Brain lithium concentrations measured with lithium-7 magnetic resonance spectroscopy in patients with affective disorders: relationship to erythrocyte and serum concentrations

Determination of lithium concentration in capillary blood using volumetric dried blood spots

BACKGROUND

Lithium is a cornerstone in the treatment of bipolar disorder and is considered one of the most effective treatments in psychiatry at large. Lithium treatment requires individual dosing with frequent serum concentration measurements due to the narrow therapeutic window and risk of toxicity. There is need for patient-centric methods for lithium monitoring and the use of dried blood spots has recently been proposed for determination of lithium concentration. The purpose of the current study was to assess feasibility of this method by introducing a volumetric technique developed for home-sampling.

MATERIALS AND METHODS

Laboratory: Capillary blood was sampled by finger-prick using a volumetric device that collects 10 µL volumes as a dried blood spot. Lithium was measured in the dried blood spots using a validated atomic absorption spectroscopy method.

CLINICAL

Thirty-nine lithium-treated patients were recruited, and dried blood spots and venous blood samples were collected. Routine serum analysis was performed for comparison.

RESULTS

The range of serum lithium concentrations was 0.41-1.22 mmol/L, and the dried blood spot/serum ratio was 0.78. A strong linear correlation between the two specimens was shown with Pearson's R = 0.95 (r² = 0.90). Adding hematocrit as a variable only minimally improved prediction.

CONCLUSION

Volumetric dried blood spots is a promising technique for measurement of lithium concentrations. This will enable home-sampling and could potentially save resources, improve compliance, and make treatment safer. This may facilitate the use of lithium treatment in regions where monitoring via venous blood sampling remains difficult. However, the usability of dried blood spots for monitoring lithium treatment longitudinally remains to be examined.

The Role of Mitonuclear Incompatibility in Bipolar Disorder Susceptibility and Resilience Against Environmental Stressors

It has been postulated that mitochondrial dysfunction has a significant role in the underlying pathophysiology of bipolar disorder (BD). Mitochondrial functioning plays an important role in regulating synaptic transmission, brain function, and cognition. Neuronal activity is energy dependent and neurons are particularly sensitive to changes in bioenergetic fluctuations, suggesting that mitochondria regulate fundamental aspects of brain function. Vigorous evidence supports the role of mitochondrial dysfunction in the etiology of BD, including dysregulated oxidative phosphorylation, general decrease of energy, altered brain bioenergetics, co-morbidity with mitochondrial disorders, and association with genetic variants in mitochondrial DNA (mtDNA) or nuclear-encoded mitochondrial genes. Despite these advances, the underlying etiology of mitochondrial dysfunction in BD is unclear. A plausible evolutionary explanation is that mitochondrial-nuclear (mitonuclear) incompatibility leads to a desynchronization of machinery required for efficient electron transport and cellular energy production. Approximately 1,200 genes, encoded from both nuclear and mitochondrial genomes, are essential for mitochondrial function. Studies suggest that mitochondrial and nuclear genomes co-evolve, and the coordinated expression of these interacting gene products are essential for optimal organism function. Incompatibilities between mtDNA and nuclear-encoded mitochondrial genes results in inefficiency in electron flow down the respiratory chain, differential oxidative phosphorylation efficiency, increased release of free radicals, altered intracellular Ca²⁺ signaling, and reduction of catalytic sites and ATP production. This review explores the role of mitonuclear incompatibility in BD susceptibility and resilience against environmental stressors.

The role of brain barriers in the neurokinetics and pharmacodynamics of lithium

Lithium (Li) is the most widely used mood stabilizer in treating patients with bipolar disorder. However, more than half of the patients do not or partially respond to Li therapy, despite serum Li concentrations in the serum therapeutic range. The exact mechanisms underlying the pharmacokinetic-pharmacodynamic (PK-PD) relationships of lithium are still poorly understood and alteration in the brain pharmacokinetics of lithium may be one of the mechanisms explaining the variability in the clinical response to Li. Brain barriers such as the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) play a crucial role in controlling blood-to-brain and brain-to-blood exchanges of various molecules including central nervous system (CNS) drugs. Recent in vivo studies by nuclear resonance spectroscopy revealed heterogenous brain distribution of Li in human that were not always correlated with serum concentrations, suggesting regional and variable transport mechanisms of Li through the brain barriers. Moreover, alteration in the functionality and integrity of brain barriers is reported in various CNS diseases, as a cause or a consequence and in this regard, Li by itself is known to modulate BBB properties such as the expression and activity of various transporters, metabolizing enzymes, and the specialized tight junction proteins on BBB. In this review, we will focus on recent knowledge into the role of the brain barriers as key-element in the Li neuropharmacokinetics which might improve the understanding of PK-PD of Li and its interindividual variability in drug response.

