Drug-drug interactions as a determinant of elevated lithium serum levels in daily clinical practice

Lithium surveillance by community pharmacists and physicians in ambulatory patients: a retrospective cohort study

BACKGROUND

Shared care agreements between clinical pharmacists and physicians can improve suboptimal lithium monitoring in in- and outpatient settings. However, it is unknown whether incorporating community pharmacists in such agreements can also improve lithium monitoring in an outpatient setting.

AIM

To assess the necessity for a shared care agreement for lithium monitoring in our region by investigating: intervention rates by community pharmacists and whether those are sufficient; lithium monitoring by physicians in ambulatory patients; the extent of laboratory parameter exchange to community pharmacists.

METHOD

Patient files of lithium users were surveyed in a retrospective cohort study among 21 community pharmacies in the Northern Netherlands. Outcome was the intervention rate by community pharmacists and whether those were deemed sufficient by an expert panel. Additionally, we investigated both the percentages of patients monitored according to current guidelines and of laboratory parameters exchanged to community pharmacists.

RESULTS

129 patients were included. Interventions were performed in 64.4% (n = 29), 20.8% (n = 5), and 25.0% (n = 1) of initiations, discontinuations, and dosage alterations of drugs interacting with lithium, respectively. The expert panel deemed 40.0% (n = 14) of these interventions as "insufficient". Physicians monitored 40.3% (n = 52) of the patients according to current guidelines for lithium serum levels and kidney functions combined. Approximately half of the requested laboratory parameters were available to the community pharmacist.

CONCLUSION

Intervention rates by community pharmacists and lithium monitoring by physicians can be improved. Therefore, a shared care agreement between community pharmacists, clinical pharmacists, and physicians is needed to improve lithium monitoring in ambulatory patients.

Therapeutic Drug Monitoring of Antidepressants: An Underused but Potentially Valuable Tool in Primary Care

Depressive disorders are among the most burdensome diseases globally in terms of prevalence, as well as in terms of quality of life, morbidity, and mortality. Hence, it is becoming increasingly common for primary care physicians to administer and monitor the treatment of individuals affected by depressive disorders. In this framework, Therapeutic Drug Monitoring (TDM) comes to the forefront. TDM is the measurement of specific drugs in the blood or plasma/serum, and its usefulness lies in the fact that it allows physicians to assess drug levels to personalize and optimize treatments. TDM has been used for decades to measure several classes of psychotropic drugs, such as antiepileptics and antipsychotics, but the use of this tool is still in its infancy in regard to antidepressants. In the context of primary care, TDM of antidepressant drug treatment shows promise, as it can enable primary care physicians to monitor the safety and efficacy of the treatment, leaving to secondary care, i.e., psychiatrists, the management of the more complex clinical cases.

Deep Vein Thrombosis after Lithium Toxicity: A Report of Two Cases and Literature Review

Lithium administration can reportedly cause toxicity, including lithium-associated thrombosis; however, not all reported cases of this adverse effect have been attributable to lithium overdoses. We report here two cases of deep vein thrombosis that occurred in association with lithium toxicity. Lithium overdose was deemed to be the cause in only one of these cases; a patient in whom deep vein thrombosis occurred 11 days after identification of lithium toxicity. In the other patient, the deep vein thrombosis occurred 15 days after diagnosis of lithium toxicity; this patient was not considered to have been overdosed. Both patients had other risk factors in addition to receiving lithium. We recommend monitoring D-dimer concentrations to facilitate early detection of deep vein thrombosis in patients with lithium toxicity.

