Estimation of lithium clearance in patients with bipolar disorder

External Evaluation of Population Pharmacokinetics Models of Lithium in the Bipolar Population

Lithium has been used in the treatment of bipolar disorder for several decades. Treatment optimization is recommended for this drug, due to its narrow therapeutic range and a large pharmacokinetics (PK) variability. In addition to therapeutic drug monitoring, attempts have been made to predict individual lithium doses using population pharmacokinetics (popPK) models. This study aims to assess the clinical applicability of published lithium popPK models by testing their predictive performance on two different external datasets. Available PopPK models were identified and their predictive performance was determined using a clinical dataset (46 patients/samples) and the literature dataset (89 patients/samples). The median prediction error (PE) and median absolute PE were used to assess bias and inaccuracy. The potential factors influencing model predictability were also investigated, and the results of both external evaluations compared. Only one model met the acceptability criteria for both datasets. Overall, there was a lack of predictability of models; median PE and median absolute PE, respectively, ranged from -6.6% to 111.2% and from 24.4% to 111.2% for the literature dataset, and from -4.5% to 137.6% and from 24.9% to 137.6% for the clinical dataset. Most models underpredicted the observed concentrations (7 out of 10 models presented a negative bias). Renal status was included as a covariate of lithium's clearance in only two models. To conclude, most of lithium's PopPK models had limited predictive performances related to the absence of covariates of interest included, such as renal status. A solution to this problem could be to improve the models with methodologies such as metamodeling. This could be useful in the perspective of model-informed precision dosing.

Effect of regulated add-on sodium chloride intake on stabilization of serum lithium concentration in bipolar disorder: A randomized controlled trial

OBJECTIVE

Lithium-induced natriuresis may lead to lithium retention and fluctuation of lithium levels during maintenance therapy. Therefore, the present study was conducted to evaluate the effect of add-on sodium chloride on serum lithium levels in bipolar disorder.

METHODS

This RCT was conducted in 60 patients with type I bipolar disorder who were randomized into the control group that received lithium carbonate with the advice not to take additional salt (at the table) and the test group that received sachets of sodium chloride (1 g/d) as an add-on to lithium carbonate and were advised to restrict their additional salt intake (at the table) to 1 g/d. After baseline assessments, all patients were followed up at 4 weeks, 8 weeks, and 12 weeks when serum lithium, sodium, and potassium were estimated. Serum creatinine and aldosterone were repeated at 12 weeks. The percentage of patients showing fluctuations in serum lithium level (serum lithium <0.6 mEq/L or >0.8 mEq/L) was considered as the primary outcome measure.

RESULTS

In the test group, the fluctuation rate in serum lithium (26.7%) was significantly (p = 0.01) lower than that in the control group (63.3%). Serum lithium values varied significantly across sampling times in the control group but not in the test group. There was a significant difference in serum lithium between the groups at 8 and 12 weeks of follow-up. There were no significant differences in the change in serum sodium, potassium, creatinine, aldosterone, creatinine clearance, and blood pressure within the group and between the groups. A significant positive correlation was found between serum lithium and aldosterone at baseline.

CONCLUSIONS

Intake of add-on sodium chloride (1 gm/day) may reduce the fluctuations in serum lithium during the maintenance phase of lithium therapy in type I bipolar disorder.

GOV IDENTIFIER

NCT04222816.

Lithium replacement dose recommendations using Monte Carlo simulations

OBJECTIVES

Missed medication doses are a common clinical problem, and cause consternation when prescribing lithium because its plasma levels must be kept within a narrow therapeutic window. Therefore, this study set out to determine the potential impact of missed lithium doses on its pharmacokinetics, and to explore the optimal compensatory dosing scheme. This is difficult to determine clinically and in research because of ethical constraints and therefore we modelled the effects using simulations.

METHODS

Monte Carlo simulations were used to simulate lithium concentrations under different missed dose scenarios. For patients with normal renal function, the optimal replacement dosing scheme was selected based on the lowest percentage of deviation from the full adherence scenario. However, for patients with renal impairment the appropriate dosing schedule was selected based on the lowest number of simulated concentrations above the upper range of 1.2 mEq/L.

RESULTS

The impact of a missed lithium dose depended on its daily dose. The higher the daily dose, the higher the deviation from full adherence. In patients with normal renal function, replacement with a regular dose was most appropriate. But in patients with renal impairment, replacement with a partial dose appeared to be most suitable.

CONCLUSIONS

This study has enabled insights into the optimal suitable lithium replacement dosing schemes for patients with normal renal function and renal impairment. These proposed schemes can be used cautiously in clinical practice in conjunction with clinician judgment and can also be used as a basis for future clinical research.