Mesocortical BDNF signaling mediates antidepressive-like effects of lithium

Lithium has been used to treat major depressive disorder, yet the neural circuit mechanisms underlying this therapeutic effect remain unknown. Here, we demonstrated that the ventral tegmental area (VTA) dopamine (DA) neurons that project to the medial prefrontal cortex (mPFC), but not to nucleus accumbens (NAc), contributed to the antidepressive-like effects of lithium. Projection-specific electrophysiological recordings revealed that high concentrations of lithium increased firing rates in mPFC-, but not NAc-, projecting VTA DA neurons in mice treated with chronic unpredictable mild stress (CMS). In parallel, chronic administration of high-dose lithium in CMS mice restored the firing properties of mPFC-projecting DA neurons, and also rescued CMS-induced depressive-like behaviors. Nevertheless, chronic lithium treatment was insufficient to change the basal firing rates in NAc-projecting VTA DA neurons. Furthermore, chemogenetic activation of mPFC-, but not NAc-, projecting VTA DA neurons mimicked the antidepressive-like effects of lithium in CMS mice. Chemogenetic downregulation of VTA-mPFC DA neurons' firing activity abolished the antidepressive-like effects of lithium in CMS mice. Finally, we found that the antidepressant-like effects induced by high-dose lithium were mediated by BNDF signaling in the mesocortical DA circuit. Together, these results demonstrated the role of mesocortical DA projection in antidepressive-like effects of lithium and established a circuit foundation for lithium-based antidepressive treatment.

Neurobiology of early psychosis

Background

Neurobiological studies of the early course of psychoses, such as schizophrenia, allow investigation of pathophysiology without the confounds of illness chronicity and treatment.

Aims

To review the recent literature on the biology of the early course of psychoses.

Method

We carried out a critical appraisal of the recent findings in the neurobiology of early psychoses, using structural, functional and neurochemical imaging techniques.

Results

Brain structural alterations are present early in the illness and may predate symptom onset. Some changes, notably those in frontal and temporal lobes, can progress during the early phases of the illness. Functional and neurochemical brain abnormalities can also be seen in the premorbid and the early phases of the illness. Some, although not all, changes can be trait-like whereas some others might progress during the early years.

Conclusions

A better understanding of such changes, especially during the critical periods of the prodrome, around the transition to the psychotic phase and during the early phases of the illness is crucial for continued research into preventive intervention strategies.

Protective effect of lithium chloride against hypoglycemia-induced apoptosis in neuronal PC12 cell

Hypoglycemia is defined by an arbitrary plasma glucose level lower than 3.9mmol/L and is a most common and feared adverse effect of treatment of diabetes mellitus. Emerging evidences demonstrated that hypoglycemia could induce enhanced apoptosis. Lithium chloride (LiCl), a FDA approved drug clinically used for treatment of bipolar disorders, is recently proven having neuroprotection against various stresses in the cellular and animal models of neural disorders. Here, we have established a hypoglycemia model in vitro and assessed the neuroprotective efficacy of LiCl against hypoglycemia-induced apoptosis and the underlying cellular and molecular mechanisms. Our studies showed that LiCl protects against hypoglycemia-induced neurotoxicity in vitro. Exposure to hypoglycemia results in enhanced apoptosis and the underlying cellular and molecular mechanisms involved inhibition of the canonical Wnt signaling pathway by decreasing wnt3a levels, β-catenin levels and increasing GSK-3β levels, which was confirmed by the use of Wnt-specific activator LiCl. Hypoglycemia-induced apoptosis were significantly reversed by LiCl, leading to increased cell survival. LiCl also alters the expression/levels of the Wnt pathway genes/proteins, which were reduced due to exposed to hypoglycemia. Overall, our results conclude that LiCl provides neuroprotection against hypoglycemia-induced apoptosis via activation of the canonical Wnt signaling pathway.