The importance of monitoring renal function and concomitant medication to avoid toxicity in patients taking lithium

Lithium, which is used for bipolar disorder, can cause toxicity. There are two categories of lithium toxicity, namely, overdose-related and not overdose-related. However, the treatment and prognosis of each type of toxicity are not clearly understood. We, therefore, compared the clinical characteristics of patients with overdose-related and not overdose-related lithium toxicity. Relevant data were obtained from the medical records of 16 patients with lithium toxicity, and renal function and concomitant medications were retrospectively compared between the two groups. We also compared the treatment for, manifestations of, and duration of hospitalization between the two types of lithium toxicity. The not overdose-related group more frequently had a low creatinine clearance (<50 mL/min) than did the overdose-related group (P = 0.01). Multivariable regression analysis demonstrated that creatinine clearance <50 mL/min was a significant predictor of lithium toxicity in the not overdose-related group (P = 0.01). Tremor and dysarthria occurred only in the not overdose-related group, and duration of hospitalization was significantly longer in the not overdose-related than overdose-related group (P = 0.01). Clinicians must monitor the renal function of patients taking lithium, even when in compliance with the prescribed dosage, because they are at long-term risk of lithium toxicity.

Pharmacological Augmentation in Unipolar Depression: A Guide to the Guidelines

BACKGROUND

Pharmacological augmentation is a recommended strategy for patients with treatment-resistant depression. A range of guidelines provide advice on treatment selection, prescription, monitoring and discontinuation, but variation in the content and quality of guidelines may limit the provision of objective, evidence-based care. This is of importance given the side effect burden and poorer long-term outcomes associated with polypharmacy and treatment-resistant depression. This review provides a definitive overview of pharmacological augmentation recommendations by assessing the quality of guidelines for depression and comparing the recommendations made.

METHODS

A systematic literature search identified current treatment guidelines for depression published in English. Guidelines were quality assessed using the Appraisal of Guidelines for Research and Evaluation II tool. Data relating to the prescription of pharmacological augmenters were extracted from those developed with sufficient rigor, and the included recommendations compared.

RESULTS

Total of 1696 records were identified, 19 guidelines were assessed for quality, and 10 were included. Guidelines differed in their quality, the stage at which augmentation was recommended, the agents included, and the evidence base cited. Lithium and atypical antipsychotics were recommended by all 10, though the specific advice was not consistent. Of the 15 augmenters identified, no others were universally recommended.

CONCLUSIONS

This review provides a comprehensive overview of current pharmacological augmentation recommendations for major depression and will support clinicians in selecting appropriate treatment guidance. Although some variation can be accounted for by date of guideline publication, and limited evidence from clinical trials, there is a clear need for greater consistency across guidelines to ensure patients receive consistent evidence-based care.

Drug-Drug Interactions Between Lithium and Cardiovascular as Well as Anti-Inflammatory Drugs

INTRODUCTION

Lithium is the gold standard in treating bipolar affective disorders. As patients become increasingly older, drug-drug interactions leading to decreased excretion of lithium represent a key issue in lithium safety. As no study considered the effect of comedications on lithium serum concentration in combination, we aimed to quantify the impact of drugs affecting renal blood flow and function and thus potentially interacting drugs (diuretics, ACE inhibitors, AT1 antagonists, and non-steroidal anti-inflammatory drugs) on lithium serum levels in addition to age, sex, and sodium and potassium serum levels as well as renal function.

METHODS

Retrospective data of lithium serum levels were analyzed in 501 psychiatric inpatients (2008-2015) by means of linear regression modelling.

RESULTS

The number of potentially interacting drugs was significantly associated with increasing serum levels of lithium in addition to the established factors of age, renal function, and sodium concentration. Additionally, absolute lithium levels were dependent on sex, with higher values in females. However, only NSAIDs were identified to increase lithium levels independently.

DISCUSSION

Routine clinical practice needs to focus on drugs affecting renal blood flow and function, especially on NSAIDs as over-the-counter medication that may lead to an increase in lithium serum concentration. To prevent intoxications, clinicians should carefully monitor the comedications, and they should inform patients about possible intoxications due to NSAIDs.

Compliance with the guidelines for laboratory monitoring of patients treated with lithium: A retrospective follow-up study among ambulatory patients in the Netherlands

OBJECTIVES

Laboratory monitoring of patients using lithium is important to prevent harm and to increase effectiveness. The aim of this study is to determine compliance with the guidelines for laboratory monitoring of patients treated with lithium overall and within subgroups.

