Lithium
For a more detailed discussion of this topic, see Lithium, Sec. 31.19, p. 3132, in Comprehensive Textbook of Psychiatry, 9th Edition.
The effectiveness of lithium for mania and for the prophylactic treatment of manic-depressive disorder was established in the early 1950s, largely as a result of research done by John F.J. Cade, an Australian psychiatrist. Concerns about toxicity limited initial acceptance of lithium use in the United States, but its use increased gradually in the late 1960s. It was not until 1970 that the U.S. Food and Drug Administration (FDA) approved its labeling for the treatment of mania. The only other approved FDA indication came in 1974 when it was accepted as maintenance therapy in patients with a history of mania. For several decades, lithium was the only drug approved for both acute and maintenance treatment. It is also used as an adjunctive medication in the treatment of major depressive disorder.
Lithium (Li), a monovalent ion, is a member of the group IA alkaline metals on the periodic table, a group that also includes sodium, potassium, rubidium, cesium, and francium. Lithium exists in nature as both 6Li (7.42%) and 7Li (92.58%). The latter isotope allows the imaging of lithium by magnetic resonance spectroscopy. Some 300 mg of lithium is contained in 1,597 mg of lithium carbonate (Li2CO3). Most lithium used in the United States is obtained from dry lake mining in Chile and Argentina.
Pharmacologic Actions
Lithium is rapidly and completely absorbed after oral administration, with peak serum concentrations occurring in 1 to 1.5 hours with standard preparations and in 4 to 4.5 hours with slow- and controlled-released preparations. Lithium does not bind to plasma proteins, is not metabolized, and is excreted through the kidneys. The plasma half-life is initially 1.3 days and is 2.4 days after administration for more than 1 year. The blood–brain barrier permits only slow passage of lithium, which is why a single overdose does not necessarily cause toxicity and why long-term lithium intoxication is slow to resolve. The elimination half-life of lithium is 18 to 24 hours in young adults but is shorter in children and longer in elderly persons. Renal clearance of lithium is decreased with renal insufficiency. Equilibrium is reached after 5 to 7 days of regular intake. Obesity is associated with higher rates of lithium clearance. The excretion of lithium is complex during pregnancy; excretion increases during pregnancy but decreases after delivery. Lithium is excreted in breast milk and in insignificant amounts in the feces and sweat. Thyroid and renal concentrations of lithium are higher than serum levels.
An explanation for the mood-stabilizing effects of lithium remains elusive. Theories include alterations of ion transport and effects on neurotransmitters and neuropeptides, signal transduction pathways, and second messenger systems.
Therapeutic Indications
Bipolar I Disorder
Manic Episodes
Lithium controls acute mania and prevents relapse in about 80% of persons with bipolar I disorder and in a somewhat smaller percentage of persons with mixed (mania and depression) episodes, rapid-cycling bipolar disorder, or mood changes in encephalopathy. Lithium has a relatively slow onset of action when used and exerts its antimanic effects over 1 to 3 weeks. Thus, a benzodiazepine, dopamine receptor antagonist (DRA), serotonin–dopamine antagonist (SDA), or valproic acid is usually administered for the first few weeks. Patients with mixed or dysphoric mania, rapid cycling, comorbid substance abuse, or organicity respond less well to lithium than those with classic mania.
Bipolar Depression
Lithium has been shown to be effective in the treatment of depression associated with bipolar I disorder, as well as in the role of add-on therapy for patients with severe major depressive disorder. Augmentation of lithium therapy with valproate (Depakene) or carbamazepine (Tegretol) is usually well tolerated, with little risk of precipitation of mania.
When a depressive episode occurs in a person taking maintenance lithium, the differential diagnosis should include lithium-induced hypothyroidism, substance abuse, and lack of compliance with the lithium therapy. Possible treatment approaches include increasing the lithium concentration (up to 1 to 1.2 mEq/L), adding supplemental thyroid hormone (e.g., 25 µg a day of liothyronine [Cytomel]) even in the presence of normal findings on thyroid function tests, augmentation with valproate or carbamazepine, the judicious use of antidepressants, or electroconvulsive therapy (ECT). After the acute depressive episode resolves, other therapies should be tapered off in favor of lithium monotherapy, if clinically tolerated.