Differential effects of endogenous lithium on neurobehavioural functioning: a study on auditory evoked potentials

Lithium occurs naturally in food and water. Low environmental concentrations in drinking water are associated with mental illnesses and behavioural offences, and at therapeutic dosages it is used to treat psychiatric (especially affective) disorders, partly by facilitating serotonergic (5-HT) neurotransmission. As little is known about the psychophysiological role of nutritional lithium in the general population, endogenous lithium concentrations were hypothesised to be associated with measurable effects on emotional liability and the loudness dependence (LD) that is proposed as one of the most valid indicators of 5-HT neurotransmission. Auditory evoked potentials of healthy volunteers [N=36] with high (>2.5 microg/l) or low (<1.5 microg/l) lithium serum concentrations were recorded. Emotional liability was assessed using the Brief Symptom Inventory (BSI). Low-lithium levels correlated with Somatisation while correlations between lithium and LD were not significant. Still, LD correlated positively with Paranoid Ideation, negatively with Anxiety and, in the high-lithium group, inversely with further aspects of emotional liability (Depression, Psychological Distress). In conclusion, the effects of low levels of endogenous lithium are associated with emotional liability, and high levels with some protective effects, although findings remain inconclusive regarding LD. Potential benefits of endogenous lithium on neurobehavioural functioning, especially in high-risk individuals, would have public health implications.

A three-month, open-label, single-arm trial evaluating the safety and pharmacokinetics of oral lithium in patients with chronic spinal cord injury

OBJECTIVES

Lithium has recently been found to enhance neuronal regeneration and differentiation. This arouses its potential use to treat spinal cord injury patients. The safety and pharmacokinetics of lithium are not verified for this group of patients as their internal organ functions may change. This is a phase 1 clinical trial to evaluate the safety and pharmacokinetics of lithium in spinal cord injury patients.

METHODS

A total of 20 chronic spinal cord injury subjects were recruited. Oral lithium carbonate was given in divided dose to maintain the serum lithium level 0.6-1.2 mmol l(-1) for 6 weeks. Safety parameters, adverse events and pharmacokinetic data were carefully collected and monitored.

RESULTS

No severe adverse event was documented. All blood parameters remained stable. Nausea and vomiting were the most common complaints but tolerance was improved in 2 weeks for most subjects. A wide range of oral doses was required to maintain serum lithium level at the targeted range. However, the dose for individual subject was relatively constant.

CONCLUSION

This phase 1 clinical trial is the first report indicating the safety of lithium in chronic spinal cord injury patients. It is well tolerated after the first 2 weeks. Individual titration of lithium is essential to maintain an optimal serum lithium level but once the desirable level is achieved, the oral dose remains relatively unchanged for maintenance.

Lithium: a novel treatment for Alzheimer's disease?

Lithium is an alkali metal. First described as a mood stabilizer in 1949, it remains an efficacious treatment for bipolar disorders. Recent emerging evidence of its neuroprotective and neurogenic effects alludes to lithium's potential therapeutic use in stroke and neurodegenerative diseases. One intriguing clinical application is in the treatment of Alzheimer's disease. Ongoing clinical trials are evaluating lithium's abilities to lower tau and beta-amyloid levels in cerebrospinal fluid in Alzheimer's patients. This review summarizes the supporting evidence and safety profiles of lithium's use in the treatment of neurological diseases, especially Alzheimer's disease.

Management of Lithium Toxicity

Lithium salts have been used in the prophylaxis and treatment of depression and bipolar disorder for >50 years. Lithium has a narrow therapeutic range, and several well characterised adverse effects limit the potential usefulness of higher doses. Acute ingestion in lithium-naive patients is generally associated with only short-lived exposure to high concentrations, due to extensive distribution of lithium throughout the total body water compartment. Conversely, chronic toxicity and acute-on-therapeutic ingestion are associated with prolonged exposure to higher tissue concentrations and, therefore, greater toxicity. Lithium toxicity may be life threatening, or result in persistent cognitive and neurological impairment. Therefore, enhanced lithium clearance has been explored as a means of minimising exposure to high tissue concentrations. Although haemodialysis is highly effective in removing circulating lithium, serum concentrations often rebound so repeated or prolonged treatment may be required. Continuous arteriovenous haemodiafiltration and continuous venovenous haemodiafiltration increase lithium clearance, albeit to a lesser extent than haemodialysis, and are more widely accessible. Haemodiafiltration sustained for >16 hours allows effective removal of total body lithium, thereby avoiding rebound effects. Enhanced elimination should be considered in patients at greatest risk of severe poisoning: namely those with chronic or acute-on-therapeutic toxicity, those with clinically significant features, and those with chronic toxicity whose serum lithium concentration is >2.5 mmol/L. The choice between haemodialysis and continuous haemodiafiltration techniques will depend on local accessibility and urgency of enhancing lithium elimination. Further research is required to establish the potential benefits of assisted elimination on clinical outcome in patients with lithium poisoning.