METHODS

Patients having at least one lithium dispensing for 6 months or longer between January 2010 and December 2015 were identified retrospectively using data from the Dutch PHARMO Database Network. Laboratory monitoring was defined as being compliant with the Dutch Multidisciplinary Clinical Guideline Bipolar Disorders when lithium serum levels, creatinine and thyroid-stimulating hormone (TSH) had been measured at least every 6 months during lithium use.

RESULTS

Data were analyzed from 1583 patients with a median duration of 7- to 6-months period of lithium use. Results indicated that patients had been monitored over 6-month period for lithium serum levels 65% of the time, for creatinine 73% of the time and for TSH 54% of the time. Just over one seventh (16%) of patients had been monitored in compliance with the guidelines for all three parameters during total follow-up. Especially males, patients aged below 65 years, patients receiving prescriptions solely from general practitioners, prevalent users of lithium, patients without interacting co-medication, and patients without other days with laboratory measurements had been monitored less frequently in compliance with the guidelines.

CONCLUSIONS

A considerable proportion of patients had not been monitored in accordance with the guidelines. Further research is needed to understand the reasons for noncompliance and to implement strategies with the ultimate goal of optimizing safety and effectiveness for patients treated with lithium.

The Combination of Lithium and ACE Inhibitors: Hazardous, Critical, Possible?

Lithium is a well established therapeutic agent in the treatment of uni- and bipolar affective disorders. Angiotensin-converting enzyme (ACE) inhibitors are the most frequently used class of drugs in the treatment of cardiovascular diseases. Combination therapy with both may be considered in clinical practice on occurrence of arterial hypertension after years of successful lithium therapy, yet an increased risk of lithium intoxication in combination with ACE inhibitors has been described and thus the combination has been warned against. We describe three cases in which enalapril, lisinopril or ramipril was combined with lithium. Either additional co-medication with hydrochlorothiazide or dehydration rather than co-medication with ACE inhibitors could be identified as necessary factors for lithium intoxication. These cases suggest that a combination of lithium with ACE inhibitors is possible when sufficient hydration is ensured and a combination with hydrochlorothiazide is avoided. Lithium concentration should be controlled on a regular level.

Monitoring of patients treated with lithium for bipolar disorder: an international survey

Background

Adequate monitoring of patients using lithium is needed for optimal dosing and for early identification of patients with (potential) ADEs. The objective was to internationally assess how health care professionals monitor patients treated with lithium for bipolar disorder.

Methods

Using networks of various professional organizations, an anonymous online survey was conducted among health care professionals prescribing lithium. Target lithium serum levels and frequency of monitoring was assessed together with monitoring of physical and laboratory parameters. Reasons to and not to monitor and use of guidelines and institutional protocols, and local monitoring systems were investigated.

Results

The survey was completed by 117 health care professionals incorporating responses from twenty-four countries. All prescribers reported to monitor lithium serum levels on a regular basis, with varying target ranges. Almost all (> 97%) monitored thyroid and renal function before start and during maintenance treatment. Reported monitoring of other laboratory and physical parameters was variable. The majority of respondents (74%) used guidelines or institutional protocols for monitoring. In general, the prescriber was responsible for monitoring, had to request every monitoring parameter separately and only a minority of patients was automatically invited.

Conclusions

Lithium serum levels, renal and thyroid function were monitored by (almost) all physicians. However, there was considerable variation in other monitoring parameters. Our results help to understand why prescribers of lithium monitor patients and what their main reasons are not to monitor patients using lithium.

Electronic supplementary material

The online version of this article (10.1186/s40345-018-0120-1) contains supplementary material, which is available to authorized users.

Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for mood disorders

OBJECTIVES

To provide guidance for the management of mood disorders, based on scientific evidence supplemented by expert clinical consensus and formulate recommendations to maximise clinical salience and utility.

