Melvin G. McInnis, MD

Lithium is among the most effective therapies for bipolar disorder (BD), and enthusiasm for this simple molecule is waxing. The his­tory of lithium is fascinating,¹ and recent considerations include that this element, the third on the periodic table, has few, if any, indus­try champions. The recent renaissance is caused by a groundswell of appreciation for the clinical efficacy of lithium and an increasing num­ber of providers who are willing to manage patients with lithium.

Target: Bipolar disorder
The target illness for lithium is BD, a spectrum of mood disorders with characteristic features of unstable mood and affect. Shifts in mood include recurrent episodes of mania, which are pathologically ener­gized states with misguided volition and behavior with intoxicating euphoria (or irritability).^₂ Psychomotor activity is elevated and out of character; speech and body movements are revved up, with a dimin­ished need for sleep. The social, personal, and vocational consequences often are disastrous.

The most common mood state of BD is depression. Depressive episodes consist of pathologically compromised energy and volition with a slowing of bodily functions, most prominently cognition and concentration; a pervasive depressed or sad mood is common but not always present. Presence of mixed states, when features of depression and mania are present simultaneously, is one of the many challenges of treating BD; an elevated volitional or energized state may occur with a depressed, dysphoric mood.

Evidence for lithium
Efficacy studies of lithium have focused on managing mood disorders, treating mania and depression, and prevention or main­tenance care.³ Most were performed dur­ing the 1970s and 1980s,³ but recent studies have been comparing lithium with other mood stabilizers^4-7 and searching for a genetic basis for lithium response.^8-10 Other researchers have examined the use of lith­ium to prevent suicide.¹¹ Some have sug­gested a neuroprotective effect of lithium, which may have profound implications for neuropsychiatry if valid.^12-14 Results of additional studies, which are at differ­ent stages of completion, will clarify lith­ium use,^15,16 and characterize the genetic makeup of individuals who respond to lithium.¹⁷ The primary evidence for lith­ium, however, is for maintenance treat­ment of BD and for preventing manic and depressive episodes.

Biochemistry and physiology of lithium. The biochemical and physiological effects of lithium are complex, wide-ranging, and likely to affect hundreds, if not thou­sands, of genes and gene products. The mechanisms of action remain a focus of aca­demic pursuit (for a review of hypotheses related to these mechanisms see Goodwin and Jamison² and Can et al¹⁸) Lithium is involved in cell signaling pathways that involve complex molecular mechanisms of inter- and intracellular communica­tion¹⁹; some neural receptors are down-regulated²⁰ and others show inhibition,²¹ which is thought to be a mechanism of lithium. The hypothesized neuroprotective effect of lithium²² may be mediated through an increased level of brain-derived neuro­trophic factor in brain tissue.¹⁴ Recently, investigators using induced pluripotent stem cell derived neurons have shown that patterns of calcium-related cell signaling in bipolar neurons are affected specifically by lithium in the culture media.²³ There likely are many mechanisms through which lithi­um’s effects are mediated, including a series of dynamic pathways that vary over time and in reaction to the internal and external environments of the cell and person.

The lithium renaissance
In the past decade, there has been an increase in interest and use of lithium because clinicians recognize its efficacy and advantages and can monitor serum levels and gauge the patient’s response and side effects²⁴ against the lithium level. This is important because balancing effi­ cacy and side effects depends on the serum level. Efficacy often is not immediate, although side effects may emerge early. All systems of the body may show effects that could be related to lithium use. It is helpful to be aware of the side effects in chronolog­ical order, because some immediate effects may be associated with starting at higher dosages (Table 1). Common side effects in the short term include:

   • GI distress, such as nausea, vomiting, diarrhea, and abdominal discomfort
   • a fine neurologic tremor, which may be seen with accentuation upon deliber­ate movement
   • prominent thirst with polyuria
   • drowsiness and clouded thinking, which can be upsetting to the patient and family.

In the longer term, adverse effects on kidney and thyroid function are common. Management must include monitoring of the serum level.