Maintenance
Maintenance treatment with lithium markedly decreases the frequency, severity, and duration of manic and depressive episodes in persons with bipolar I disorder. Lithium provides relatively more effective prophylaxis for mania than for depression, and supplemental antidepressant strategies may be necessary either intermittently or continuously. Lithium maintenance is almost always indicated after the first episode of bipolar I disorder depression or mania and should be considered after the first episode for adolescents or for persons who have a family history of bipolar I disorder. Others who benefit from lithium maintenance are those who have poor support systems, had no precipitating factors for the first episode, have a high suicide risk, had a sudden onset of the first episode, or had a first episode of mania. Clinical studies have shown that lithium reduces the incidence of suicide in bipolar I disorder patients six- or sevenfold. Lithium is also effective treatment for persons with severe cyclothymic disorder.
Initiating maintenance therapy after the first manic episode is considered a wise approach based on several observations. First, each episode of mania increases the risk of subsequent episodes. Second, among people responsive to lithium, relapses are 28 times more likely after lithium use is discontinued. Third, case reports describe persons who initially responded to lithium, discontinued taking it, and then had
a relapse but no longer responded to lithium in subsequent episodes. Continued maintenance treatment with lithium is often associated with increasing efficacy and reduced mortality. Therefore, an episode of depression or mania that occurs after a relatively short time of lithium maintenance does not necessarily represent treatment failure. However, lithium treatment alone may begin to lose its effectiveness after several years of successful use. If this occurs, then supplemental treatment with carbamazepine or valproate may be useful.
a relapse but no longer responded to lithium in subsequent episodes. Continued maintenance treatment with lithium is often associated with increasing efficacy and reduced mortality. Therefore, an episode of depression or mania that occurs after a relatively short time of lithium maintenance does not necessarily represent treatment failure. However, lithium treatment alone may begin to lose its effectiveness after several years of successful use. If this occurs, then supplemental treatment with carbamazepine or valproate may be useful.
Maintenance lithium dosages can often be adjusted to achieve plasma concentration somewhat lower than that needed for treatment of acute mania. If lithium use is to be discontinued, then the dosage should be slowly tapered. Abrupt discontinuation of lithium therapy is associated with an increased risk of recurrence of manic and depressive episodes.
Major Depressive Disorder
Lithium is effective in the long-term treatment of major depression but is not more effective than antidepressant drugs. The most common role for lithium in major depressive disorder is as an adjuvant to antidepressant use in persons who have failed to respond to the antidepressants alone. About 50 to 60% of antidepressant nonresponders do respond when lithium, 300 mg three times daily, is added to the antidepressant regimen. In some cases, a response may be seen within days, but most often, several weeks are required to see the efficacy of the regimen. Lithium alone may effectively treat depressed persons who have bipolar I disorder but have not yet had their first manic episode. Lithium has been reported to be effective in persons with major depressive disorder whose disorder has a particularly marked cyclicity.
Schizoaffective Disorder and Schizophrenia
Persons with prominent mood symptoms—either bipolar type or depressive type—with schizoaffective disorder are more likely to respond to lithium than are those with predominant psychotic symptoms. Although SDAs and DRAs are the treatments of choice for persons with schizoaffective disorder, lithium is a useful augmentation agent. This is particularly true for persons whose symptoms are resistant to treatment with SDAs and DRAs. Lithium augmentation of an SDA or DRA treatment may be an effective treatment for persons with schizoaffective disorder even in the absence of a prominent mood disorder component. Some persons with schizophrenia who cannot take antipsychotic drugs may benefit from lithium treatment alone.
Other Indications
Over the years, reports have appeared about the use of lithium to treat a wide range of other psychiatric and nonpsychiatric conditions (Tables 18-1 and 18-2). The
effectiveness and safety of lithium for most of these disorders have not been confirmed. Lithium has antiaggressive activity that is separate from its effects on mood. Aggressive outbursts in persons with schizophrenia, violent prison inmates, and children with conduct disorder and aggression or self-mutilation in persons with mental retardation can sometimes be controlled with lithium.
effectiveness and safety of lithium for most of these disorders have not been confirmed. Lithium has antiaggressive activity that is separate from its effects on mood. Aggressive outbursts in persons with schizophrenia, violent prison inmates, and children with conduct disorder and aggression or self-mutilation in persons with mental retardation can sometimes be controlled with lithium.
Table 18-1 Psychiatric Uses of Lithium | ||
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Table 18-2 Nonpsychiatric Uses of Lithiuma | ||
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Precautions and Adverse Effects
More than 80% of patients taking lithium experience side effects. It is important to minimize the risk of adverse events through monitoring of lithium blood levels and to use appropriate pharmacologic interventions to counteract unwanted effects when
they occur. The most common adverse effects are summarized in Table 18-3
they occur. The most common adverse effects are summarized in Table 18-3
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