastfed infant, in our opinion, is the most relevant aspect for the analysis of actual lamotrigine exposure in infants, especially in those with clinical symptoms.

Primidone inhibits TRPM3 and attenuates thermal nociception in vivo

Supplemental Digital Content is Available in the Text.

The approved antiepileptic drug primidone potently inhibits TRPM3 channels and thereby exerts analgesic properties to chemical pain and thermal hyperalgesia in mice.

The melastatin-related transient receptor potential (TRP) channel TRPM3 is a nonselective cation channel expressed in nociceptive neurons and activated by heat. Because TRPM3-deficient mice show inflammatory thermal hyperalgesia, pharmacological inhibition of TRPM3 may exert antinociceptive properties. Fluorometric Ca²⁺ influx assays and a compound library containing approved or clinically tested drugs were used to identify TRPM3 inhibitors. Biophysical properties of channel inhibition were assessed using electrophysiological methods. The nonsteroidal anti-inflammatory drug diclofenac, the tetracyclic antidepressant maprotiline, and the anticonvulsant primidone were identified as highly efficient TRPM3 blockers with half-maximal inhibition at 0.6 to 6 μM and marked specificity for TRPM3. Most prominently, primidone was biologically active to suppress TRPM3 activation by pregnenolone sulfate (PregS) and heat at concentrations markedly lower than plasma concentrations commonly used in antiepileptic therapy. Primidone blocked PregS-induced Ca²⁺_i influx through TRPM3 by allosteric modulation and reversibly inhibited atypical inwardly rectifying TRPM3 currents induced by coapplication of PregS and clotrimazole. In vivo, analgesic effects of low doses of primidone were demonstrated in mice, applying PregS- and heat-induced pain models, including inflammatory hyperalgesia. Thus, applying the approved drug at concentrations that are lower than those needed to induce anticonvulsive effects offers a shortcut for studying physiological and pathophysiological roles of TRPM3 in vivo.

Quantitative bioanalytical and analytical method development of dibenzazepine derivative, carbamazepine: A review

Bioanalytical methods are widely used for quantitative estimation of drugs and their metabolites in physiological matrices. These methods could be applied to studies in areas of human clinical pharmacology and toxicology. The major bioanalytical services are method development, method validation and sample analysis (method application). Various methods such as GC, LC-MS/MS, HPLC, HPTLC, micellar electrokinetic chromatography, and UFLC have been used in laboratories for the qualitative and quantitative analysis of carbamazepine in biological samples throughout all phases of clinical research and quality control. The article incorporates various reported methods developed to help analysts in choosing crucial parameters for new method development of carbamazepine and its derivatives and also enumerates metabolites, and impurities reported so far.

Dispersive liquid–liquid microextraction for preconcentration and determination of phenytoin in real samples using response surface methodology-high performance liquid chromatography

In the present study, dispersive liquid–liquid microextraction (DLLME) was developed for preconcentration and determination of phenytoin in real samples by high performance liquid chromatography (HPLC).

Modern methods for analysis of antiepileptic drugs in the biological fluids for pharmacokinetics, bioequivalence and therapeutic drug monitoring

Epilepsy is a chronic disease occurring in approximately 1.0% of the world's population. About 30% of the epileptic patients treated with availably antiepileptic drugs (AEDs) continue to have seizures and are considered therapy-resistant or refractory patients. The ultimate goal for the use of AEDs is complete cessation of seizures without side effects. Because of a narrow therapeutic index of AEDs, a complete understanding of its clinical pharmacokinetics is essential for understanding of the pharmacodynamics of these drugs. These drug concentrations in biological fluids serve as surrogate markers and can be used to guide or target drug dosing. Because early studies demonstrated clinical and/or electroencephalographic correlations with serum concentrations of several AEDs, It has been almost 50 years since clinicians started using plasma concentrations of AEDs to optimize pharmacotherapy in patients with epilepsy. Therefore, validated analytical method for concentrations of AEDs in biological fluids is a necessity in order to explore pharmacokinetics, bioequivalence and TDM in various clinical situations. There are hundreds of published articles on the analysis of specific AEDs by a wide variety of analytical methods in biological samples have appears over the past decade. This review intends to provide an updated, concise overview on the modern method development for monitoring AEDs for pharmacokinetic studies, bioequivalence and therapeutic drug monitoring.

Development and validation of an HPLC-UV method for the quantification of carbamazepine in rabbit plasma

An isocratic simple rapid assay has been developed and validated for the determination of carbamazepine (CBZ) in both solution form and rabbit plasma using propylparaben as an internal standard. The assay was performed using a μ-Bondapak C18 (150 mm × 4.6 mm i.d) with a mobile phase consisting of methanol and water (50:50), the flow rate was 1 ml/min and UV detection at 285 nm. The method was found to be specific for CBZ, no interfering peaks were observed with an overall analytical run time of 15 min. Accuracy reported as % recovery were found to be 98.37-100.45% and 97.53-103.58% for inter-day and intra-day accuracies, respectively. Inter-day precision (reproducibility) was found to be 0.53-2.75% RSD, while intra-day precision (repeatability) was found to be 1.06-3.7% RSD for the samples studied. The calibration curve was found to be linear with the equation y = 0.2847x + 0.0138, with a correlation coefficient of 0.9999 (R (2)) over a concentration range of 0.5-40 μg/ml. The limit of quantitation was the lowest concentration. The method is simple and rapid and does not require any preliminary treatment of the sample. The method was fully validated.

Determination of carbamazepine in serum and saliva samples by high performance liquid chromatography with ultraviolet detection

Background/Aim. Carbamazepine is antiepileptic drug widely used for the treatment of epilepsy. Due to low therapeutic index of carbamazepine there is a need for routine measuring its concentrations in biological fluids. The aim of the study was to describe a method for concomitant determination of carbamazepine in the serum and saliva. Methods. Separation of the drug from matrix is achieved by reversedphase chromatography on a C18 column, with a mobile phase of methanol-water-acetic acid (65:34:1) at a flow-rate of 1.0 ml/min. Detection was effected by ultra-violet absorption at 285 nm. The total run time was 5 min. Samples were prepared by alkaline extraction (pH 10) using chlorophorm. Results. Calibration curves were in the range 0.1-5 ?g/mL for serum and saliva samples. Mean recoveries of spiked serum and saliva were 97.59 and 92.30%, respectively. Limits of detection (LOD) of carbamazepine in serum and saliva were 0.166 and 0.178 ?g/mL, respectively. Limits of quantification (LOQ) in the serum and saliva were 0.237 and 0.226 ?g/mL, respectively. The method precision was carried out with coefficient of variation of 2.10% and 4.03% for the serum and saliva, respectively. The obtained data showed that there was a strong correlation between saliva and serum concentrations (r = 0.9481, p < 0.001). Conclusion. The method described here is rapid, precise, accurate and simple, and can be used for quantitative determination of carbamazepine in human serum and saliva after therapy applying. Saliva samples could be used as an alternative matrix for therapeutic drug monitoring of this antiepileptic drug.