Lamotrigine Serum Research Articles

Therapeutic drug monitoring of lamotrigine.

To evaluate the usefulness of routine monitoring of serum lamotrigine concentration. Literature was accessed through MEDLINE (1990-January 2001). Key search terms included lamotrigine, pharmacokinetics, and epilepsy. A decision-making algorithm was used to evaluate the clinical evidence to support or refute the routine use of serum lamotrigine concentrations to adjust doses. The value of serum lamotrigine concentration monitoring remains controversial, primarily because clear relationships between concentration and pharmacologic response (either efficacy or toxicity) have not been demonstrated. Serum concentration monitoring of lamotrigine is not recommended as a tool for routine dose adjustment.

New high-performance liquid chromatographic method for plasma/serum analysis of lamotrigine.

Lamotrigine is an anticonvulsant drug recently approved in Italy for clinical use. Therapeutic monitoring of lamotrigine is relevant for patient management and avoidance of toxicity. The authors describe a simple, sensitive, and highly selective high-performance liquid chromatography method that does not involved extraction for analysis of serum lamotrigine. Serum (20 microL) with internal standard (BW 725 C) was injected directly into a column (25 cm x 4.6 mm) with an internal surface reversed phase (ISRP). The mobile phase consisted of 0.01 mol/L potassium phosphate bibasic (pH 6.0) and acetonitrile (82:18), the flow rate was 1.0 mL/min, and UV detection was optimized at 330 nm. The overall between-run coefficient of variance ranged from 1.89% to 3.25% and the lowest limit of detection was 0.05 mg/L. High linearity (r = 0.9996) in a wide range of concentrations (0.1-20.0 mg/L) and no interference with other antiepileptic drugs, benzodiazepines, and tricyclic antidepressants were the other characteristics of the method. The innovation of this method is the use of ISRP column and the choice of detection wavelength, which allow a shorter analysis time (5-6 minutes). The possibility of direct injection of plasma samples into the column permits a reduction in reagent consumption and in analytic steps, and hence in analytic error.

Simple and rapid HPLC method for simultaneous determination of multiple antiepileptic drugs in human serum

A very rapid, sensitive and reproducible HPLC method was developed for simultaneous determination of eight anti-epileptic drugs (AEDs): lamotrigine, primidone, ethosuximide, sulthiame, felbamate, phenobarbital, carbamazepine, phenytoin and oxcarbazepine-metabolite (10-hydroxy-carbazepine) in human serum. Sample purification requires only protein precipitation with an appropriate reagent. Separation was by reversed-phase HPLC, using a C18 column, 20% acetonitrile and 40 mM phosphoric acid buffer as mobile phase. Column temperature was set at 50°C, and measurement was by UV detection at 205 nm. The inter and intra-assay coefficients of variation (CV) ranged 1.13–7.10% and 1.14–8.49%, respectively. The absolute (measured) and relative (analytic) recoveries of the drugs ranged 96.7%–104.4% and 97.3%–106.1%, respectively. No interference with other common antiepileptic drugs and analgesics were observed. The method requires only 100 μl serum or less. It is very fast (sample preparation and analysis time approx. 23 min for all 9 AEDs), and suitable for routine clinical use, especially for epileptic patients on polytherapy.

Chronic lamotrigine treatment increases rat hippocampal GABA shunt activity and elevates cerebral taurine levels

The mechanism of action of the antiepileptic drug lamotrigine has previously been investigated only in acute experiments and is thought to involve inhibition of voltage-dependent sodium channels. However, lamotrigine is effective against more forms of epilepsies than other antiepileptic drugs that also inhibit sodium channels. We investigated whether chronic lamotrigine treatment may affect cerebral amino acid levels. Rats received lamotrigine, 10 mg/kg/day, for 90 days. The hippocampal level of GABA increased 25%, and the activities of glutamate decarboxylase and succinic semialdehyde/GABA transaminase increased 12 and 21% ( p< 0.05), respectively, indicating increased GABA turnover. The uptake of GABA and glutamate into proteoliposomes remained unaltered. The level of taurine increased 27% in the hippocampus and 16% in the frontal and parietal cortices. The activities of hexokinase and α-ketoglutarate dehydrogenase, remained at control values. Serum lamotrigine was 41.7±1.5 μM (mean±S.E.M.), which is within the range seen in epileptic patients. Acute experiments with 5, 20 or 100 mg lamotrigine/kg, caused no changes in brain amino acid levels. The results suggest that chronic lamotrigine treatment increases GABAergic activity in the hippocampus. The cerebral increase in taurine, which has neuromodulatory properties, may contribute to the antiepileptic effect of lamotrigine.

