Single dose pharmacokinetic study of lithium in Taiwanese/Chinese bipolar patients

The increasing challenge of the possible impact of ethnicity on psychopharmacology

Ethnic differences may significantly influence the outcome of psychopharmacological treatment, in terms of prescription, adherence, clinical response, emergence of side effects, as well as pharmacokinetics and pharmacodynamics. The purpose of this review was to explore the available literature in order to provide general suggestions to help clinicians in choosing the best therapeutic option for patients, taking into account ethnicity. Although findings are sometimes controversial, the overall published studies suggest that ethnicities other than Caucasians tend to show a lower response to antidepressants and a reduced compliance. Africans tend to be more prescribed with antipsychotics, probably due to cultural stereotypes, except with clozapine, probably for their chronic benign neutropenia. Asians usually require less antipsychotic dosages than Caucasians. The differential response and side effect profile of antidepressants and antipsychotics have been related to individual intrinsic factors, to genetic make-up, but also to cultural and contextual variables. Interestingly, albeit limited data suggest ethnic-related genetic heterogeneity at the level of the serotonin transporters, the cytochromes and some neuroreceptors. Taken together, no conclusive findings are available about the role and impact of ethnicity in psychopharmacology. One of the main problems is that the majority of the studies in psychopharmacology have been conducted on Caucasians, so that there is an urgent need to have data in other populations. Furthermore, in the era of precision medicine, the role of ethnicity may be also supported by genetic analysis.

A Review for Lithium: Pharmacokinetics, Drug Design, and Toxicity

Lithium as a mood stabilizer has been used as the standard pharmacological treatment for Bipolar Disorder (BD) for more than 60 years. Recent studies have also shown that it has the potential for the treatment of many other neurodegenerative disorders, including Alzheimer's, Parkinson's and Huntington's disease, through its neurotrophic, neuroprotective, antioxidant and anti-inflammatory actions. Therefore, exploring its pharmacokinetic features and designing better lithium preparations are becoming important research topics. We reviewed many studies on the pharmacokinetics, drug design and toxicity of lithium based on recent relevant research from PubMed, Web of Science, Elsevier and Springer databases. Keywords used for searching references were lithium, pharmacology, pharmacokinetics, drug design and toxicity. Lithium is rapidly and completely absorbed from the gastrointestinal tract after oral administration. Its level is initially highest in serum and then is evidently redistributed to various tissue compartments. It is not metabolized and over 95% of lithium is excreted unchanged through the kidney, but different lithium preparations may have different pharmacokinetic features. Lithium has a narrow therapeutic window limited by various adverse effects, but some novel drugs of lithium may overcome these problems. Various formulations of lithium have the potential for treating neurodegenerative brain diseases but further study on their pharmacokinetics will be required in order to determine the optimal formulation, dosage and route of administration.

Population pharmacokinetic modeling of sustained release lithium in the serum, erythrocytes and urine of patients with bipolar disorder

PURPOSE

Lithium (Li), the first-line treatment of bipolar disorder, was first developed as an immediate-release form with a routine therapeutic drug monitoring 12 h after the last dose. In Europe, the most commonly prescribed form is a sustained release (srLi). Yet no pharmacokinetics (PK) study has been published of srLi, administered once a day, in adults. The present study describes srLi PK in the serum and erythrocytes of bipolar patients.

METHODS

To assess srLi PK, we studied prospectively 17 French bipolar patients on a median dose of 1000 mg (600-1600) for at least 2 years. Serum (S), erythrocyte (E) concentrations, and urinary (U) amount were collected over 8 h after 15 days of morning intake using monitoring electronic medical system (MEMs). Population PK parameters were estimated using the SAEM algorithm (MONOLIX 4.3.3 software).

RESULTS

Using a population approach, we built a PK population model of srLi including one S compartment (V_S = 23.0 L, Cl_S = 1.21 L h^-1), one E compartment (V_E = 64.7 L, Cl_SE = 3.63 L h^-1, Cl_ES = 9.46 L h^-1), and one U compartment (F = 0.62) and estimate the ratio of concentrations to Li in E over S at 0.38 with 27% between-subject variability.

CONCLUSION

This is a PK model of srLi once a day in bipolar patients using a population approach simultaneously describing Li concentrations in serum, erythrocytes, and urine which provide an estimate of the ratio of concentration in erythrocyte over serum and its between-subject variability (BSV).

Ethnopsychopharmacology considerations for Asians and Asian Americans

Asians comprise more than 60% of the world's population and are the fastest growing minority group in the United States. Today's psychiatrist must learn to recognize and appreciate the unique factors that influence mental health outcomes in this group. Asian Americans are affected by psychiatric disorders at similar rates as non-Asians, but are significantly underrepresented in psychiatric clinics. When Asians and Asian Americans do present for psychiatric treatment, they often do so with higher severity of illness, and variable levels of compliance. Studies over the past three decades have suggested that pharmacokinetic and pharmacodynamic profiles of various psychotropic medications may be different in Asians, leading to differences in dosage requirements and side-effect profiles. These variations appear to be largely determined by genetic predisposition, but are also influenced by other factors such as environment, social support, cultural perceptions, and physicians' prescribing habits. In this paper, we provide an overview of biological and socio-cultural issues as they relate to psychopharmacology in Asians and Asian Americans, with the hope that a better understanding of these issues will lead to improved mental health care delivery to this population both in the United States, as well as in Asian countries.