Lithium is FDA-approved for acute and maintenance treatment of mania in BD. There are reports that discuss most vari­ants of mood disorders, including BD I, BD II, unipolar depression, rapid cycling, and even alcohol abuse.^25-29 Lithium could help manage mood dysregulation in the context of temperament and personal­ity.³⁰ There is evidence that lithium has an antidepressant effect31-33 and has shown efficacy as an adjunctive treatment for depression.^31-33 There are data that sug­gest that lithium, with its neuroprotective mechanisms, may prevent progression of mild cognitive impairment.³⁴

Is there an ideal lithium candidate?
Mood instability is the characteristic fea­ture of a lithium responder. The instability may be over the course of the day, such as a dysregulated temperament that often is associated with DSM-IV personality cat­egories, shorter-term fluctuations (within days with BD II), or in the context of epi­sodic shifts of mood states over weeks and months, which are characteristic of BD I. The hallmark of mood instability is fluctuation from depression to elevated mood states and charged emotions with increased energy.

The patient considered ideal for lith­ium treatment has BD I with recurrent severe euphoric manic episodes, absence of significant comorbid disorders such as substance abuse, and a family history of lithium response. However, any patient with a clinically significant and unstable mood disorder, regardless of the DSM diagnosis, should be considered for lith­ium treatment.

When considering a lithium trial for a patient with significant mood instability, it is critical to establish the target symptoms and behavior that will help you gauge the efficacy of the intervention. Measurement-based care utilizes clinician and self-report instruments to provide data on the ill­ness course and response to interven­tion. Commonly used clinician driven assessments include the Young Mania Rating Scale³⁵ and the Quick Inventory of Depressive Symptoms,³⁶ while the self-report assessments are the Patient Health Questionnaire³⁷ and the Altman Self- Rating Mania Scale.³⁸

During acute mania or depression, lithium often is used in combination with another medications such as an antipsy­chotic or antidepressant. Used in the out­patient and non-acute setting, lithium may be an “add-on” or monotherapy for pre­venting recurrence of episodes. Response in early acute manic symptoms are predic­tive of later response and remission.³⁹

Dosing strategies
An initial problem with lithium is side effects that emerge when beginning treat­ment, which may discourage the patient and family from using this agent. Starting with 150 mg/d for the first 2 or 3 doses is unlikely to produce any adverse effects and can show the patient that there is a high likelihood that he will be able to tol­erate the medication. Gradual titration over several days—or even weeks—to the target dosage and serum levels will enhance patient compliance. Rate of dos­age increase is best guided by tolerance to the medication. The general consensus is that lithium is most effective at levels of 0.6 to 0.8 mEq/L,⁴⁰ although a lower level (0.5 mEq/L) over a 2-year period also can be effective.⁴¹ Lithium may be used in to treat acute mania at higher serum levels (0.8 to 1.2 mEq/L), however, the acute phase often requires urgent management, usually with an antipsychotic.

Emerging consensus
Although there is a need to gather and analyze longer observational periods to clarify the clinical and biological charac­teristics of persons who respond to lith­ium, there are several points of consensus. Management will be guided by patient characteristics such as age, comorbidities, and other therapies. Most studies that address the effect of lithium level focus on high vs low serum levels. There are 3 cat­egories of lithium serum levels, low (<0.6 mEq/L), mid-range (0.6 to 0.8 mEq/L), and high (>0.8 mEq/L), each has risk-benefit considerations.

The LiTMUS study⁴² compared low-level lithium augmentation with opti­mized personal treatment without lithium. Both groups had similar outcomes but the lithium-treated group had significantly lower use of atypical antipsychotics. This may be important when considering the long-term risk of the metabolic syndrome because the tolerability and side-effect profile of lithium at lower levels is more favorable than that of atypical antipsy­chotics. As lithium levels increase, there seems to be concomitant increase in effi­cacy and side effects. Many patients will benefit with low-level lithium use; yet clearly some individuals require higher dosages for effective maintenance therapy.

Dosing and monitoring. In patients age >50 or those with comorbid medical conditions, use a lower level of lithium (<0.6 mEq/L). Most individuals with BD likely will benefit from the mid-range level strategy (0.6 to 0.8 mEq/L); however, there will be those who require a higher level. When beginning lithium, start at a low dosage (150 mg/d) and increase as tolerated to the desired serum level. With acute mania, temporary use of an antipsychotic will be required.

There are no tests available to determine whether a patient will do well at any of these lithium serum levels. Breakthrough mania in an adherent patient with a serum lithium level of 0.7 mEq/L indicates the need to obtain a higher lithium level. A major deficit in lithium research is the lack of long-term data (>5 years) on out­comes, clinical and biological features with lithium levels because of a lack of pharma­ceutical company support.^3,17 Monitoring mood symptoms using detailed mood charts, whether clinician-administered or self-reported, is an effective way to moni­tor outcomes, provided the clinician uses the same scales or methods to record a patient’s moods. If a patient wants to dis­continue lithium, taper the drug over an extended period (months) to minimize the likelihood of emerging manic or depressive episodes related to drug discontinuation.