Clinical Applications of Capillary Electrophoresis. Stephen M. Palfrey, ed., Totowa, NJ: Humana Press, 1999, 212 pp., $79.50. ISBN 0-89603-639-1.

For clinical laboratories, electrokinetic capillary assays represent an emerging technology whose popularity and importance are increasing steadily. This book brings together for the first time a collection of detailed capillary electrophoresis (CE) protocols for the clinical laboratory. Included are assays for analysis of serum, urinary, and cerebrospinal fluid proteins; hemoglobin variants, DNA fragments associated with certain diseases; serum lamotrigine; drugs of abuse in urine; urinary oxalate and citrate; and plasma nitrite and nitrate. The book tries to give a “representative rather than a comprehensive look” at those assays. Chapters are written in …

Determination of lamotrigine in human serum by liquid chromatography

A rapid high-performance liquid chromatographic method was developed using a short silica column (30 mm×4.6 mm) with an aqueous methanol mobile phase consisting of methanol–water–NH 4H 2PO 4 (94:5.96:0.04) adjusted to a final apparent pH of 5.0 and pumped at a flow-rate of 1 ml/min. Ultraviolet detection was carried out at a wavelength of 280 nm, and serum samples were prepared for HPLC analysis by extraction into dichloromethane after basification. Lamotrigine was eluted at 0.96 min. Within-day variation of the method was 4.46% at 0.75 μg/ml and 2.37% at 6.0 μg/ml, and day-to-day variation was 9.10% at 0.75 μg/ml and 7.28% at 6.0 μg/ml.

Lamotrigine serum concentration-to-dose ratio: influence of age and concomitant antiepileptic drugs and dosage implications.

Using bivariate and multivariate methods, we retrospectively analyzed the influence of patient age and the use of concomitant antiepileptic drugs (AEDs) on the lamotrigine (LTG) concentration-to-dose (C/D) ratio in samples from 164 patients (68 children, 96 adults) with epilepsy receiving LTG alone (n = 28) or in combination with various antiepileptic drugs (n = 136). The LTG C/D ratio increased with age in children receiving LTG alone (r = 0.60, p < 0.01), but decreased with age in adults receiving LTG and inducers (r = -0.42, p < 0.001). In patients receiving LTG and inducers, the ratio was statistically lower in those younger than 9 years of age (0.23 +/- 0.08) and older than 30 years of age (0.32 +/- 0.15) than it was in those between 9 and 30 years of age (0.44 +/- 0.15). The mean LTG C/D ratio was 0.37 +/- 0.15 in patients receiving LTG and inducers (n = 92), 0.84 +/- 0.41 in patients receiving LTG alone (n = 28), 1.09 +/- 0.44 in those receiving LTG with VPA plus inducers (n = 17), and 3.41 +/- 1.18 in those receiving LTG and VPA (n = 27). Differences in the LTG C/D ratio between treatment groups were similar in children and in adults. We reached the following conclusions: The LTG C/D ratio increased with age in children but may decrease with age in adults receiving concomitant enzyme-inducing AEDs; the LTG C/D ratio was 10 times lower in patients receiving LTG and inducers than in those receiving LTG and VPA (in both children and adults), and this difference was higher than the four-fold difference described for LTG half-life and the two-fold differences currently used in LTG dosage.

Analysis of the antiepileptic phenyltriazine compound lamotrigine using gas chromatography with nitrogen phosphorus detection.