Lithium: updated human knowledge using an evidence-based approach. Part II: Clinical pharmacology and therapeutic monitoring

After a single dose, lithium, usually given as carbonate, reaches a peak plasma concentration at 1.0-2.0 hours for standard-release dosage forms, and 4-5 hours for sustained-release forms. Its bioavailability is 80-100%, its total clearance 10-40 mL/min and its elimination half-life is 18-36 hours. Use of the sustained-release formulation results in 30-50% reductions in peak plasma concentrations without major changes in the area under the plasma concentration curve. Lithium distribution to the brain, evaluated using 7Li magnetic resonance spectroscopy, showed brain concentrations to be approximately half those in serum, occasionally increasing to 75-80%. Brain concentrations were weakly correlated with serum concentrations. Lithium is almost exclusively excreted via the kidney as a free ion and lithium clearance is considered to decrease with aging. No gender- or race-related differences in kinetics have been demonstrated. Renal insufficiency is associated with a considerable reduction in renal clearance of lithium and is considered a contraindication to its use, especially if a sodium-poor diet is required. During the last months of pregnancy, lithium clearance increases by 30-50% as a result of an increase in glomerular filtration rate. Lithium also passes freely from maternal plasma into breast milk. Numerous kinetic interactions have been described for lithium, usually involving a decrease in the drug's clearance and therefore increasing its potential toxicity. Clinical pharmacology studies performed in healthy volunteers have investigated a possible effect of lithium on cognitive functions. Most of these studies reported a slight, negative effect on vigilance, alertness, learning and short-term memory after long-term administration only. Because of the narrow therapeutic range of lithium, therapeutic monitoring is the basis for optimal use and administration of this drug. Lithium dosages should be adjusted on the basis of the serum concentration drawn (optimally) 12 hours after the last dose. In patients receiving once-daily administration, the serum concentration at 24 hours should serve as the control value. The efficacy of lithium is clearly dose-dependent and reliably correlates with serum concentrations. It is now generally accepted that concentrations should be maintained between 0.6 and 0.8 mmol/L, although some authors still favour 0.8-1.2 mmol/L. With sustained-release preparations, and because of the later peak of serum lithium concentration, it is advised to keep serum concentrations within the upper range (0.8-1 mmol/L), rather than 0.6-0.8 mmol/L for standard formulations. It is controversial whether a reduced concentration is required in elderly people. The usual maintenance daily dose is 25-35 mmol (lithium carbonate 925-1300 mg) for patients aged <40 years; 20-25 mmol (740-925 mg) for those aged 40-60 years; and 15-20 mmol (550-740 mg) for patients aged >60 years. The initial recommended dose is usually 12-24 mmol (450-900 mg) per day, depending on age and bodyweight. The classical administration schedule is two or three times daily, although there is no strong evidence in favour of a three-times-daily schedule, and compliance with the midday dose is questionable. With a modern sustained-release preparation, the twice-daily schedule is well established, although one single evening dose is being recommended by a number of expert panels.

Ethnicity and psychopharmacology

Ethnicity is reported to be an important, but often ignored factor in psychopharmacology. However, recent advances in molecular biology and the vision of 'personalised medicine' have spurred a debate on the role of ethnicity in this field. This paper reviews literature on the role of race and ethnicity in psychopharmacology. Despite considerable controversy on what the concepts of ethnicity and race actually measure, they are considered as important proxies for a person's culture, diet, beliefs, health behaviours and societal attitudes. Research has shown ethnic differences in the clinical presentation, treatment, clinical response and outcome of mental illnesses. A number of ethnically specific variations have been found in the genetic and non-genetic mechanisms affecting pharmacokinetics and dynamics of psychotropic drugs, which might underlie the previously mentioned differences in drug use and response across ethnicities. Although some of these ethnic differences could be partially explained by genetic factors, a number of ethnically based variables like culture, diet and societal attitudes could potentially have a significant, but as yet unquantified influence as well. Future research needs to address the problems with defining and accurately measuring 'ethnicity', as well as focus upon conducting studies that could guide treatments for people from diverse backgrounds.

A review and assessment of potential sources of ethnic differences in drug responsiveness

The International Conference on Harmonization (ICH) E5 guidelines were developed to provide a general framework for evaluating the potential impact of ethnic factors on the acceptability of foreign clinical data, with the underlying objective to facilitate global drug development and registration. It is well recognized that all drugs exhibit significant inter-subject variability in pharmacokinetics and pharmacologic response and that such differences vary considerably among individual drugs and depend on a variety of factors. One such potential factor involves ethnicity. The objective of the present work was to perform an extensive review of the world literature on ethnic differences in drug disposition and responsiveness to determine their general significance in relation to drug development and registration. A few examples of suspected ethnic differences in pharmacokinetics or pharmacodynamics were identified. The available literature, however, was found to be heterologous, including a variety of study designs and research methodologies, and most of the publications were on drugs that were approved a long time ago.