METHODS

Articles and information sourced from search engines including PubMed and EMBASE, MEDLINE, PsycINFO and Google Scholar were supplemented by literature known to the mood disorders committee (MDC) (e.g., books, book chapters and government reports) and from published depression and bipolar disorder guidelines. Information was reviewed and discussed by members of the MDC and findings were then formulated into consensus-based recommendations and clinical guidance. The guidelines were subjected to rigorous successive consultation and external review involving: expert and clinical advisors, the public, key stakeholders, professional bodies and specialist groups with interest in mood disorders.

RESULTS

The Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for mood disorders (Mood Disorders CPG) provide up-to-date guidance and advice regarding the management of mood disorders that is informed by evidence and clinical experience. The Mood Disorders CPG is intended for clinical use by psychiatrists, psychologists, physicians and others with an interest in mental health care.

CONCLUSIONS

The Mood Disorder CPG is the first Clinical Practice Guideline to address both depressive and bipolar disorders. It provides up-to-date recommendations and guidance within an evidence-based framework, supplemented by expert clinical consensus.

MOOD DISORDERS COMMITTEE

Professor Gin Malhi (Chair), Professor Darryl Bassett, Professor Philip Boyce, Professor Richard Bryant, Professor Paul Fitzgerald, Dr Kristina Fritz, Professor Malcolm Hopwood, Dr Bill Lyndon, Professor Roger Mulder, Professor Greg Murray, Professor Richard Porter and Associate Professor Ajeet Singh.

INTERNATIONAL EXPERT ADVISORS

Professor Carlo Altamura, Dr Francesco Colom, Professor Mark George, Professor Guy Goodwin, Professor Roger McIntyre, Dr Roger Ng, Professor John O'Brien, Professor Harold Sackeim, Professor Jan Scott, Dr Nobuhiro Sugiyama, Professor Eduard Vieta, Professor Lakshmi Yatham.

AUSTRALIAN AND NEW ZEALAND EXPERT ADVISORS

Professor Marie-Paule Austin, Professor Michael Berk, Dr Yulisha Byrow, Professor Helen Christensen, Dr Nick De Felice, A/Professor Seetal Dodd, A/Professor Megan Galbally, Dr Josh Geffen, Professor Philip Hazell, A/Professor David Horgan, A/Professor Felice Jacka, Professor Gordon Johnson, Professor Anthony Jorm, Dr Jon-Paul Khoo, Professor Jayashri Kulkarni, Dr Cameron Lacey, Dr Noeline Latt, Professor Florence Levy, A/Professor Andrew Lewis, Professor Colleen Loo, Dr Thomas Mayze, Dr Linton Meagher, Professor Philip Mitchell, Professor Daniel O'Connor, Dr Nick O'Connor, Dr Tim Outhred, Dr Mark Rowe, Dr Narelle Shadbolt, Dr Martien Snellen, Professor John Tiller, Dr Bill Watkins, Dr Raymond Wu.

Long-term effect of lithium maintenance therapy on estimated glomerular filtration rate in patients with affective disorders: a population-based cohort study

BACKGROUND

For more than 40 years, the long-term effect of lithium maintenance therapy on renal function has been debated. We aimed to assess the effect of lithium maintenance therapy on estimated glomerular filtration rate (eFGR) in patients with affective disorders, and explore predictors for a decrease in eGFR.

METHODS

This population-based cohort study included adult patients (18-65 years of age at baseline) in Tayside (Scotland, UK) who had recently started on lithium maintenance treatment between Jan 1, 2000, and Dec 31, 2011 (retrospectively assigned to the lithium group) or those with exposure to other first-line drugs used in the treatment of affective disorders (quetiapine, olanzapine, and semisodium valproate) during the same period (retrospectively assigned to the comparator group). Patients had to have at least 6 months of (incidence) exposure to lithium or any of the comparator drugs, at least two eGFR values available in the observation period (one at baseline and at least one after ≥6 months post baseline). We excluded patients with previous exposure to lithium or one of the comparator drugs, those with a previous diagnosis of schizophrenia or other psychotic disorder, those with glomerular disease, tubulo-interstitial disease, or chronic kidney disease stages 4-5 at baseline, and those who had undergone renal transplant before exposure. Maximum follow-up was 12 years. Data were provided by the University of Dundee Health Informatics Centre, who have access to health-related population-based datasets containing data for every patient registered with a regional family doctor. Each patient has a unique ten-digit identifier, the Community Health Index, enabling us to link laboratory tests, dispensed community prescriptions, Scottish Morbidity Records, and mortality records to the patient. All data were anonymised according to Health Informatics Centre standard operating procedures. The primary outcome was the change per year in the eGFR, adjusted for age, sex, and baseline eGFR, and analysed by random coefficient models.