Managing side effects
Consider lithium’s side effects in the con­text of their short-, intermediate-, and long-term presence (Table 2). Gradually increasing the lithium dosage often will prevent side effects that manifest in the short term. If side effects emerge at low dosages, proceed slowly with lithium and manage symptoms with other medica­tions. When a patient shows a change in side effects, obtain lithium and electrolytes levels; a change in mental status with con­fusion will require an acute lithium level.

A diary of symptoms or clinically rel­evant matters such as fluid intake or fre­quency of GI- or neurological-related events will help the clinician monitor the frequency and severity of side effects. The patient and clinician should not be dis­couraged by emerging side effects in the short term, because they may dissipate or become minimally intrusive.

Several strategies can alleviate immedi­ate GI effects, such as dosing with meals, enteric-coated formulations, multiple dose strategies, and short-term use of antidiar­rheal medicine as needed. Side effects that disrupt a patient’s fluid and electrolyte balance (diabetes insipidus) to the point of clouding mental status will require discon­tinuing the medication until mental sta­tus improves, then reconsideration of the treatment regime, which will include man­aging diabetes insipidus with amiloride. Managing side effects may require consulta­tion with specialty services. Likewise, some patients might experience neurologic side effects, such as profound tremor, that inter­feres with their ability to function. However, many side effects can be managed symp­tomatically with practical strategies (eg, a sugar-free lozenge for dry mouth or dysgeu­sia). Consider lower lithium dosages and serum levels because patients may experi­ence benefits with lower therapeutic levels.

Long-term side effects include decreased renal function, hypothyroidism, persistent tremor, and dermatologic effects of acne and alopecia. Monitor renal and thyroid function annually in stable patients and more frequently when making changes in the treatment plan.

Before discontinuing lithium, consider discussing the medical issues with a spe­cialist who has experience with complica­tions of lithium.

Bottom Line
Lithium is an effective and under used medication for managing bipolar disorder. Initial prejudices and side effects often deter patients and prescribers from proceeding with a therapeutic trial of lithium. Although the mid-range lithium level of 0.6 to 0.8 mEq/L is desirable, many patients will experience significant benefits with lower levels. Initial strategies include the use of low-dose preparations that are unlikely to have uncomfortable side effects.

Related Resources
• Andreasen A, Ellingrod VL. Lithium-induced diabetes in­sipidus: prevention and management. Current Psychiatry. 2013;12(7):42-45.
• Cipriani A, Hawton K, Stockton S, et al. Lithium in the pre­vention of suicide in mood disorders: updated system­atic review and meta-analysis. BMJ. 2013;346:f3646. doi: 10.1136/bmj.f3646.

Drug Brand Names
Amiloride • Midamor                Lithium • Eskalith, Lithobid

Disclosure
Dr. McInnis reports no financial relationship with any company whose products are mentioned in this article or with manufacturers of competing products.

Lithium is among the most effective therapies for bipolar disorder (BD), and enthusiasm for this simple molecule is waxing. The his­tory of lithium is fascinating,¹ and recent considerations include that this element, the third on the periodic table, has few, if any, indus­try champions. The recent renaissance is caused by a groundswell of appreciation for the clinical efficacy of lithium and an increasing num­ber of providers who are willing to manage patients with lithium.

Target: Bipolar disorder
The target illness for lithium is BD, a spectrum of mood disorders with characteristic features of unstable mood and affect. Shifts in mood include recurrent episodes of mania, which are pathologically ener­gized states with misguided volition and behavior with intoxicating euphoria (or irritability).^₂ Psychomotor activity is elevated and out of character; speech and body movements are revved up, with a dimin­ished need for sleep. The social, personal, and vocational consequences often are disastrous.

The most common mood state of BD is depression. Depressive episodes consist of pathologically compromised energy and volition with a slowing of bodily functions, most prominently cognition and concentration; a pervasive depressed or sad mood is common but not always present. Presence of mixed states, when features of depression and mania are present simultaneously, is one of the many challenges of treating BD; an elevated volitional or energized state may occur with a depressed, dysphoric mood.