Neurochemical predictors of response to pharmacologic treatments for bipolar disorder

Bipolar disorder is a common psychiatric disorder that is characterized by recurrent episodes of mania and often depression. Mood stabilizers and antipsychotics are first-line pharmacologic options for patients with bipolar disorder. However, the exact mechanisms by which these medications exert the mood stabilizing effects are unknown. Additionally, individuals with bipolar disorder often try several medications unsuccessfully before achieving mood stabilization. Magnetic resonance spectroscopy (MRS) is a noninvasive neuroimaging technique that can be used to identify the neurochemical effects and predictors of response to medications commonly used to treat bipolar disorder. MRS may facilitate targeted treatment interventions and decrease the morbidity and mortality associated with this illness. Examining the mechanisms of action of pharmacologic agents used to treat bipolar disorder may clarify the neurophysiologic basis of bipolar disorder. We will review recent MRS investigations that have evaluated the neurochemical effects of pharmacologic treatments and predictors of treatment response in patients with bipolar disorder.

Chronic lithium treatment attenuates intracellular calcium mobilization

Elevated basal intracellular calcium (Ca(2+)) levels ([Ca(2+)](B)) in B lymphoblast cell lines (BLCLs) from bipolar I disorder (BD-I) patients implicate altered Ca(2+) homeostasis in this illness. Chronic lithium treatment affects key proteins modulating intracellular Ca(2+) signaling. Thus, we sought to determine if chronic exposure to therapeutic lithium concentrations also modifies intracellular Ca(2+) homeostasis in this surrogate cellular model of signal transduction disturbances in BD. BLCLs from BD-I (N=26) and healthy subjects (N=17) were regrown from frozen stock and incubated with 0.75 mM lithium or vehicle for 24 h (acute) or 7 days (chronic). [Ca(2+)](B), lysophosphatidic acid (LPA)-stimulated Ca(2+) mobilization ([Ca(2+)](S)), and thapsigargin-induced store-operated Ca(2+) entry (SOCE) were determined using ratiometric fluorometry with Fura-2. Compared with vehicle, chronic lithium exposure resulted in significantly higher [Ca(2+)](B) (F=8.47; p=0.006) in BLCLs from BD-I and healthy subjects. However, peak LPA-stimulated [Ca(2+)](S) and SOCE were significantly reduced (F=11.1, p=0.002 and F=8.36, p=0.007, respectively). Acute lithium exposure did not significantly affect measured parameters. In summary, the effect of chronic lithium to elevate [Ca(2+)](B) in BLCLs while attenuating both receptor-stimulated and SOCE components of intracellular Ca(2+) mobilization in BLCLs suggests that modulation of intracellular Ca(2+) homeostasis may be important to the therapeutic action of lithium.

Biological predictors of lithium response in bipolar disorder

In order to prescribe lithium appropriately to patients with bipolar disorder, predictors of lithium response are helpful. The present paper reviews the biological predictors of lithium response. As a positive predictor of lithium response, the following have been reported: strong loudness dependence of the auditory-evoked N1/P2-response; higher brain lithium concentration; lower inositol monophosphatase (IMPase) mRNA expression; higher serotonin-induced calcium mobilization; increased N-acetyl-aspartate peak and decreased myo-inositol peak; white matter hyperintensity; decreased intracellular pH; higher frequency of phospholipase C gamma-1 (PLCG1)-5 repeat and PLCG1-8 repeat; and C973A polymorphism in the inositol polyphosphate 1-phosphatase gene. In contrast the following have been reported as a predictor of negative lithium response: epileptiform abnormality of electroencephalography; human leukocyte antigen type A3; decreased phosphocreatine peak area after photic stimulation; and homozygotes for the short variant of the serotonin transporter gene. Most of the possible biological predictors of better lithium response, such as lower IMPase mRNA levels, white matter hyperintensity, lower brain intracellular pH, enhanced calcium response, and PLCG1-5 repeat had been detected as risk factors for bipolar disorder, suggesting that bipolar disorder responding well to maintenance lithium treatment is a distinct category having a certain neurobiological basis, although these findings need further replication. The search for biological predictors of lithium response is still in its infancy. Most of the laboratory or neuroimaging techniques used in these studies are not easily performed in clinical settings, so the development of an easy and useful laboratory test is needed.