FINDINGS

1120 patients (305 exposed to lithium and 815 to comparator drugs) qualified for inclusion, providing 13 963 eGFR values over 12 years. The mean duration of exposure to lithium was 55 months (SD 42; range 6-144). Mean annual decline in eGFR (adjusted for age, sex, and baseline eGFR) was 1·3 mL/min per 1·73 m(2) (SE 0·2) in the lithium group, which did not differ significantly to that in the comparator group (0·9 mL/min/1·73 m(2) [SE 0·15]). After adjustment for additional confounders, the monthly decline in eGFR attributable to lithium exposure amounted to 0·02 mL/min per 1·73 m(2) (SE 0·02, p=0·30). As a post-hoc secondary outcome, we estimated the annual decline in eGFR for the lithium group to be 1·0 mL/min per 1·73 m(2) (SE 0·2), which again did not differ significantly to that in the comparator group (0·4 mL/min/1·73 m(2) [SE 0·2]. Modelling identified significant predictors for eGFR decline as age, baseline eGFR, comorbidities, co-prescriptions of nephrotoxic drugs, and episodes of lithium toxicity; however, duration of exposure to lithium and mean serum lithium level were not significant predictors for eGFR decline.

INTERPRETATION

Our analysis suggests no effect of stable lithium maintenance therapy (lithium levels in therapeutic range) on the rate of change in eGFR over time. Our results therefore contradict the idea that long-term lithium therapy is associated with nephrotoxicity in the absence of episodes of acute intoxication and that duration of therapy and cumulative dose are the major determinants of toxicity.

FUNDING

None.

Temporal association as a prerequisite factor of valsartan-induced lithium toxicity

OBJECTIVES

Lithium is often the mood stabilizer of choice for the treatment of type I bipolar disorder. However, side effects as well as the narrow therapeutic dosing range often complicate its use. Lithium toxicity can be fatal and its serum level needs to be closely monitored, especially at the time of introduction and titration, or whenever combined with potentially interacting drugs, such as inhibitors of angiotensin-converting enzyme (ACE-I) or angiotensin receptor 1 (AT1 ) blockers. ACE-I and AT1 blockers can increase serum lithium levels, leading to acute lithium toxicity upon their introduction or titration.

METHODS

Here, we report a case of lithium toxicity during concomitant treatment with valsartan, an AT1 blocker, in a patient who previously displayed a stable serum lithium level. The patient was observed for a few weeks and the serum lithium concentration was measured regularly.

RESULTS

In contrast to previous reports, the toxicity in our patient occurred not upon introduction or titration of lithium or valsartan but after subtle modifications in daily dosing schedule for lithium. Just before the onset of toxicity, lithium had been split into two doses, whereby half of the lithium daily dose was administrated concomitantly with valsartan. We presumed that this combination had led to simultaneous concentration peaks of valsartan and lithium, promoting lithium retention within a sharp time window.

CONCLUSIONS

Our observation points to the need for caution not only during the introduction and titration of ACE-I/AT1 blockers in lithium-treated patients, but also whenever the temporal pattern of drug administration is modified.

Age as a determinant of instability of serum lithium concentrations

BACKGROUND

Lithium is used both in bipolar disorder and as augmentation in treatment-resistant unipolar depression. Long-term treatment is often indicated. Pharmacokinetic and pharmacodynamic changes in older age, as well as increasing comorbidities and polypharmacy, could result in instability of serum lithium concentrations. In this study, several parameters, considered proxy for instability, were compared between age groups. These parameters were derived from studies involving oral anticoagulants.