Evidence for lithium
Efficacy studies of lithium have focused on managing mood disorders, treating mania and depression, and prevention or main­tenance care.³ Most were performed dur­ing the 1970s and 1980s,³ but recent studies have been comparing lithium with other mood stabilizers^4-7 and searching for a genetic basis for lithium response.^8-10 Other researchers have examined the use of lith­ium to prevent suicide.¹¹ Some have sug­gested a neuroprotective effect of lithium, which may have profound implications for neuropsychiatry if valid.^12-14 Results of additional studies, which are at differ­ent stages of completion, will clarify lith­ium use,^15,16 and characterize the genetic makeup of individuals who respond to lithium.¹⁷ The primary evidence for lith­ium, however, is for maintenance treat­ment of BD and for preventing manic and depressive episodes.

Biochemistry and physiology of lithium. The biochemical and physiological effects of lithium are complex, wide-ranging, and likely to affect hundreds, if not thou­sands, of genes and gene products. The mechanisms of action remain a focus of aca­demic pursuit (for a review of hypotheses related to these mechanisms see Goodwin and Jamison² and Can et al¹⁸) Lithium is involved in cell signaling pathways that involve complex molecular mechanisms of inter- and intracellular communica­tion¹⁹; some neural receptors are down-regulated²⁰ and others show inhibition,²¹ which is thought to be a mechanism of lithium. The hypothesized neuroprotective effect of lithium²² may be mediated through an increased level of brain-derived neuro­trophic factor in brain tissue.¹⁴ Recently, investigators using induced pluripotent stem cell derived neurons have shown that patterns of calcium-related cell signaling in bipolar neurons are affected specifically by lithium in the culture media.²³ There likely are many mechanisms through which lithi­um’s effects are mediated, including a series of dynamic pathways that vary over time and in reaction to the internal and external environments of the cell and person.

The lithium renaissance
In the past decade, there has been an increase in interest and use of lithium because clinicians recognize its efficacy and advantages and can monitor serum levels and gauge the patient’s response and side effects²⁴ against the lithium level. This is important because balancing effi­ cacy and side effects depends on the serum level. Efficacy often is not immediate, although side effects may emerge early. All systems of the body may show effects that could be related to lithium use. It is helpful to be aware of the side effects in chronolog­ical order, because some immediate effects may be associated with starting at higher dosages (Table 1). Common side effects in the short term include:

   • GI distress, such as nausea, vomiting, diarrhea, and abdominal discomfort
   • a fine neurologic tremor, which may be seen with accentuation upon deliber­ate movement
   • prominent thirst with polyuria
   • drowsiness and clouded thinking, which can be upsetting to the patient and family.

In the longer term, adverse effects on kidney and thyroid function are common. Management must include monitoring of the serum level.

Lithium is FDA-approved for acute and maintenance treatment of mania in BD. There are reports that discuss most vari­ants of mood disorders, including BD I, BD II, unipolar depression, rapid cycling, and even alcohol abuse.^25-29 Lithium could help manage mood dysregulation in the context of temperament and personal­ity.³⁰ There is evidence that lithium has an antidepressant effect31-33 and has shown efficacy as an adjunctive treatment for depression.^31-33 There are data that sug­gest that lithium, with its neuroprotective mechanisms, may prevent progression of mild cognitive impairment.³⁴

Is there an ideal lithium candidate?
Mood instability is the characteristic fea­ture of a lithium responder. The instability may be over the course of the day, such as a dysregulated temperament that often is associated with DSM-IV personality cat­egories, shorter-term fluctuations (within days with BD II), or in the context of epi­sodic shifts of mood states over weeks and months, which are characteristic of BD I. The hallmark of mood instability is fluctuation from depression to elevated mood states and charged emotions with increased energy.

The patient considered ideal for lith­ium treatment has BD I with recurrent severe euphoric manic episodes, absence of significant comorbid disorders such as substance abuse, and a family history of lithium response. However, any patient with a clinically significant and unstable mood disorder, regardless of the DSM diagnosis, should be considered for lith­ium treatment.

When considering a lithium trial for a patient with significant mood instability, it is critical to establish the target symptoms and behavior that will help you gauge the efficacy of the intervention. Measurement-based care utilizes clinician and self-report instruments to provide data on the ill­ness course and response to interven­tion. Commonly used clinician driven assessments include the Young Mania Rating Scale³⁵ and the Quick Inventory of Depressive Symptoms,³⁶ while the self-report assessments are the Patient Health Questionnaire³⁷ and the Altman Self- Rating Mania Scale.³⁸

During acute mania or depression, lithium often is used in combination with another medications such as an antipsy­chotic or antidepressant. Used in the out­patient and non-acute setting, lithium may be an “add-on” or monotherapy for pre­venting recurrence of episodes. Response in early acute manic symptoms are predic­tive of later response and remission.³⁹