A method is described for the determination of lamotrigine in serum or plasma, based on gas chromatography with nitrogen-phosphorus detection. The method requires minimal sample preparation. The drug is extracted from 1.0 ml of serum at pH 11 into butylacetate containing prazepam as internal standard. An aliquot of the organic phase is then injected onto an HP-5 fused silica capillary column and analyzed with temperature programming from 90 degrees to 250 degrees C. Lamotrigine is characterized by a relative retention time of 0.832 (+/-0.03) compared with prazepam. The method is competitive with the reported high-performance liquid chromatography procedures in terms of precision and sensitivity. Coefficients of variation, calculated from the results of between-run reproducibility tests, were 6.7%, 4.6%, 4.8%, and 6.2% for samples spiked with 0.20, 1.21, 2.42 and 10.84 micrograms/ml lamotrigine, respectively. The lower limit of quantitation of the method is 0.15 microgram/ml. The proposed procedure can be integrated easily in a comprehensive toxicology screening.

A rapid cost-effective high-performance liquid chromatographic (HPLC) assay of serum lamotrigine after liquid-liquid extraction and using HPLC conditions routinely used for analysis of barbiturates.

Lamotrigine (lamictal) is a new anticonvulsant drug approved by the FDA for clinical use. Therapeutic monitoring of lamotrigine is useful for patient management and avoidance of toxicity. The suggested therapeutic range is 1 to 4 micrograms/ml. The authors describe a simple high-performance liquid chromatographic (HPLC) method for analysis of lamotrigine from serum. Serum (0.5 ml) was alkalinized with borate buffer (pH 9.8). Lamotrigine and the internal standard thiopental were extracted with 10 ml of chloroform. After evaporation of the extract, the residue was reconstituted in the mobile phase (prepared by mixing 750 ml of potassium dihydrogen phosphate, 550 ml of deionized water, 430 ml of methanol, and 100 microliters of triethylamine as an ion pairing reagent) and injected into an LC-18 column (15 cm x 4.6 mm). The authors use this HPLC system routinely in their laboratory for the analysis of barbiturates. They demonstrated that the same system can be used for the analysis of lamotrigine. The within-run and between-run precisions of the lamotrigine assay were 1.63% (mean = 3.05, SD = 0.05 microgram/ml, n = 6) and 3.7% (mean = 2.97 micrograms/ml, SD = 0.11, n = 8). The assay was linear for serum lamotrigine concentrations of 0.5 microgram/ml to 20 micrograms/ml with a detection limit of 0.5 microgram/ml. The authors observed excellent correlation between serum lamotrigine concentrations measured by their assay and a reference laboratory in six patients receiving lamotrigine. Their assay is free from interferences from common tricyclic antidepressants, benzodiazepines, other common anticonvulsants, salicylate, and acetaminophen.

Optimized high-performance liquid chromatographic method for determination of lamotrigine in serum with concomitant determination of phenytoin, carbamazepine, and carbamazepine epoxide.

Lamotrigine (LG), phenytoin (PY), carbamazepine (CM), and carbamazepine epoxide (CE) are measured with an optimized procedure that uses thin sorbent extraction disks and a highly selective, sterically protected bonded silica high-performance liquid chromatography (HPLC) column. Routinely, serum (200 microliters at pH 6.8 with cyheptamide as internal standard) is applied to an Empore octyl (C8) solid-phase extraction disk to isolate the drugs. a water wash removes interferences, and the retained drugs are eluted with a small volume of solvent. The eluate is directly injected onto a Zorbax Stable Bond cyanopropyl HPLC column with quantification at 214 nm. Evaporation-concentration steps are unnecessary. Overall, for all drugs, between-run precision coefficients of variation (n = 16 each) ranged from 2.1% to 4.9% at concentrations from 0.75 to 20.5 mg/l; extraction recoveries fell within a range of 96% to 110% at concentrations of 2, 10, and 30 mg/l tested for each drug; the lowest limit of detection was 0.15 to 0.35 mg/l. The analytical response was linear for each drug > 80 mg/l (LG) and > 50 mg/l (PY, CM, and CE). Optimization graphs are presented to illustrate the rationale for selection of test parameters for a robust method. In addition, a comparison study between two commercial laboratories demonstrates accuracy problems associated with LG testing.

