Trends and changes in the clinical use of lamotrigine

Simultaneous determination of plasma lamotrigine, lamotrigine N2-glucuronide and lamotrigine N2-oxide by UHPLC-MS/MS in epileptic patients

The plasma concentration of lamotrigine (LTG) and its metabolites has great interindividual variability. An UHPLC-MS/MS method for simultaneous determination of LTG and lamotrigine N2-glucuronide (LTG N2-GLUC), lamotrigine N2-oxide was developed, validated, and applied in 58 plasma samples. The ion transition was m/z 256.0 > 144.9 for LTG, 432.1 > 256.0 for LTG N2-GLUC, 272.2 > 241.9 for LTG N2-oxide, and 259.1 > 144.8 for LTG-¹³C₃ (internal standard). The flow rate was 0.4 mL/min with a run time of 3 min. The calibration range was 0.025-2 mg/L for LTG and LTG N2-GLUC, and 0.000625-0.05 mg/L for LTG N2-oxide. For all analytes, the intra-day and inter-day bias and imprecision were -11.7-5.7 % and less than 14.3 %, and the internal standard normalized recovery and matrix factor were 91.7-101.5 % and 98.1-110.1 % with CV < 13. 7%. Ten- and twenty-fold dilution with blank plasma did not affect the analysis. All analytes were stable in plasma at room temperature for 8 h, at -80 °C for 80 days, and after 3 freeze-thaw cycles. The LTG N2-GLUC/LTG ratio was 0.44 in LTG monotherapy group. The ratio was reduced to 0.17 when co-administrated with valproic acid, while elevated to 0.82 when co-administrated with enzyme inducer. In conclusion, this method is suitable for simultaneous determination of LTG, LTG N2-GLUC and LTG N2-oxide in human plasma.

Long-term follow-up with therapeutic drug monitoring of antiepileptic drugs in patients with juvenile myoclonic epilepsy

BACKGROUND AND PURPOSE

Patients with juvenile myoclonus epilepsy (JME) may experience uncontrolled seizures and challenges regarding adherence. Implementation of therapeutic drug monitoring (TDM) may contribute to individualization of the therapy with antiepileptic drugs (AEDs). The purpose of this study was to investigate how the treatment of patients with JME is monitored and to demonstrate pharmacokinetic variability within and between patients with a long-term TDM approach.

METHOD

Retrospective data from patients with JME from the TDM-database at Drammen Hospital and the National Center for Epilepsy in Norway (2007-2018) were included.

RESULTS

Data from 80 of 90 patients with JME using AEDs with TDM measurements was included (88%, 49/31 women/men aged 14-39). One third (27, 33%) was seizure free, 19 (24%) had generalized tonic-clonic seizures, and 53 (66%) myoclonic seizures during the last year. The most common AEDs measured included lamotrigine, valproate, and levetiracetam. Long-term TDM demonstrated variability over time expressed as intra-patient median values and inter-patient ranges of 19% (7-47) for valproate, 43% (10-83) for lamotrigine and 35% (6-111) for levetiracetam. Fifteen pecent (83/563) of serum concentrations were below the reference ranges and clould be due to variable adherence. Comedication with valproate for lamotrigine and pregnancy contributed to variability. The applicability is illustrated in a case of 10 years' follow-up in a young woman.

CONCLUSION

There was extensive pharmacokinetic variability of AEDs in and between patients with JME. A long-term TDM approach may contribute to closer monitoring of patients with JME and be used as a practical tool during clinical consultations.

Relationship Between UGT1A4 and UGT2B7 Polymorphisms and the Steady-State Plasma Concentrations of Lamotrigine in Patients With Treatment-Resistant Depressive Disorder Receiving Lamotrigine as Augmentation Therapy

BACKGROUND

In a previous study, the authors had shown that in treatment-resistant depressive disorder, an early therapeutic response to lamotrigine augmentation therapy is dependent on its plasma concentrations. Lamotrigine is mainly metabolized by UGT1A4 and UGT2B7, and polymorphisms of said UGTs that affect enzyme activities have been reported. This study investigated the effect of these polymorphisms on the steady-state plasma concentrations (Css) of lamotrigine in patients with treatment-resistant depressive disorder receiving lamotrigine as augmentation therapy.