METHODS

A retrospective study (1995-2004) was conducted using serum lithium concentrations from the laboratories of 3 hospitals in the Netherlands; 759 patients treated with lithium, 40 years or older, with at least 2 years' follow-up were identified. They were divided into 4 age groups: 40-49, 50-59, 60-69, and 70+ years; the youngest group was used as a reference group. The variance growth rate and percentage of time below, in, and above treatment range are all proxies for instability. They were analyzed between the age categories.

RESULTS

There was no significant difference for these variables between the reference group and the older age groups. In a subgroup of 454 patients, the parameters considered as proxy for instability during titration, number of days and number of serum lithium concentration measurements during titration, were evaluated; no significant difference was found between the age groups. In a small group of 117 patients, titration and maintenance treatment for at least 2 years could be analyzed separately. Also in this group, there was no difference between the age groups.

CONCLUSIONS

Age is not a determinant of serum lithium concentration instability. Therefore, age is not a reason to not initiate or discontinue lithium therapy.

Mood-dependent changes of serum lithium concentration in a rapid cycling patient maintained on stable doses of lithium carbonate

OBJECTIVE

Serum lithium levels may be influenced by mood state. We report on a 58-year-old female patient suffering from rapid cycling bipolar disorder. Her serum lithium levels varied greatly, despite stable medication.

METHODS

The patient was observed over a one-year period.

RESULTS

The patient received a stable medication of lithium carbonate (450 mg), valproate (1500 mg), and clozapine (200 mg). Investigating mood and serum lithium levels over one year revealed six manic and six depressive phases. The mean lithium serum level was 0.67 mmol/L in the depressive states, 0.39 mmol/L in the manic states (t = 4.11, p = 0.001 versus depression), and 0.40 mmol/L in the euthymic states (t = 3.58, p = 0.003 versus depression). Noncompliance was ruled out. The patient gained up to 8 kg during manic phases, accompanied by pretibial edema.

CONCLUSIONS

Changes in serum lithium concentration are probably not caused by altered lithium, but by water metabolism. During mania, body water increases, leading to dilution and therefore a reduction in serum lithium levels. As there is no proof for any other known cause of hypervolemia, we propose the hypothesis that the increase in body water is due to a variant of idiopathic edema.

Epidemiology and characteristics of adverse drug reactions caused by drug-drug interactions

INTRODUCTION

Drug-drug interactions (DDIs) arise in numerous different ways, involving pharmacokinetic or pharmacodynamic mechanisms. Adverse drug reactions are a possible consequence of DDIs and health operators are often unaware of the clinical risks of certain drug combinations. Many papers on drug interactions have been published in recent years, but most of them focused on potential DDIs while few studies have been conducted on actual interactions.

AREAS COVERED

This paper reviews the epidemiology of actual DDIs in outpatients as well as in hospital settings and in spontaneous reporting databases. The incidence of actual DDIs is consistently lower than that of potential DDIs. However, the absolute number of patients involved is high, representing a significant proportion of adverse drug reactions. The importance of risk factors such as age, polypharmacy and genetic polymorphisms is also evaluated. The relevance and efficacy of tools for recognizing and preventing DDIs are discussed.

EXPERT OPINION

Potential DDIs far outnumber actual drug interactions. The potential for an adverse interaction to occur is often theoretical, and clinically important adverse effects occur only in the presence of specific risk factors. Several studies have shown the efficacy of computers in early detection of DDIs. However, a correct risk-benefit evaluation by the prescribing physician, together with a careful clinical, physiological and biochemical monitoring of patients, is essential. Future directions of drug interaction research include the increasing importance of pharmacogenetics in preventing DDIs and the evaluation of interactions with biological drugs.