Lithium in bipolar disorder: can drug concentrations predict therapeutic effect?

The evidence is reviewed for effective serum lithium concentrations for the acute and prophylactic treatment of mania and depression in patients with bipolar disorder. The efficacy of lithium in the treatment of acute manic episodes has been recognised for several decades, primarily using concentrations in the range of 0.8 to 2 mmol/L. The number of patients responding increases as the serum lithium concentration increases, although individual patients may respond at lower concentrations (<0.8 mmol/L). Lithium doses and serum concentrations similar to those used to treat acute mania have been studied in bipolar depression, with no evaluation of a relationship between concentration and clinical response. Several prospective controlled trials have evaluated this relationship in the prophylactic treatment of bipolar disorder. Maintaining higher serum lithium concentrations (0.8 to 1 mmol/L) improves the likelihood of good effect in prophylactic treatment, although individual patients may do well on lower concentrations. Despite the paucity of evidence to specifically support the efficacy of lithium at lower serum lithium concentrations in the elderly, lower target ranges (0.5 to 0.8 mmol/L) are commonly recommended due to an increased sensitivity to adverse effects, particularly neurotoxicity. The serum lithium concentrations recommended in adults have been applied to children; however, this has not been studied. Overall, the evidence suggests a relationship between serum lithium concentration and therapeutic effect, although the exact nature of this relationship is not clear. For example, it is not known why some people respond to lower concentrations and others do not. There are many factors that influence studies trying to elucidate this relationship. Many of these factors are related to the interpretation of the serum lithium concentration. In summary, patients have an increased chance of responding to lithium if 12-hour serum lithium concentrations at steady state are above 0.8 mmol/L. Many patients will respond to lower concentrations (0.4 to 0.7 mmol/L), but we are unable to identify these patients a priori. The relationship between serum lithium concentrations and adverse effects is also very important in determining appropriate target lithium concentrations. The current best advice is to individualise the target serum lithium concentrations based on efficacy and tolerability and to optimise the interpretation of these concentrations by ensuring within-patient consistency with respect to dosage schedule, lithium preparation and the timing of blood sampling.

Lithium-related genetics of bipolar disorder

Lithium is a potent prophylactic medication and mood stabilizer in bipolar disorder. However, clinical outcome is variable, and its therapeutic effect manifests after a period of chronic treatment, implying a progressive and complex biological response process. Signal transduction systems known to be perturbed by lithium involve phosphoinositide (PI) turnover, activation of the Wnt pathway via inhibition of glycogen synthase kinase-3beta (GSK-3beta), and a growth factor-induced, Akt-mediated signalling that promotes cell survival. These pathways, acting in synergy, probably prompt the amplification of lithium signal causing such immense impact on the neuronal network. The sequencing of the human genome presents an unparallelled opportunity to uncover the full molecular repertoire involved in lithium action. Interrogation of high-resolution expression microarrays and protein profiles represents a strategy that should help accomplish this goal. A recent microarray analysis on lithium-treated versus untreated PC12 cells identified multiple differentially altered transcripts. Lithium-perturbed genes, particularly those that map to susceptibility regions, could be candidate risk-conferring factors for mood disorders. Transcript and protein profiling in patients could reveal a lithium fingerprint for responsiveness or nonresponsiveness, and a signature motif that may be diagnostic of a specific phenotype. Similarly, lithium-sensitive gene products could provide a new generation of pharmacological targets.

Brain lithium concentrations in bipolar disorder patients: preliminary (7)Li magnetic resonance studies at 3 T

BACKGROUND

This study was conducted to investigate the feasibility of human brain (7)Li MRS investigations at a high magnetic field (3 T), and to further explore the relationship between brain and serum lithium measures in lithium-treated bipolar patients.

METHODS

Eight bipolar disorder type I patients (5 males, 3 females; mean age +/- SD = 33 +/- 9 years) were studied. A 3-T scanner, using a dual-tuned ((1)H and (7)Li) echoplanar imaging (EPI) compatible radiofrequency (RF) birdcage coil was used. (7)Li magnetic resonance spectroscopy (MRS) signal was acquired at the frequency of 49.64 MHz using an imaging selective in vivo spectroscopy (ISIS) sequence (TR = 15 sec, 128 averages), and quantitation was obtained in reference to an external standard.