Dosing strategies
An initial problem with lithium is side effects that emerge when beginning treat­ment, which may discourage the patient and family from using this agent. Starting with 150 mg/d for the first 2 or 3 doses is unlikely to produce any adverse effects and can show the patient that there is a high likelihood that he will be able to tol­erate the medication. Gradual titration over several days—or even weeks—to the target dosage and serum levels will enhance patient compliance. Rate of dos­age increase is best guided by tolerance to the medication. The general consensus is that lithium is most effective at levels of 0.6 to 0.8 mEq/L,⁴⁰ although a lower level (0.5 mEq/L) over a 2-year period also can be effective.⁴¹ Lithium may be used in to treat acute mania at higher serum levels (0.8 to 1.2 mEq/L), however, the acute phase often requires urgent management, usually with an antipsychotic.

Emerging consensus
Although there is a need to gather and analyze longer observational periods to clarify the clinical and biological charac­teristics of persons who respond to lith­ium, there are several points of consensus. Management will be guided by patient characteristics such as age, comorbidities, and other therapies. Most studies that address the effect of lithium level focus on high vs low serum levels. There are 3 cat­egories of lithium serum levels, low (<0.6 mEq/L), mid-range (0.6 to 0.8 mEq/L), and high (>0.8 mEq/L), each has risk-benefit considerations.

The LiTMUS study⁴² compared low-level lithium augmentation with opti­mized personal treatment without lithium. Both groups had similar outcomes but the lithium-treated group had significantly lower use of atypical antipsychotics. This may be important when considering the long-term risk of the metabolic syndrome because the tolerability and side-effect profile of lithium at lower levels is more favorable than that of atypical antipsy­chotics. As lithium levels increase, there seems to be concomitant increase in effi­cacy and side effects. Many patients will benefit with low-level lithium use; yet clearly some individuals require higher dosages for effective maintenance therapy.

Dosing and monitoring. In patients age >50 or those with comorbid medical conditions, use a lower level of lithium (<0.6 mEq/L). Most individuals with BD likely will benefit from the mid-range level strategy (0.6 to 0.8 mEq/L); however, there will be those who require a higher level. When beginning lithium, start at a low dosage (150 mg/d) and increase as tolerated to the desired serum level. With acute mania, temporary use of an antipsychotic will be required.

There are no tests available to determine whether a patient will do well at any of these lithium serum levels. Breakthrough mania in an adherent patient with a serum lithium level of 0.7 mEq/L indicates the need to obtain a higher lithium level. A major deficit in lithium research is the lack of long-term data (>5 years) on out­comes, clinical and biological features with lithium levels because of a lack of pharma­ceutical company support.^3,17 Monitoring mood symptoms using detailed mood charts, whether clinician-administered or self-reported, is an effective way to moni­tor outcomes, provided the clinician uses the same scales or methods to record a patient’s moods. If a patient wants to dis­continue lithium, taper the drug over an extended period (months) to minimize the likelihood of emerging manic or depressive episodes related to drug discontinuation.

Managing side effects
Consider lithium’s side effects in the con­text of their short-, intermediate-, and long-term presence (Table 2). Gradually increasing the lithium dosage often will prevent side effects that manifest in the short term. If side effects emerge at low dosages, proceed slowly with lithium and manage symptoms with other medica­tions. When a patient shows a change in side effects, obtain lithium and electrolytes levels; a change in mental status with con­fusion will require an acute lithium level.

A diary of symptoms or clinically rel­evant matters such as fluid intake or fre­quency of GI- or neurological-related events will help the clinician monitor the frequency and severity of side effects. The patient and clinician should not be dis­couraged by emerging side effects in the short term, because they may dissipate or become minimally intrusive.

Several strategies can alleviate immedi­ate GI effects, such as dosing with meals, enteric-coated formulations, multiple dose strategies, and short-term use of antidiar­rheal medicine as needed. Side effects that disrupt a patient’s fluid and electrolyte balance (diabetes insipidus) to the point of clouding mental status will require discon­tinuing the medication until mental sta­tus improves, then reconsideration of the treatment regime, which will include man­aging diabetes insipidus with amiloride. Managing side effects may require consulta­tion with specialty services. Likewise, some patients might experience neurologic side effects, such as profound tremor, that inter­feres with their ability to function. However, many side effects can be managed symp­tomatically with practical strategies (eg, a sugar-free lozenge for dry mouth or dysgeu­sia). Consider lower lithium dosages and serum levels because patients may experi­ence benefits with lower therapeutic levels.