Toward the optimal clinical use of the fraction excretion of solutes in oliguric azotemia

While the fractional excretion of solutes have long been considered excellent research tools to investigate tubular physiology, their clinical use has become common over the last 40 years in the diagnoses of many disorders; however, none have reached the clinical utility of the fractional excretion of sodium in the ability to distinguish pre-renal azotemia from acute tubular necrosis. Nevertheless, there are many drugs and medical conditions that interfere with that utility and recently other solutes, including urea, uric acid and lithium, have been recently investigated to improve the diagnostic ability in clinical situations where the fractional excretion of sodium is known to be unreliable. We review the tubular physiology of these solutes and show how the differences in tubular physiology might be exploited to develop a strategy for their optimal clinical use.

Review of lithium effects on brain and blood

Clinicians have long used lithium to treat manic depression. They have also observed that lithium causes granulocytosis and lymphopenia while it enhances immunological activities of monocytes and lymphocytes. In fact, clinicians have long used lithium to treat granulocytopenia resulting from radiation and chemotherapy, to boost immunoglobulins after vaccination, and to enhance natural killer activity. Recent studies revealed a mechanism that ties together these disparate effects of lithium. Lithium acts through multiple pathways to inhibit glycogen synthetase kinase-3beta (GSK3 beta). This enzyme phosphorylates and inhibits nuclear factors that turn on cell growth and protection programs, including the nuclear factor of activated T cells (NFAT) and WNT/beta-catenin. In animals, lithium upregulates neurotrophins, including brain-derived neurotrophic factor (BDNF), nerve growth factor, neurotrophin-3 (NT3), as well as receptors to these growth factors in brain. Lithium also stimulates proliferation of stem cells, including bone marrow and neural stem cells in the subventricular zone, striatum, and forebrain. The stimulation of endogenous neural stem cells may explain why lithium increases brain cell density and volume in patients with bipolar disorders. Lithium also increases brain concentrations of the neuronal markers n-acetyl-aspartate and myoinositol. Lithium also remarkably protects neurons against glutamate, seizures, and apoptosis due to a wide variety of neurotoxins. The effective dose range for lithium is 0.6-1.0 mM in serum and >1.5 mM may be toxic. Serum lithium levels of 1.5-2.0 mM may have mild and reversible toxic effects on kidney, liver, heart, and glands. Serum levels of >2 mM may be associated with neurological symptoms, including cerebellar dysfunction. Prolonged lithium intoxication >2 mM can cause permanent brain damage. Lithium has low mutagenic and carcinogenic risk. Lithium is still the most effective therapy for depression. It "cures" a third of the patients with manic depression, improves the lives of about a third, and is ineffective in about a third. Recent studies suggest that some anticonvulsants (i.e., valproate, carbamapazine, and lamotrigene) may be useful in patients that do not respond to lithium. Lithium has been reported to be beneficial in animal models of brain injury, stroke, Alzheimer's, Huntington's, and Parkinson's diseases, amyotrophic lateral sclerosis (ALS), spinal cord injury, and other conditions. Clinical trials assessing the effects of lithium are under way. A recent clinical trial suggests that lithium stops the progression of ALS.

Lithium Toxicity Secondary to Lithium—Losartan Interaction

Objective:

To report a case of lithium toxicity following lithium and losartan coadministration in a diabetic patient.

Case Summary:

A 61-year-old white male with a history significant for bipolar disorder, hypertension, and diabetes was admitted to the Veterans Affairs Medical Center—based Nursing Home Care Unit for long-term intravenous antibiotic therapy for osteomyelitis. He developed lithium toxicity at a dose previously tolerated (1,350 mg/day) following administration of losartan 50 mg on the day before and day of evidence of toxicity. The drugs had been used concurrently prior to admission without evidence of toxicity; however, adherence to treatment could not be confirmed and concurrent dehydration may have been a contributing factor. Lithium toxicity was evidenced by irritability, tremors, confusion, and disorientation. Results of laboratory studies were significant for an elevated lithium concentration, hyponatremia, and slight elevations of serum creatinine and blood urea nitrogen. All other laboratory values were within normal limits.