RESULTS

The mean +/- SD oral lithium dose was 1265 +/- 442 mg/day, and the mean +/- SD 12-hour serum level was 0.69 +/- 0.19 mEq/L. The measured brain lithium concentrations varied from 0.23 to 0.55 mEq/L (mean +/- SD = 0.35 +/- 0.11 mEq/L). The brain-serum ratios varied from 0.30 to 0.80 (mean +/- SD = 0.52 +/- 0.16). Subjects on single daily doses of lithium at bedtime (n = 5) had higher brain-serum lithium ratios compared with those on twice-a-day schedules (n = 3) (0.61 +/- 0.12 and 0.37 +/- 0.07, respectively; Mann--Whitney U test, Z = -2.24, p =.03).

CONCLUSIONS

This study demonstrated for the first time the feasibility of (7)Li MRS human studies at 3 T. Future studies should examine a possible role for this methodology in investigations of lithium refractoriness and prediction of treatment outcome in bipolar patients.

Brain lithium measurements with (7)Li magnetic resonance spectroscopy (MRS): a literature review

7Li magnetic resonance spectroscopy (MRS) has been successfully used in recent years as a new tool to measure brain tissue lithium concentrations in vivo. After demonstration of its feasibility in animal studies over a decade ago, human investigations have characterized the brain pharmacokinetics of lithium. Preliminary studies have investigated brain pharmacokinetic correlates of clinical response in the treatment of bipolar disorder patients, with indication of possible clinical relevance of 7Li MRS measures. In this paper we reviewed the accumulated literature in this area, and discuss possible directions for this research in the context of preliminary studies conducted by our group that demonstrated the feasibility of 7Li MRS at 3 T.

Applications of (7)Li NMR in biomedicine

The applications of (7)Li NMR spectroscopy and imaging in biology and experimental medicine have been progressing steadily. The interest derives primarily from the clinical use of Li salts to treat mania and manic-depressive illness. One area of investigation is ionic transport across the cellular membrane and compartmentation, so as to elucidate the mechanism(s) of therapeutic action and toxicity in clinical practice. The second is the development of a noninvasive, in vivo analytical tool to measure brain Li concentrations in humans, both as an adjunct to treatment and as a mechanistic probe. Here we review progress to date in this area.

Metabolism and excretion of mood stabilizers and new anticonvulsants

1. The mood stabilizers lithium, carbamazepine (CBZ), and valproate (VPA), have differing pharmacokinetics, structures, mechanisms of action, efficacy spectra, and adverse effects. Lithium has a low therapeutic index and is renally excreted and hence has renally-mediated but not hepatically-mediated drug-drug interactions. 2. CBZ has multiple problematic drug-drug interactions due to its low therapeutic index, metabolism primarily by a single isoform (CYP3A3/4), active epoxide metabolite, susceptibility to CYP3A3/4 or epoxide hydrolase inhibitors, and ability to induce drug metabolism (via both cytochrome P450 oxidation and conjugation). In contrast, VPA has less prominent neurotoxicity and three principal metabolic pathways, rendering it less susceptible to toxicity due to inhibition of its metabolism. However, VPA can increase plasma concentrations of some drugs by inhibiting metabolism and increase free fractions of certain medications by displacing them from plasma proteins. 3. Older anticonvulsants such as phenobarbital and phenytoin induce hepatic metabolism, may produce toxicity due to inhibition of their metabolism, and have not gained general acceptance in the treatment of primary psychiatric disorders. 4. The newer anticonvulsants felbamate, lamotrigine, topiramate, and tiagabine have different hepatically-mediated drug-drug interactions, while the renally excreted gabapentin lacks hepatic drug-drug interactions but may have reduced bioavailability at higher doses. 5. Investigational anticonvulsants such as oxcarbazepine, vigabatrin, and zonisamide appear to have improved pharmacokinetic profiles compared to older agents. 6. Thus, several of the newer anticonvulsants lack the problematic drug-drug interactions seen with older agents, and some may even (based on their mechanisms of action and preliminary preclinical and clinical data) ultimately prove to have novel psychotropic effects.

