Lithium intoxication after administration of AT1 blockers

Drug Interactions with Lithium: An Update

Lithium has been used for the management of psychiatric illnesses for over 50 years and it continues to be regarded as a first-line agent for the treatment and prevention of bipolar disorder. Lithium possesses a narrow therapeutic index and comparatively minor alterations in plasma concentrations can have significant clinical sequelae. Several drug classes have been implicated in the development of lithium toxicity over the years, including diuretics and non-steroidal anti-inflammatory compounds, but much of the anecdotal and experimental evidence supporting these interactions is dated, and many newer medications and medication classes have been introduced during the intervening years. This review is intended to provide an update on the accumulated evidence documenting potential interactions with lithium, with a focus on pharmacokinetic insights gained within the last two decades. The clinical relevance and ramifications of these interactions are discussed.

A case of lithium intoxication induced by an antihypertensive angiotensin 1 subtype-specific angiotensin II receptor blocker in an elderly patient with bipolar disorder and hypertension

Lithium carbonate is considered to be a first-line treatment for bipolar disorder; however, this drug has a narrow therapeutic window, and lithium intoxication is commonly induced by various drugs interaction and situations. We herein report a case of lithium intoxication induced by the administration of an antihypertensive agent targeting the angiotensin 1 (AT1) subtype of the angiotensin II receptor in a 65-year-old woman with a 40-year history of bipolar disorder type 1, and 1-year history of essential hypertension. Her bipolar disorder had been well-controlled with 600 mg/day of lithium carbonate for more than 10 years. She was later diagnosed with hypertension and the AT1 receptor blocker, azilsartan was thereafter administrated on a daily basis. After 3 weeks of azilsartan administration, she presented with progressive action tremor and showed a gradual deterioration of her physical state. Four months after the start of azilsartan administration, she presented with alternating episodes of diarrhea and constipation. Two weeks before admission to our hospital, she presented with mild consciousness disturbances, myoclonus, truncal ataxia, and appetite loss. She was diagnosed to have lithium intoxication based on an elevated serum lithium concentration of 3.28 mEq/l.It is therefore important to evaluate the serum lithium concentration after the administration of antihypertensive agents, and consider lithium-antihypertensive agent interactions when selecting antihypertensive agents in elderly patients receiving long-term lithium carbonate treatment.

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.

Angiotensin receptor blockers for bipolar disorder

Studies have suggested that the brain renin angiotensin system (RAS) regulates cerebral flow, autonomic and hormonal systems, stress, innate immune response and behavior, being implicated in several brain disorders such as major depression, Parkinson's and Alzheimer's disease. The angiotensin II receptor subtype 1 (AT1R) is distributed in brain regions responsible for the control of stress response through peripheral and central sympathetic hyperactivation as well as in the hypothalamic paraventricular region, areas known for the release of several neurotransmitters related to inflammatory response facilitation. This relationship leads to the assumption that AT1R might be the receptor most related to the central deleterious actions of angiotensin II. New evidences from clinical studies have shown a possible role for RAS in the pathogenesis of bipolar disorder (BD), a multifactorial disorder with acknowledged presence of neuronal damage via oxidative stress in brain areas such as hippocampus, prefrontal cortex and striatum. Given the studies highlighting AT1R activation as a central pro-inflammatory pathway and, conversely, the involvement of inflammatory response in the pathogenesis of BD; this paper hypothesizes the use of AT1R antagonists for BD management and prevention of its neuroprogression, due to their anti-inflammatory and neuroprotective effects.

Potentially harmful drug-drug interactions in the elderly: a review

BACKGROUND

Elderly patients are vulnerable to drug interactions because of age-related physiologic changes, an increased risk for disease associated with aging, and the consequent increase in medication use.

OBJECTIVE

The purpose of this narrative review was to describe findings from rigorously designed observational cohort and case-control studies that have assessed specific drug interactions in elderly patients.

METHODS

The PubMed and International Pharmaceutical Abstracts databases were searched for studies published in English over the past 10 years (December 2000-December 2010) using relevant Medical Subject Headings terms (aged; aged, 80 and over; and drug interactions) and search terms (drug interaction and elderly). Search strategies were saved and repeated through September 2011 to ensure that the most recent relevant published articles were identified. Additional articles were found using a search of review articles and reference lists of the identified studies. Studies were included if they were observational cohort or case-control studies that reported specific adverse drug interactions, included patients aged ≥65 years, and evaluated clinically meaningful end points. Studies were excluded if they used less rigorous observational designs, assessed pharmacokinetic/pharmacodynamic properties, evaluated drug-nutrient or drug-disease interactions or interactions of drug combinations used for therapeutic benefit (eg, dual antiplatelet therapy), or had inconclusive evidence.