Long-term side effects include decreased renal function, hypothyroidism, persistent tremor, and dermatologic effects of acne and alopecia. Monitor renal and thyroid function annually in stable patients and more frequently when making changes in the treatment plan.

Before discontinuing lithium, consider discussing the medical issues with a spe­cialist who has experience with complica­tions of lithium.

Bottom Line
Lithium is an effective and under used medication for managing bipolar disorder. Initial prejudices and side effects often deter patients and prescribers from proceeding with a therapeutic trial of lithium. Although the mid-range lithium level of 0.6 to 0.8 mEq/L is desirable, many patients will experience significant benefits with lower levels. Initial strategies include the use of low-dose preparations that are unlikely to have uncomfortable side effects.

Related Resources
• Andreasen A, Ellingrod VL. Lithium-induced diabetes in­sipidus: prevention and management. Current Psychiatry. 2013;12(7):42-45.
• Cipriani A, Hawton K, Stockton S, et al. Lithium in the pre­vention of suicide in mood disorders: updated system­atic review and meta-analysis. BMJ. 2013;346:f3646. doi: 10.1136/bmj.f3646.

Drug Brand Names
Amiloride • Midamor                Lithium • Eskalith, Lithobid

Disclosure
Dr. McInnis reports no financial relationship with any company whose products are mentioned in this article or with manufacturers of competing products.

Lithium is among the most effective therapies for bipolar disorder (BD), and enthusiasm for this simple molecule is waxing. The his­tory of lithium is fascinating,¹ and recent considerations include that this element, the third on the periodic table, has few, if any, indus­try champions. The recent renaissance is caused by a groundswell of appreciation for the clinical efficacy of lithium and an increasing num­ber of providers who are willing to manage patients with lithium.

Target: Bipolar disorder
The target illness for lithium is BD, a spectrum of mood disorders with characteristic features of unstable mood and affect. Shifts in mood include recurrent episodes of mania, which are pathologically ener­gized states with misguided volition and behavior with intoxicating euphoria (or irritability).^₂ Psychomotor activity is elevated and out of character; speech and body movements are revved up, with a dimin­ished need for sleep. The social, personal, and vocational consequences often are disastrous.

The most common mood state of BD is depression. Depressive episodes consist of pathologically compromised energy and volition with a slowing of bodily functions, most prominently cognition and concentration; a pervasive depressed or sad mood is common but not always present. Presence of mixed states, when features of depression and mania are present simultaneously, is one of the many challenges of treating BD; an elevated volitional or energized state may occur with a depressed, dysphoric mood.

Evidence for lithium
Efficacy studies of lithium have focused on managing mood disorders, treating mania and depression, and prevention or main­tenance care.³ Most were performed dur­ing the 1970s and 1980s,³ but recent studies have been comparing lithium with other mood stabilizers^4-7 and searching for a genetic basis for lithium response.^8-10 Other researchers have examined the use of lith­ium to prevent suicide.¹¹ Some have sug­gested a neuroprotective effect of lithium, which may have profound implications for neuropsychiatry if valid.^12-14 Results of additional studies, which are at differ­ent stages of completion, will clarify lith­ium use,^15,16 and characterize the genetic makeup of individuals who respond to lithium.¹⁷ The primary evidence for lith­ium, however, is for maintenance treat­ment of BD and for preventing manic and depressive episodes.

Biochemistry and physiology of lithium. The biochemical and physiological effects of lithium are complex, wide-ranging, and likely to affect hundreds, if not thou­sands, of genes and gene products. The mechanisms of action remain a focus of aca­demic pursuit (for a review of hypotheses related to these mechanisms see Goodwin and Jamison² and Can et al¹⁸) Lithium is involved in cell signaling pathways that involve complex molecular mechanisms of inter- and intracellular communica­tion¹⁹; some neural receptors are down-regulated²⁰ and others show inhibition,²¹ which is thought to be a mechanism of lithium. The hypothesized neuroprotective effect of lithium²² may be mediated through an increased level of brain-derived neuro­trophic factor in brain tissue.¹⁴ Recently, investigators using induced pluripotent stem cell derived neurons have shown that patterns of calcium-related cell signaling in bipolar neurons are affected specifically by lithium in the culture media.²³ There likely are many mechanisms through which lithi­um’s effects are mediated, including a series of dynamic pathways that vary over time and in reaction to the internal and external environments of the cell and person.