Duration of lithium treatment and brain lithium concentration in patients with unipolar and schizoaffective disorder--a study with magnetic resonance spectroscopy

Twenty psychiatric patients on lithium medication were examined with 7-Li-magnetic resonance spectroscopy of the brain. Patients on long-term lithium treatment (> 6 months) were compared with a short-term group who had been taking lithium for between 4 and 8 weeks. Patients met DSM-III-R criteria for either recurrent unipolar depressive disorder (DSM-III-R 296.3x) or schizoaffective disorder, depressive type (DSM-III-R 295.70). The brain:serum lithium ratio was 0.76 +/- 0.26; there was no significant difference between short-term and long-term treatment. In the group of long-term treatment patients there was a positive correlation between lithium dose per day and brain lithium concentration (R = .72, p < .01), and between lithium plasma concentration and brain lithium concentration (R = .65, p < .05). In the short-term group, however, there was no significant correlation for these parameters. No differences between unipolar and schizoaffective disorder were found.

Lithium and neuroleptics in combination: is there enhancement of neurotoxicity leading to permanent sequelae?

Neurotoxicity in relation to concomitant administration of lithium and neuroleptic drugs, particularly haloperidol, has been an ongoing issue. This study examined whether use of lithium with neuroleptic drugs enhances neurotoxicity leading to permanent sequelae. The Spontaneous Reporting System database of the United States Food and Drug Administration and extant literature were reviewed for spectrum cases of lithium/neuroleptic neurotoxicity. Groups taking lithium alone (Li), lithium/haloperidol (LiHal) and lithium/ nonhaloperidol neuroleptics (LiNeuro), each paired for recovery and sequelae, were established for 237 cases. Statistical analyses included pairwise comparisons of lithium levels using the Wilcoxon Rank Sum procedure and logistic regression to analyze the relationship between independent variables and development of sequelae. The Li and Li-Neuro groups showed significant statistical differences in median lithium levels between recovery and sequelae pairs, whereas the LiHal pair did not differ significantly. Lithium level was associated with sequelae development overall and within the Li and LiNeuro groups; no such association was evident in the LiHal group. On multivariable logistic regression analysis, lithium level and taking lithium/haloperidol were significant factors in the development of sequelae, with multiple possibly confounding factors (e.g., age, sex) not statistically significant. Multivariable logistic regression analyses with neuroleptic dose as five discrete dose ranges or actual dose did not show an association between development of sequelae and dose. Database limitations notwithstanding, the lack of apparent impact of serum lithium level on the development of sequelae in patients treated with haloperidol contrasts notably with results in the Li and LiNeuro groups. These findings may suggest a possible effect of pharmacodynamic factors in lithium/neuroleptic combination therapy.

Twelve-hour brain lithium concentration in lithium maintenance treatment of manic-depressive disorder: daily versus alternate-day dosing schedule

The 12-h brain lithium concentration was measured by lithium-7 magnetic resonance spectroscopy in ten manic-depressive patients receiving daily or alternate-day lithium carbonate treatment. The median dose of lithium carbonate was 800 mg in the daily treatment group and 1200 mg in the alternate-day group. Median 12-h serum lithium concentration in the two groups was 0.86 mmol l-1 and 0.55 mmol l-1, respectively, while the corresponding concentration in brain was 0.67 mmol l-1 and 0.52 mmol l-1, respectively. The 12-h brain lithium concentration was independent of lithium dosing schedule (multiple linear regression), but correlated significantly with the 12-h serum lithium concentration (P = 0.003; B = 0.53, 95% c.l. 0.24-0.82; beta = 0.83). Thus at identical 12-h serum lithium concentrations the 12-h brain lithium concentration is similar with both treatment regimes. As the risk of manic-depressive relapse during alternate-day lithium treatment is in our experience 3-fold greater than with daily treatment (at similar mean 12-h serum lithium concentration), the findings suggest that the difference in the prophylactic efficacy of the two dosing schedules is unrelated to differences in the 12-h brain lithium concentration.