METHODS

The subjects were 103 depressed patients who had already shown insufficient response to at least 3 psychotropics including antidepressants, mood stabilizers, and atypical antipsychotics. The diagnoses were major depressive disorder (n = 46), bipolar II disorder (n = 44), and bipolar I disorder (n = 13). They received augmentation therapy with lamotrigine for 8 weeks. The final doses of lamotrigine were 100 mg/d for 67 subjects who were not taking valproate and 75 mg/d for 36 subjects taking valproate, respectively. Blood sampling was performed at the 8th week. Plasma concentrations of lamotrigine were measured by high-performance liquid chromatography. The genotypes of UGT1A4 142T>G, UGT2B7 -161C>T, and UGT2B7 372A>G were identified by polymerase chain reaction analyses.

RESULTS

There were no significant relationships between these polymorphisms and the Css of lamotrigine in the subjects regardless of valproate comedication.

CONCLUSIONS

This study suggests that these genetic polymorphisms do not affect the Css of lamotrigine in patients with treatment-resistant depressive disorder receiving lamotrigine as augmentation therapy.

Reference ranges for antiepileptic drugs revisited: a practical approach to establish national guidelines

BACKGROUND AND OBJECTIVE

Laboratories sometimes use different reference ranges for the same antiepileptic drug (AED), particularly for new and poorly investigated drugs. This may contribute to misunderstandings, concerns or inappropriate dose changes, which in turn may affect therapeutic effect, drug safety or treatment adherence. Therefore, the Norwegian Association of Clinical Pharmacology wished to update and harmonize the reference ranges for AEDs and establish national guidelines for Norway.

METHODS

A working group collected information on the reference ranges used by Norwegian laboratories for all commonly used AEDs. These reference ranges were compared to recent recommendations by the International League Against Epilepsy, current literature, applicable clinical studies, reference ranges used by leading Northern European epilepsy centers outside of Norway, and routine data derived from Norwegian laboratory databases.

RESULTS

Reference ranges varied between laboratories for four of 23 available AEDs (lamotrigine, valproate, eslicarbazepine and oxcarbazepine). For four AEDs (brivaracetam, perampanel, stiripentol and sulthiame), reference ranges had not previously been established. In total, 13 reference ranges were either harmonized, updated or newly established. No changes were applied to the remaining 10 AEDs.

CONCLUSION

Updated and harmonized reference ranges are now available for 22 of the 23 AEDs available in Norway. The exception is vigabatrin (reference range not applicable). Revision of reference ranges is an important part of pharmacovigilance of AEDs and must be a continuous process based on current literature and clinical experience.

Prediction of an Optimal Dose of Lamotrigine for Augmentation Therapy in Treatment-Resistant Depressive Disorder From Plasma Lamotrigine Concentration at Week 2

BACKGROUND

The authors have previously shown that an early therapeutic response to lamotrigine augmentation therapy is dependent on its plasma concentration and that a plasma lamotrigine concentration of 12.7 μmol/L may be a threshold for a good therapeutic response in treatment-resistant depressive disorder. The present study investigated whether or not an optimal dose of lamotrigine could be predicted from plasma lamotrigine concentration at week 2.

METHODS

The subjects were 37 depressed patients who had already shown insufficient response to at least 3 psychotropics including antidepressants, mood stabilizers, and atypical antipsychotics. The diagnoses were major depressive disorder (n = 15), bipolar I disorder (n = 6), and bipolar II disorder (n = 16). They received augmentation therapy with lamotrigine for 8 weeks. The final doses of lamotrigine were 100 mg/d for 16 subjects who were not taking valproate and 75 mg/d for 21 subjects taking valproate, respectively. Blood sampling was performed at weeks 2 and 8. Plasma concentrations of lamotrigine were measured by high-performance liquid chromatography.