The lithium renaissance
In the past decade, there has been an increase in interest and use of lithium because clinicians recognize its efficacy and advantages and can monitor serum levels and gauge the patient’s response and side effects²⁴ against the lithium level. This is important because balancing effi­ cacy and side effects depends on the serum level. Efficacy often is not immediate, although side effects may emerge early. All systems of the body may show effects that could be related to lithium use. It is helpful to be aware of the side effects in chronolog­ical order, because some immediate effects may be associated with starting at higher dosages (Table 1). Common side effects in the short term include:

   • GI distress, such as nausea, vomiting, diarrhea, and abdominal discomfort
   • a fine neurologic tremor, which may be seen with accentuation upon deliber­ate movement
   • prominent thirst with polyuria
   • drowsiness and clouded thinking, which can be upsetting to the patient and family.

In the longer term, adverse effects on kidney and thyroid function are common. Management must include monitoring of the serum level.

Lithium is FDA-approved for acute and maintenance treatment of mania in BD. There are reports that discuss most vari­ants of mood disorders, including BD I, BD II, unipolar depression, rapid cycling, and even alcohol abuse.^25-29 Lithium could help manage mood dysregulation in the context of temperament and personal­ity.³⁰ There is evidence that lithium has an antidepressant effect31-33 and has shown efficacy as an adjunctive treatment for depression.^31-33 There are data that sug­gest that lithium, with its neuroprotective mechanisms, may prevent progression of mild cognitive impairment.³⁴

Is there an ideal lithium candidate?
Mood instability is the characteristic fea­ture of a lithium responder. The instability may be over the course of the day, such as a dysregulated temperament that often is associated with DSM-IV personality cat­egories, shorter-term fluctuations (within days with BD II), or in the context of epi­sodic shifts of mood states over weeks and months, which are characteristic of BD I. The hallmark of mood instability is fluctuation from depression to elevated mood states and charged emotions with increased energy.

The patient considered ideal for lith­ium treatment has BD I with recurrent severe euphoric manic episodes, absence of significant comorbid disorders such as substance abuse, and a family history of lithium response. However, any patient with a clinically significant and unstable mood disorder, regardless of the DSM diagnosis, should be considered for lith­ium treatment.

When considering a lithium trial for a patient with significant mood instability, it is critical to establish the target symptoms and behavior that will help you gauge the efficacy of the intervention. Measurement-based care utilizes clinician and self-report instruments to provide data on the ill­ness course and response to interven­tion. Commonly used clinician driven assessments include the Young Mania Rating Scale³⁵ and the Quick Inventory of Depressive Symptoms,³⁶ while the self-report assessments are the Patient Health Questionnaire³⁷ and the Altman Self- Rating Mania Scale.³⁸

During acute mania or depression, lithium often is used in combination with another medications such as an antipsy­chotic or antidepressant. Used in the out­patient and non-acute setting, lithium may be an “add-on” or monotherapy for pre­venting recurrence of episodes. Response in early acute manic symptoms are predic­tive of later response and remission.³⁹

Dosing strategies
An initial problem with lithium is side effects that emerge when beginning treat­ment, which may discourage the patient and family from using this agent. Starting with 150 mg/d for the first 2 or 3 doses is unlikely to produce any adverse effects and can show the patient that there is a high likelihood that he will be able to tol­erate the medication. Gradual titration over several days—or even weeks—to the target dosage and serum levels will enhance patient compliance. Rate of dos­age increase is best guided by tolerance to the medication. The general consensus is that lithium is most effective at levels of 0.6 to 0.8 mEq/L,⁴⁰ although a lower level (0.5 mEq/L) over a 2-year period also can be effective.⁴¹ Lithium may be used in to treat acute mania at higher serum levels (0.8 to 1.2 mEq/L), however, the acute phase often requires urgent management, usually with an antipsychotic.

Emerging consensus
Although there is a need to gather and analyze longer observational periods to clarify the clinical and biological charac­teristics of persons who respond to lith­ium, there are several points of consensus. Management will be guided by patient characteristics such as age, comorbidities, and other therapies. Most studies that address the effect of lithium level focus on high vs low serum levels. There are 3 cat­egories of lithium serum levels, low (<0.6 mEq/L), mid-range (0.6 to 0.8 mEq/L), and high (>0.8 mEq/L), each has risk-benefit considerations.