Functional Brain Imaging, Limbic Function, and Affective Disorders

For more than a century, mesial cerebral structures have been candidate substrates for the mediation of emotional experience. Although limbic structures were originally conceived as forming a midline ring, emerging evidence suggests that emotional processes may be related more closely to anterior paralimbic (anterior limbic and nearby cortical) regions than to posterior limbic regions. In addition, basal ganglia-thalamocortical circuits for various cerebral processes have been proposed, including one involving anterior paralimbic structures thought to mediate emotion. Recent brain imaging studies have advanced this thesis by demonstrating anterior paralimbic activation during affective arousal in healthy volunteers. The overwhelming majority of functional imaging studies of both primary and secondary depression has demonstrated decreased anterior paralimbic and prefrontal cortical activity, the latter of which often correlated with severity of depression and resolved with symptom remission. A few studies have noted increased activity in these same regions, which may reflect heterogeneity due to particular illness subtypes. Preliminary evidence has suggested that baseline functional abnormalities in these structures may relate to diagnostic subtypes and provide differential markers of therapeutic responses. New imaging methods with greater sensitivity, spatial and temporal resolution, and biochemical specificity promise to fuel further insights into the neurobiology of normal emotion in health, subtypes of affective disorders, and perhaps even improved targeting of therapeutic interventions.

Lithium side effects in relation to brain lithium concentration measured by lithium-7 magnetic resonance spectroscopy

1. The relationship between lithium (Li) side effects and brain Li concentration was examined in 17 patients with bipolar disorder treated with Li and other psychotropic drugs. 2. Brain Li concentration was measured by Li-7 magnetic resonance spectroscopy (MRS). Side effects were assessed using the UCLA General Side Effect Rating Scale For Lithium Treatment (GSE). 3. There was no correlation between the total GSE score and the brain, serum, or erythrocyte Li concentrations. Patients with hand tremor had significantly higher brain Li level (0.51 + or - 0.27 mM) than those without apparent tremor (0.36 + or - 0.20 mM), but no significant difference in serum Li level was seen. As far as the patients had hand tremor, they rarely had brain Li concentration less than the therapeutic range (1 of 15 measurement). On the other hand, they often had brain Li levels less than the therapeutic range when they did not have apparent tremor (13 of 52 measurements). 4. This preliminary study suggests that hand tremor is associated with the brain Li concentration.

Monitoring of lithium levels in human serum after therapy with lithium preparations by capillary isotachophoresis

An isotachophoretic method for the evaluation of the level of lithium salts in serum samples was optimized. Use of operating systems containing polyethylene glycol permitted the separation of cationically migrating components from Li (i.e., Na, K and Ca). The pretreatment of serum samples involves only appropriate dilution with demineralized water depending on the concentration of the major components such as sodium. The lithium levels were studied both in model samples and serum from patients treated with lithium preparations.

Variability of brain lithium levels during maintenance treatment: a magnetic resonance spectroscopy study

In vivo magnetic resonance spectroscopy (MRS) was used to determine the relationship between serum and brain lithium levels in bipolar patients (n=25). Over the broad range of serum lithium levels observed, the correlation (r=.68) with brain lithium levels was high. This correlation was much weaker (r=.39) when limited to only those patients with serum lithium levels in the range of 0.6-1.0 mmol/l. This variability may account for failure of lithium prophylaxis in some patients who have serum lithium levels in the therapeutic range.

Comparison of lithium ratio between African-American and Caucasian bipolar patients

Lithium RBC/plasma ratio (LR) was studied in 34 bipolar subjects on therapeutic doses of lithium carbonate. The sample was divided into 22 Caucasians and 12 African-Americans to observe possible ethnic differences in LR as previously reported. The latter group demonstrated a higher LR as well as increased reports of side effects (p < .05), even after controlling previous confounding factors. Our findings suggest that African-Americans may be more susceptible to the side effects associated with lithium treatment, and consequently, lower dosages may be necessary for this group.

24-hour lithium concentration in human brain studied by Li-7 magnetic resonance spectroscopy

Brain and serum lithium concentrations were measured every second hour during a 24-hr period following lithium intake, and again 48-hr later in two normal subjects in steady state lithium treatment receiving lithium carbonate (Priadel Synthelabo) once every evening. The brain-lithium concentration was measured by 7Li magnetic resonance spectroscopy (MRS). The brain lithium level was found to undulate in a peak-trough pattern that followed the serum lithium profile, although in an attenuated form. The brain/serum lithium concentration ratio varied considerably during the 48-hr period, ranging from 0.5 to 1.3, but the ratio was independent of the serum-lithium concentration. The median half-life for lithium was 28 hr in the brain, and 16 hr in serum. The brain lithium concentration in the morning was about 75% of the clinically relevant standard 12-hr serum lithium concentration. The finding that brain lithium undulates during the day means that MRS measurements of brain lithium can only be compared if carried out under standard conditions that include a fixed interval following lithium intake and an identical treatment regimen.