RESULTS

There were significant linear relationships between the plasma lamotrigine concentrations at week 2 (x) and those at week 8 (y) for subjects who were not taking valproate (P < 0.01) and those taking valproate (P < 0.01). Regression equations were y = 2.032x + 2.549 for the former and y = 3.599x + 5.752 for the latter, respectively. Based on the equations, a nomogram to estimate an optimal dose of lamotrigine could be calculated.

CONCLUSIONS

The present study suggests that an optimal dose of lamotrigine for augmentation therapy in treatment-resistant depressive disorder can be predicted from a plasma lamotrigine concentration at week 2.

Identifying the incidence of rash, Stevens-Johnson syndrome and toxic epidermal necrolysis in patients taking lamotrigine: a systematic review of 122 randomized controlled trials

Lamotrigine is an antiepileptic drug used for the treatment of epilepsy, bipolar disorder and numerous off-label uses. The development of rash significantly affects its use. The most concerning of these adverse reactions is Stevens-Johnson syndrome/toxic epidermal necrolysis. We performed a systematic review of randomized controlled trials using lamotrigine as a monotherapy to quantify the incidence of cutaneous reactions, particularly Stevens-Johnson syndrome/toxic epidermal necrolysis. Of a total of 4,364 papers regarding lamotrigine, 122 studies met our inclusion and exclusion criteria. In total, 18,698 patients were included with 1,570 (8.3%) of patients experiencing an adverse dermatologic reaction. The incidence of Stevens-Johnson syndrome/toxic epidermal necrolysis was 0.04%.

Relationship between plasma concentrations of lamotrigine and its early therapeutic effect of lamotrigine augmentation therapy in treatment-resistant depressive disorder

BACKGROUND

The relationship between plasma concentrations of lamotrigine and its therapeutic effects was prospectively studied on 34 (9 men and 25 women) inpatients with treatment-resistant depressive disorder during an 8-week treatment of lamotrigine augmentation using an open-study design.

METHODS

The subjects were depressed patients who had already shown insufficient response to at least 3 psychotropics, including antidepressants, mood stabilizers, and atypical antipsychotics. The diagnoses were major depressive disorder (n = 12), bipolar I disorder (n = 7), and bipolar II disorder (n = 15). The final doses of lamotrigine were 100 mg/d for 18 subjects who were not taking valproate and 75 mg/d for 16 subjects taking valproate. Depressive symptoms were evaluated by the Montgomery Åsberg Depression Rating Scale (MADRS) before and after the 8-week treatment. Blood sampling was performed at week 8. Plasma concentrations of lamotrigine were measured by high-performance liquid chromatography.

RESULTS

There was a significant linear relationship between the plasma concentrations of lamotrigine and percentage improvements at week 8 (r = 0.418, P < 0.05). A stepwise multiple regression analysis showed that plasma lamotrigine concentrations alone had a significant effect on the percentage improvements at week 8 (standardized partial correlation coefficients = 0.454, P < 0.001). The receiver operating characteristics analysis indicated that a plasma lamotrigine concentration of 12.7 μmol/L or greater was significantly (P < 0.001) predictive of response (50% or more reduction in the MADRS score). The proportion of the responders was significantly higher in the groups with a lamotrigine concentration >12.7 μmol/L (11/15 versus 4/19, P < 0.01).

CONCLUSIONS

The present study suggests that an early therapeutic response to lamotrigine is dependent on its plasma concentration and that a plasma lamotrigine concentration of 12.7 μmol/L may be a threshold for a good therapeutic response in treatment-resistant depressive disorder.