Lamotrigine-induced mania: warning report for the identification of vulnerable populations and expert clinical recommendations for prescription

Lamotrigine (LTG) is an anticonvulsant drug used for the prevention of depressive episodes in bipolar disorder (BD) that might induce manic episodes in some cases. A 38-year-old man, stabilized with asenapine due to a brief psychotic episode, presented depressive symptoms and LTG was titrated up to 200 mg/day in 6 weeks. One week later he was diagnosed with a first manic episode with psychotic symptoms [Young Mania Rating Scale (YMRS = 31)] and type I BD (BD-I). LTG was withdrawn and he was treated with lithium and lurasidone. The episode remitted in 1 week. A 45-year-old woman with BD presented persistent depressive symptoms and received LTG 25 mg/day. After 3 weeks she was diagnosed with a manic episode with psychotic symptoms (YMRS = 35). LTG was suspended and aripiprazole increased. The episode remitted within 10 days. Both patients remained euthymic with no further episodes after 1-year follow-up. The propensity of LTG to induce manic episodes may be related to its lack of antimanic effects, along with its antidepressant properties, probably related to decreased glutamate release. Secondary analyses from LTG randomized clinical trials have excluded subjects with higher vulnerability to manic switches so that the risk of LTG-induced mania might have been underestimated. LTG-induced mania may be more likely to happen in patients with BD-I, manic predominant polarity, an index manic episode, or those with a history of the antidepressant manic switch. Therefore, in BD patients with the aforementioned risk factors, LTG use should be carefully managed: starting with low doses, extending tapering lengths, using adjunctive treatments and close monitoring manic symptoms.

Population Pharmacokinetics and Dosing Regimen of Lithium in Chinese Patients With Bipolar Disorder

Background: Lithium is an effective medication approved for the treatment of bipolar disorder (BD). It has a narrow therapeutic index (TI) and requires therapeutic drug monitoring. This study aimed to conduct a population pharmacokinetics (PPK) analysis of lithium and investigate the appropriateness of the dosing regimen according to different patient characteristics.

Methods: A total of 476 lithium concentrations from 268 patients with bipolar disorder were analyzed using nonlinear mixed-effects modeling. Monte Carlo simulations were employed to investigate the influence of covariates, such as weight, creatinine clearance, and daily doses of lithium concentrations, and to determine the individualized dosing regimens for patients.

Results: Lithium PK was described by a one-compartment model with first-order absorption and elimination processes. The typical estimated apparent clearance was 0.909 L/h⁻¹ with 16.4% between-subject variability in the 62 kg patients with 116 ml/min creatinine clearance and 600 mg daily doses. To achieve a target trough concentration (0.4–0.8 mmol/L) in the maintenance phase, the regimen of 500 mg than 750 mg daily dose was recommended for patients with renal insufficiency and weighing 100 kg.

Conclusion: A PPK model for lithium was developed to determine the influence of patient characteristics on lithium pharmacokinetics. Weight, creatinine clearance, and total daily dose of lithium can affect the drug’s clearance. These results demonstrate the nonlinear renal excretion of lithium; hence, dosage adjustments are recommended for patients with renal insufficiency.

Therapeutic Interventions to Mitigate Mitochondrial Dysfunction and Oxidative Stress–Induced Damage in Patients with Bipolar Disorder

Bipolar disorder (BD) is characterized by mood changes, including recurrent manic, hypomanic, and depressive episodes, which may involve mixed symptoms. Despite the progress in neurobiological research, the pathophysiology of BD has not been extensively described to date. Progress in the understanding of the neurobiology driving BD could help facilitate the discovery of therapeutic targets and biomarkers for its early detection. Oxidative stress (OS), which damages biomolecules and causes mitochondrial and dopamine system dysfunctions, is a persistent finding in patients with BD. Inflammation and immune dysfunction might also play a role in BD pathophysiology. Specific nutrient supplements (nutraceuticals) may target neurobiological pathways suggested to be perturbed in BD, such as inflammation, mitochondrial dysfunction, and OS. Consequently, nutraceuticals may be used in the adjunctive treatment of BD. This paper summarizes the possible roles of OS, mitochondrial dysfunction, and immune system dysregulation in the onset of BD. It then discusses OS-mitigating strategies that may serve as therapeutic interventions for BD. It also analyzes the relationship between diet and BD as well as the use of nutritional interventions in the treatment of BD. In addition, it addresses the use of lithium therapy; novel antipsychotic agents, including clozapine, olanzapine, risperidone, cariprazine, and quetiapine; and anti-inflammatory agents to treat BD. Furthermore, it reviews the efficacy of the most used therapies for BD, such as cognitive–behavioral therapy, bright light therapy, imagery-focused cognitive therapy, and electroconvulsive therapy. A better understanding of the roles of OS, mitochondrial dysfunction, and inflammation in the pathogenesis of bipolar disorder, along with a stronger elucidation of the therapeutic functions of antioxidants, antipsychotics, anti-inflammatory agents, lithium therapy, and light therapies, may lead to improved strategies for the treatment and prevention of bipolar disorder.