Lamotrigine analysis in plasma by gas chromatography-mass spectrometry after conversion to a tert.-butyldimethylsilyl derivative.

Lamotrigine (lamictal) is a new anticonvulsant drug recently approved by the FDA for clinical use. Therapeutic monitoring of lamotrigine is useful for patient management (therapeutic range 1-4 microg/ml). Here we describe a gas chromatography-mass spectrometric identification and quantitation of lamotrigine after extraction from human serum and derivatization. Lamotrigine was extracted from alkaline serum with chloroform and derivatized with N-methyl-N-(tert.-butyldimethysilyl) trifluoroacetamide containing 2% tert.-butyldimethylchlorosilane. Oxazepam-d5 was used as an internal standard. The tert.-butyldimethylsilyl derivative of lamotrigine showed distinct molecular ions at m/z 483 and 485 as well as other peaks at m/z 426, 370 and 334 for unambiguous identification. The base peak was observed at m/z 199. Similarly, the tert.-butyldimethysilyl derivative of oxazepam-d5 showed molecular ions at m/z 519 and 521 along with other characteristic peaks at m/z 462, 376 and 318. For the analysis of lamotrigine, the mass spectrometer was operated in the selective ion monitoring mode. The within-run and between-run precisions were 4.3% (mean=3.01, S.D.=0.13 microg/ml) and 5.1% (mean=2.93, S.D.=0.15 microg/ml), respectively at a serum lamotrigine concentration of 3.0 microg/ml. The within-run and between-run precisions were 8.2% (mean=0.49, S.D.=0.04 microg/ml) and 10.6% (mean=0.47, S.D.=0.05 microg/ml), respectively at a serum lamotrigine concentration of 0.5 microg/ml. The assay was linear for serum lamotrigine concentrations of 0.5-20 microg/ml. The detection limit was 0.25 microg/ml. The assay was free from interferences from common tricyclic antidepressants, benzodiazepines, other common anticonvulsants, salicylate and acetaminophen.

Serum lamotrigine analysis by capillary electrophoresis

Lamotrigine, a new antiepileptic drug, is analyzed by capillary zone electrophoresis. Samples were deproteinized with acetonitrile containing an internal standard, acidified with dilute acetic acid and injected into the capillary. The drug migrated rapidly with the cationic compounds in about 3.5 min far from any interfering substances. The test was linear between 0.5-10 mg/l. The analysis time was about 5 min. The CE values correlated well with an HPLC method (r = 0.97; n = 35). The mean serum concentration of 121 patients on this drug was 3.7 mg/l. Incubating the serum with beta-glucuronidase for 1 h increased the peak height of lamotrigine by about 24%.

Lamotrigine analysis in serum by high-performance liquid chromatography.

Lamotrigine is an anticonvulsant drug soon to be introduced to the North American market. It is chemically unrelated to any currently available antiepileptic drug. The objective of this study was to develop a quantitative high-performance liquid chromatography assay for lamotrigine in serum. Lamotrigine was extracted from serum at alkaline pH into ethyl acetate after addition of the internal standard (BW725C78). After mixing, the organic layer was evaporated to dryness before dissolving the residue in methanol for isocratic separation on a RP-8 column (5 microns) with a mobile phase of water/0.5 M phosphate buffer at pH 6.5/acetonitrile (790/10/200) with eluant monitoring at 306 nm. Calibration was performed with five serum standards (2-32 microM and recovery averaged 88% at 25 microM. Between-run precision was 4.1 and 2.5% C.V. at 13.6 and 31.6 microM, respectively. At room temperature, lamotrigine was stable for a minimum of 7 days. Interference studies were performed on serum specimens containing commonly monitored drugs. The only potentially interfering drug was carbamazepine, which elutes 2.5 times longer than lamotrigine. We conclude that this is a reliable method for quantitation of lamotrigine in serum.