RESULTS

Seventeen studies met the inclusion criteria. Sixteen studies reported an elevated risk for hospitalization in older adults associated with adverse drug interactions. The drug interactions included: angiotensin-converting enzyme (ACE) inhibitors and potassium-sparing diuretics, ACE inhibitors or angiotensin receptor blockers and sulfamethoxazole/trimethoprim, benzodiazepines or zolpidem and interacting medications, calcium channel blockers and macrolide antibiotics, digoxin and macrolide antibiotics, lithium and loop diuretics or ACE inhibitors, phenytoin and sulfamethoxazole/trimethoprim, sulfonylureas and antimicrobial agents, theophylline and ciprofloxacin, and warfarin and antimicrobial agents or nonsteroidal anti-inflammatory drugs. One study reported the risk for breast cancer-related death as a function of paroxetine exposure among women treated with tamoxifen.

CONCLUSIONS

Several population-based studies have reported significant harm associated drug interactions in elderly patients. Increased awareness and interventions aimed at reducing exposure and minimizing the risks associated with potentially harmful drug combinations are needed.

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.

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.

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

OBJECTIVE

Lithium is a drug with a narrow therapeutic window. Concomitantly used medication is a potentially influencing factor of lithium serum concentrations. We conducted a multicentre retrospective case-control study with the aim of investigating lithium-related drug interactions as determinants of elevated lithium serum levels in daily clinical practice.

METHODS

Cases were patients with an increase of at least 50% in lithium serum concentrations resulting in an elevated lithium serum level of at least 1.3 mmol/L, and who were not suspected of a suicide attempt. Controls were patients who showed stable lithium serum levels within the therapeutic range. Use and start of non-steroidal anti-inflammatory drugs, diuretics, renin-angiotensin inhibitors, theophyllin and antibiotics were investigated as potential determinants of the elevated lithium serum levels. Irregularity in lithium dispensing pattern, change in lithium dosing regimen, age, gender, prescribing physician and laboratory parameters were investigated as potential confounders.

RESULTS

We included 51 cases and 51 controls in our study. Five (9.8%) controls and 15 (29.4%) cases used potentially interacting co-medication [OR of 3.83 (95%CI 1.28-11.48)]. Start of potentially interacting co-medication was observed in eight (15.7%) cases and in zero (0%) controls resulting in an OR of 20.13 (95% CI 1.13-359). After adjustment for co-medication, irregularity in lithium dispensing pattern, change in lithium dosing regimen, and age, the statistically significant association was lost. We report an OR of 2.70 (95% CI 0.78-9.31) for use of concomitant medication, with a large contribution of antibiotic agents, and an OR of 3.14 (95% CI 1.15-8.61) for irregularity in lithium dispensing pattern.

CONCLUSION

Use of co-medication, especially antibiotics, tends to be associated with elevated lithium serum levels.

Antihypertensive therapy: special focus on drug interactions

Today, the lifetime risk of patients aged 55-65 years to receive antihypertensive drugs approaches 60%. Yet, recent trials suggest that hypertension is not adequately controlled in the majority of patients. The prevalence of hypertension increases with advancing age, as does the prevalence of comorbid conditions and the total number of medications taken. Multi-drug therapy, advancing age and comorbid conditions are also key risk factors for adverse drug reactions and drug interactions. In this review, the authors evaluate the most frequently used antihypertensive drugs (diuretics, beta-adrenergic blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, angiotensin II receptor Type 1 blockers and alpha-adrenergic blockers) with special reference to pharmacodynamic and pharmacokinetic drug interactions. As the spectrum of drugs prescribed is constantly changing, safety yesterday does not imply safety today and safety today does not imply safety tomorrow. Furthermore, therapeutic efficacy should not be neglected over concerns regarding drug interactions. Many patients are at risk of clinically relevant drug interactions involving antihypertensive drugs but, presently, even more patients may be at risk of suffering from the consequences of their inadequately treated hypertension. In this respect, the authors discuss controversial viewpoints on the overall clinical relevance of drug interactions occurring at the level of cytochrome P450 metabolism.

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