Clinical experience combined with therapeutic drug monitoring of lacosamide

Pharmacological aspects of antiseizure medications: From basic mechanisms to clinical considerations of drug interactions and use of therapeutic drug monitoring

Antiseizure medications (ASMs) are the cornerstone of treatment for patients with epilepsy. Several new ASMs have recently been introduced to the market, making it possible to better tailor the treatment of epilepsy, as well as other indications (psychiatry and pain disorders). For this group of drugs there are numerous pharmacological challenges, and updated knowledge on their pharmacodynamic and pharmacokinetic properties is, therefore, crucial for an optimal treatment outcome. This review focuses on educational approaches to the following learning outcomes as described by the International League Against Epilepsy (ILAE): To demonstrate knowledge of pharmacokinetics and pharmacodynamics, drug interactions with ASMs and with concomitant medications, and appropriate monitoring of ASM serum levels (therapeutic drug monitoring, TDM). Basic principles in pharmacology, pharmacokinetic variability, and clinically relevant approaches to manage drug interactions are discussed. Furthermore, recent improvements in analytical technology and sampling are described. Future directions point to the combined implementation of TDM with genetic panels for proper diagnosis, pharmacogenetic tests where relevant, and the use of biochemical markers that will all contribute to personalized treatment. These approaches are clinically relevant for an optimal treatment outcome with ASMs in various patient groups.

Lacosamide effectiveness and tolerability in patients with drug-resistant epilepsy and severe disability under polytherapy: Therapy optimization as emerging from an observational study

OBJECTIVE

We explored the efficacy and safety of lacosamide combined with inhibitors of fast-inactivated sodium channels or with other antiepileptic drugs, in patients with drug refractory focal epilepsy associated with intellectual or psychiatric disability.

METHODS

Observational study of lacosamide including the monitoring of lacosamide trough plasma levels and of electroencephalograms.

RESULTS

We followed up 44 patients from the start of lacosamide therapy for up to 3 years, with a clinical, electroencephalogram (EEG), and pharmacological follow-up. Median patients' age was 32.7 years, median age at epilepsy onset was 3.5 years. Intellectual disability was severe in 55.4% of the cohort and drug refractoriness was diagnosed in 88.6% of patients, who had predominantly focal seizures (80%). The severity of their epilepsy was suggested by the use of combined therapies with non-sodium blockers and sodium blockers in 75% of patients. Lacosamide was added to previous therapies and up-titrated to a median of 300 mg/d. Lacosamide add-on led to simplification of the previous drug regimen with a dose reduction in 87.9% of users of sodium blockers and in 66.7% of users of non-sodium blockers, and to withdrawal of previously administered sodium blockers in 48.5% users and non-sodium blockers in 47.6% users. Lacosamide was prescribed at lower doses in the presence of oxcarbazepine (p = 0.029), lamotrigine (p = 0.015), and topiramate (p < 0.001). Mean lacosamide plasma levels were 6.0 ± 2.4 mg/L; they were in linear correlation with the administered dose (R² = 0.38, p < 0.001) and were influenced by the association with lamotrigine (p = 0.008), zonisamide (p = 0.012), and clobazam (p = 0.028). Lacosamide combination regimens led to an average reduction of 42% in baseline seizure frequency, with 50% patients reporting ≥50% seizure frequency reduction. Efficacy was directly correlated with lacosamide dose (R² = 0.47, p < 0.001, B = 0.53) and trough plasma levels (R² = 0.31, p < 0.001, B = 0.16). Electroencephalogram profiles were improved in 40.9% of patients and EEG improvement was not significantly correlated with seizure frequency reduction. Lacosamide safety was good, with 37 adverse reactions in 30 patients, of which 50% were attributed to lacosamide and led to lacosamide withdrawal in 18% of cases. The retention rate of lacosamide was of 88.6% at 1 year, 86.4% at 2 years, and 72.7% after three years. The severity of intellectual disability was directly correlated with increased possibility of lacosamide retention (OR = 0.46 per severity tier, p = 0.016).

CONCLUSION

Lacosamide add-on allowed dose reduction of previous therapies and reduced the frequency of seizures, showing good tolerability even at high doses, without exceeding reference plasma levels.

Therapeutic Monitoring of Lacosamide in Japanese Patients With Epilepsy: Clinical Response, Tolerability, and Optimal Therapeutic Range

BACKGROUND

Lacosamide is a novel anticonvulsant that acts by enhancing sodium channel slow inactivation. The aims of this study were to evaluate the influence of concomitant antiepileptic drugs (AEDs) on serum lacosamide concentration and explore the relationship between lacosamide serum concentration and both clinical response and adverse effects.

METHODS

The authors analyzed 649 serum samples from 426 Japanese patients with epilepsy. The concentration-to-dose (CD) ratio of lacosamide was compared among patients on various AED regimens. Clinical information about seizure frequency and adverse events was obtained from clinical records.

RESULTS

In patients who did not receive enzyme-inducing AEDs, the CD ratio (mean ± SD) of lacosamide was 1.84 ± 0.68. By contrast, the CD ratio in patients who received phenytoin, carbamazepine, and phenobarbital was 1.42 ± 0.66 (22.8% lower), 1.46 ± 0.40 (20.7% lower), and 1.36 ± 0.38 (26.1% lower), respectively. Seventy-four patients (17.3%) achieved >50% seizure reduction. The median lacosamide concentration in patients who received and did not receive a sodium channel blocker was 6.6 mcg/mL (26.4 μmol/L) and 8.4 mcg/mL (33.6 μmol/L), respectively. Adverse events, including dizziness, somnolence, diplopia, and anorexia, were reported by 70 patients (16.4%). The incidence rate in patients treated with sodium channel blockers was significantly higher than that in patients not treated with these drugs (21.1% vs. 10.3%; P < 0.005), and the median lacosamide concentration in these patient groups was 5.1 (20.4 μmol/L) and 7.5 mcg/mL (30 μmol/L), respectively.

CONCLUSIONS

Therapeutic drug monitoring of lacosamide is clinically useful because it allows physicians to estimate the extent of drug interactions and adjust the dose in individual AED regimens.