The LiTMUS study⁴² compared low-level lithium augmentation with opti­mized personal treatment without lithium. Both groups had similar outcomes but the lithium-treated group had significantly lower use of atypical antipsychotics. This may be important when considering the long-term risk of the metabolic syndrome because the tolerability and side-effect profile of lithium at lower levels is more favorable than that of atypical antipsy­chotics. As lithium levels increase, there seems to be concomitant increase in effi­cacy and side effects. Many patients will benefit with low-level lithium use; yet clearly some individuals require higher dosages for effective maintenance therapy.

Dosing and monitoring. In patients age >50 or those with comorbid medical conditions, use a lower level of lithium (<0.6 mEq/L). Most individuals with BD likely will benefit from the mid-range level strategy (0.6 to 0.8 mEq/L); however, there will be those who require a higher level. When beginning lithium, start at a low dosage (150 mg/d) and increase as tolerated to the desired serum level. With acute mania, temporary use of an antipsychotic will be required.

There are no tests available to determine whether a patient will do well at any of these lithium serum levels. Breakthrough mania in an adherent patient with a serum lithium level of 0.7 mEq/L indicates the need to obtain a higher lithium level. A major deficit in lithium research is the lack of long-term data (>5 years) on out­comes, clinical and biological features with lithium levels because of a lack of pharma­ceutical company support.^3,17 Monitoring mood symptoms using detailed mood charts, whether clinician-administered or self-reported, is an effective way to moni­tor outcomes, provided the clinician uses the same scales or methods to record a patient’s moods. If a patient wants to dis­continue lithium, taper the drug over an extended period (months) to minimize the likelihood of emerging manic or depressive episodes related to drug discontinuation.

Managing side effects
Consider lithium’s side effects in the con­text of their short-, intermediate-, and long-term presence (Table 2). Gradually increasing the lithium dosage often will prevent side effects that manifest in the short term. If side effects emerge at low dosages, proceed slowly with lithium and manage symptoms with other medica­tions. When a patient shows a change in side effects, obtain lithium and electrolytes levels; a change in mental status with con­fusion will require an acute lithium level.

A diary of symptoms or clinically rel­evant matters such as fluid intake or fre­quency of GI- or neurological-related events will help the clinician monitor the frequency and severity of side effects. The patient and clinician should not be dis­couraged by emerging side effects in the short term, because they may dissipate or become minimally intrusive.

Several strategies can alleviate immedi­ate GI effects, such as dosing with meals, enteric-coated formulations, multiple dose strategies, and short-term use of antidiar­rheal medicine as needed. Side effects that disrupt a patient’s fluid and electrolyte balance (diabetes insipidus) to the point of clouding mental status will require discon­tinuing the medication until mental sta­tus improves, then reconsideration of the treatment regime, which will include man­aging diabetes insipidus with amiloride. Managing side effects may require consulta­tion with specialty services. Likewise, some patients might experience neurologic side effects, such as profound tremor, that inter­feres with their ability to function. However, many side effects can be managed symp­tomatically with practical strategies (eg, a sugar-free lozenge for dry mouth or dysgeu­sia). Consider lower lithium dosages and serum levels because patients may experi­ence benefits with lower therapeutic levels.

Long-term side effects include decreased renal function, hypothyroidism, persistent tremor, and dermatologic effects of acne and alopecia. Monitor renal and thyroid function annually in stable patients and more frequently when making changes in the treatment plan.

Before discontinuing lithium, consider discussing the medical issues with a spe­cialist who has experience with complica­tions of lithium.

Bottom Line
Lithium is an effective and under used medication for managing bipolar disorder. Initial prejudices and side effects often deter patients and prescribers from proceeding with a therapeutic trial of lithium. Although the mid-range lithium level of 0.6 to 0.8 mEq/L is desirable, many patients will experience significant benefits with lower levels. Initial strategies include the use of low-dose preparations that are unlikely to have uncomfortable side effects.

Related Resources
• Andreasen A, Ellingrod VL. Lithium-induced diabetes in­sipidus: prevention and management. Current Psychiatry. 2013;12(7):42-45.
• Cipriani A, Hawton K, Stockton S, et al. Lithium in the pre­vention of suicide in mood disorders: updated system­atic review and meta-analysis. BMJ. 2013;346:f3646. doi: 10.1136/bmj.f3646.

Drug Brand Names
Amiloride • Midamor                Lithium • Eskalith, Lithobid

Disclosure
Dr. McInnis reports no financial relationship with any company whose products are mentioned in this article or with manufacturers of competing products.