Lithium has been a staple treatment for bipolar disorder for ages. Ancient Romans and Greeks used water containing lithium as a treatment for “agitated and euphoric” patients. Lithium was re-introduced with modern psychiatry in the 1970’s to treat what was then called “manic depression” and is still the first-line treatment recommended by the U.S. Department of Health & Human Services. Despite this recommendation and its proven efficacy, only 20-35% of bipolar patients take lithium on a regular basis. One reason for this is the risk of lithium toxicity.
Lithium is highly effective in treating manic episodes as well as its use as maintenance therapy. About 75% of patients who are prescribed lithium see at least some improvement in symptom severity. There are other benefits including its ability to protect brain from neurodegenerative disorders and increasing the volume of areas of the brain that tend to be smaller in those affected by bipolar disorder.
So why aren’t more patients taking it? There are a couple of reasons.
1 Side effects
All bipolar disorder medications come with side effects like weight gain, sexual dysfunction and drowsiness. However, lithium also carries an increased risk for kidney damage (both acute and chronic) and hypothyroidism. The damage to the kidneys and thyroid can either be temporary or permanent, but the odds of permanent damage increase with the length of time lithium is used.
2 It requires consistent monitoring
Most bipolar disorder medication dosages are determined by treatment effectiveness alone. For example, if a person is taking a mood stabilizer like lamotrigine and they don’t feel much improvement, their psychiatrist may increase the dose and ask to see them in a month to see if symptoms have improved. With lithium, that’s not the case. Patients also have to endure blood tests to monitor its concentration in the blood stream. Blood tests are done five days after a dosage change and every 3-6 months thereafter. Bipolar disorder patients are notorious for not adhering to medication, so adding the need for laboratory testing can increase the odds of treatment noncompliance.
Lithium is prescribed at the absolute minimum dose that proves effective. One of the reasons behind this is the aforementioned risk of kidney or thyroid damage. Another is the risk of developing lithium toxicity.
There are two types of lithium toxicity- acute and chronic. Acute toxicity happens when too much medication is taken at one time (an overdose). Chronic toxicity takes place when the blood serum level of lithium is too high for an extended period of time. To add another complication, blood serum levels are not just determined by the medication dosage. Hormone levels, illness, season changes and other medications can all alter blood serum levels. Fortunately, both types of toxicity have recognizable symptoms, though they can still be mild, even with severe overdose.
Acute Lithium Toxicity
- Blurred vision
- Poor motor coordination
- Muscle aches
Chronic Lithium Toxicity
- Any of the acute toxicity symptoms
- Slurred speech
- Memory problems
- Frequent urination
- Electrolyte imbalance/low blood sodium
Optimal levels of lithium in blood serum is 0.6-1.2mEq/L. Symptoms of toxicity typically show up around serum levels of 1.5mEq/L. Cases of severe lithium toxicity are rare, occurring in only around 7% of patients. When they do occur, treatments like infused saline solution or hemodialysis are used with high success rates.
While lithium toxicity is a concern with taking the drug to treat bipolar disorder, it is overall safe and effective. For most patients, the benefits out way the costs. All the same, it is important for psychiatrists and patients to discuss the risks of toxicity and the side effects of lithium treatment, just as they should with any other treatment.
Image credit: Martin Walker