Lithium is a drug used as an antipsychotic in the treatment of bipolar disorder. Occasionally, it can be used in other disorders to augment an antidepressant that does not adequately treat a depression. This test measures the amount of lithium in the blood.
Bipolar disorder is a mental condition characterized by alternating periods of depression and mania. These periods may be as short as a few days or weeks or as long as months or years. During a depressive episode, those affected may feel sad, hopeless, worthless, and lose interest in daily activities. They may be fatigued but have trouble sleeping, experience weight loss or gain, have difficulty concentrating, and have thoughts of suicide. During a manic episode, those affected may be euphoric, irritable, have high energy and grandiose ideas, use poor judgment, and participate in risky behaviors. Sometimes affected people will have mixed episodes with aspects of both mania and depression. Bipolar disorder can affect both adults and children.
Lithium is prescribed to stabilize the mood swings of a person with bipolar disorder. It is often called a "mood stabilizer" and is sometimes prescribed for people with depression who are not responding well to other medications. Less commonly, lithium may be prescribed to prevent schizoaffective disorder and cluster headaches.
Because lithium is a relatively slow-acting drug, its effect on mood may take several weeks. Dosages of the drug are adjusted until blood concentrations are within a therapeutic range—the blood level range that achieves the desired effect and treats an individual's bipolar disorder. The actual amount of drug that it will take to reach this steady state will vary from person to person and may be affected by a person's age, general state of health, and other medications that they are taking.
Lithium levels are monitored on a regular basis because blood levels must be maintained within a narrow therapeutic range. Too little and the medication will not be effective; too much and symptoms associated with lithium toxicity may develop.
Types of Toxicity
There are three types of lithium toxicity: acute, chronic, and acute-on-chronic.
Acute lithium toxicity occurs when someone who isn't taking lithium at all ingests it. This could happen when a family member takes pills from the wrong bottle, when a child gets into a parent's medications, or in a suicide attempt by someone who doesn't use lithium.
Acute toxicity can carry somewhat less medical risk and less severe symptoms than the other types, depending on the amount taken, because lithium will clear out of your body more quickly when your system is unused to it.
The chronic form of lithium toxicity can occur when you take lithium daily but your serum blood level has crept up into the toxic range. Possible causes for this level increase are a dosage increase, being dehydrated, interactions with other medications, and problems with kidney function.
This type of toxicity is less likely to be detected early than the other types, so more severe symptoms may appear before it's identified. Medications that can contribute to dehydration or cause your kidneys not to function as well as normal include diuretics, angiotensin-converting enzyme (ACE) inhibitors, and nonsteroidal anti-inflammatory drugs (NSAIDs).
When you regularly take lithium and you accidentally or deliberately take a higher dose than prescribed, this results in acute-on-chronic toxicity. Because the levels in your blood that make lithium effective and the levels that make it toxic are so close, the additional amount that causes acute-on-chronic toxicity doesn't have to be terribly high. This type of lithium toxicity is considered to be the most severe form, with the highest potential for long-term consequences.
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