Discussion:

Losartan, an angiotensin-receptor blocker (ARB), is commonly used for treatment of hypertension and heart failure as well as for renoprotection in diabetic patients. It has been shown to interact with lithium, resulting in lithium intoxication, most likely as a result of natriuresis leading to hyponatremia. Hyponatremia and a decrease in the glomerular filtration rate through the action of both angiotensin-converting enzyme inhibitors and ARBs enhance the renal tubular reabsorption of lithium, thus leading to potentially toxic serum concentrations of lithium. An objective causality assessment revealed that the interaction was probable.

Conclusions:

The temporal fashion in which the episode occurred indicated that a lithium—losartan interaction was probably the cause of lithium toxicity in this patient. Clinicians need to be aware of potential lithium—ARB interactions resulting in an increased risk of lithium toxicity associated with concurrent use of these drugs.

Effect of chronic lithium administration on endothelium-dependent relaxation of rat mesenteric bed: role of nitric oxide

The mechanism of action of lithium, an effective treatment for bipolar disease, is still unknown. In this study, the mesenteric vascular beds of control rats and rats that were chronically treated with lithium were prepared by the McGregor method, and the mesenteric vascular bed vasorelaxation responses were examined. NADPH-diaphorase histochemistry was used to determine the activity of NOS (nitric oxide synthase) in mesenteric vascular beds. We demonstrated that ACh-induced vasorelaxation increased in the mesenteric vascular bed of rats treated with lithium. Acute Nο-nitro-l-arginine methyl ester (l-NAME) administration in the medium blocked ACh-induced vasorelaxation in the control group more effectively than in lithium-treated rats, while the vasorelaxant response to sodium nitroprusside, a NO donor, was not different between lithium-treated and control groups. Acute aminoguanidine administration blocked ACh-induced vasorelaxation of lithium-treated rats, but had no effect in the control rats. Furthermore, NOS activity, determined by NADPH-diaphorase staining, was significantly greater in the mesenteric vascular beds from chronic lithium-treated rats than in those from control rats. These data suggest that the enhanced ACh-induced endothelium-derived vasorelaxation in rat mesenteric bed from chronic lithium-treated rats might be associated with increased NOS activity, likely via iNOS. Simultaneous acute l-NAME and indomethacin administration suggests the possible upregulation of EDHF (endothelium-derived hyperpolarizing factor) in lithium-treated rats.

The impact of environmental temperature on lithium serum levels

OBJECTIVES

Three studies have reported a seasonal variation in lithium serum levels, with higher levels during summer. Our objective was to investigate the impact of actual environmental temperature on lithium serum levels.

METHODS

A retrospective study was conducted using available records of lithium serum levels for the period between January 1995 and July 2004, obtained from three large teaching hospitals in The Netherlands. Lithium serum levels were linked to season and average daily temperature data obtained from the Royal Netherlands Meteorological Institute. An analysis was performed on all lithium serum levels not accounting for the intra-individual dependency of lithium serum levels. The association between season, temperature and both absolute lithium serum level and the frequency of potentially toxic serum levels was investigated. A mixed model analysis, accounting for intra-individual dependency of lithium serum levels, was performed.

RESULTS

A total of 41,102 lithium serum levels (3,054 patients) were included. A significant difference in mean lithium serum levels across seasons (p < 0.001) and temperature categories (p = 0.001) was found, peaking in summer [0.761 mmol/L, +/- standard error of the mean (SEM) 0.002] and at temperatures of 15-20 degrees C [0.762 mmol/L (+/- SEM 0.005)], and at a minimum in winter [0.748 mmol/L (+/- SEM 0.002)] and at <0 degrees C [0.741 mmol/L (+/- SEM 0.005)]. The relative frequency of potentially toxic serum levels significantly differed between seasons (p = 0.023, highest in winter), but not between temperature categories (p = 0.481). A significant positive association for intra-individual lithium serum level and season (p < 0.001) and temperature (p < 0.001) was established.

CONCLUSIONS

Season and environmental temperature have a statistically significant but therapeutically irrelevant effect on lithium serum levels.