Trends in pharmacotherapy in patients referred to a bipolar specialty clinic, 2000-2011

OBJECTIVE

To assess mood stabilizer (MS) and second-generation antipsychotic (SGA) prescribing trends in bipolar disorder (BD) outpatients referred to a bipolar disorder specialty clinic over the past 12 years.

METHOD

BD outpatients referred to the Stanford University Bipolar Disorder Clinic during 2000-2011 were assessed with the Systematic Treatment Enhancement Program for BD (STEP-BD) Affective Disorders Evaluation. Prescription rates for MSs and SGAs were compared during the first (2000-2005) and second (2006-2011) six years.

RESULTS

Among 597 BD patients (mean±SD age 35.4±8.6 years; 58.1% female; 40.7% Type I, 43.6% Type II, and 15.7% Type Not Otherwise Specified; taking 2.6±1.7 prescription psychotropic medications), lamotrigine, quetiapine, and aripiprazole usage more than doubled, from 14.7% to 37.2% (p<0.0001), 7.2% to 19.7% (p<0.0001), and 3.1% to 10.9% (p=0.0003), respectively, while olanzapine and risperidone use decreased by more than half from 15.0% to 6.6% (p=0.0043), and from 8.7% to 3.8% (p=0.039), respectively. SGA use increased from 34.1% to 44.8% (p=0.013), although MS use continued to be more common (in 65.2% for 2006-2011). Use of other individual MSs and SGAs and MSs as a class did not change significantly.

CONCLUSIONS

Over 12 years, in patients referred to a BD specialty clinic, lamotrigine, quetiapine, and aripiprazole use more than doubled, and olanzapine and risperidone use decreased by more than half. Tolerability (for lamotrigine, aripiprazole, olanzapine, and risperidone) more than efficacy (for quetiapine) differences may have driven these findings. Additional studies are needed to explore the relative influences of enhanced tolerability versus efficacy upon prescribing practices in BD patients.

Pharmacokinetic variability of four newer antiepileptic drugs, lamotrigine, levetiracetam, oxcarbazepine, and topiramate: a comparison of the impact of age and comedication

BACKGROUND

Newer antiepileptic drugs (AEDs) are widely used in patients with epilepsy. There is still insufficient documentation regarding pharmacokinetic variability of these AEDs in different patient groups.

PURPOSE

The purpose of this study was to compare age and comedication as factors contributing to pharmacokinetic variability between 4 newer AEDs (lamotrigine, levetiracetam, oxcarbazepine, and topiramate) among patients with refractory epilepsy.

METHODS

Data regarding age, gender, use of AEDs, daily doses, and serum concentration measurements were retrieved from a therapeutic drug monitoring database, from patients admitted to the National Center for Epilepsy, Norway, 2007-2008.

RESULTS

In total, 1050 patients were included, 111 younger children (2-9 years), 137 older children (10-17 years), 720 adults (18-64 years), 82 elderly (65-93 years). Fifty percent of the patients were prescribed polytherapy, in 88 different combinations. The interindividual pharmacokinetic variability was extensive, as illustrated by a 10-fold variability in serum concentration compared with dose. Age affected the apparent clearance of levetiracetam to the largest extent, as shown by a 60% increase in younger children and a 40% reduction in the elderly, respectively, compared with adults. Comedication altered the clearance of lamotrigine to the greatest extent ±70% because it is affected by both enzyme inducers and inhibitors. Hepatic enzyme inducers increased the clearance of levetiracetam and topiramate by 25% and oxcarbazepine by 75%. Valproic acid reduced the clearance of topiramate by 25%.

CONCLUSION

Age and comedication are important contributors to pharmacokinetic variability. Age had the greatest impact on levetiracetam, and comedication affected the clearance of each of the 4 AEDs investigated in this study. Pharmacokinetic drug interactions must be carefully considered when multidrug therapies are prescribed. Therapeutic drug monitoring is a valuable tool for individualizing AED therapy.