For those diagnosed with a mental illness or disorder, one of the most effective medications used for treatment is lithium. It is particularly useful when treating conditions such as bipolar disorder. It controls moods effectively, keeps people stable and active, and generally allows for a good quality of life. Over time, however, lithium can also create an unwanted side effect: diabetes insipidus.
Lithium induced diabetes insipidus will typically first be discovered on a routine checkup or walk-in appointment, either at the doctor’s office or with the individual’s psychiatrist. The most common complaint is an increased level of thirst, but there may also be unusual daytime fatigue, problems sleeping at night, and even muscle tremors.
Why Does Lithium Cause Diabetes Insipidus?
Medical science doesn’t actually know why lithium will sometimes cause diabetes insipidus to form. What is known is that lithium works in some way as a counter-agent to the hormone Vasopressin, which acts as an anti-diuretic hormone [ADH]. When lithium is used for an extended period of time, it will desensitize or reduce the ability of the kidney to respond to the ADH that is being produced by the body.
This means the kidneys stop listening to the hormones, which is a trademark sign of nephrogenic diabetes insipidus. This creates the need to get up frequently at night to go to the bathroom, which creates insomnia and daytime fatigue.
Lithium induced diabetes insipidus is rather common. For those who are receiving long-term lithium therapies, the incidence rate of diabetes insipidus is 40%.
How Is Lithium Induced Diabetes Insipidus Diagnosed?
Upon presentation, the individual with DI will have an interview that examines their entire medical history. If the disease is supsected, then a water restriction test will be conducted. This test is also called a “water fast” and helps to measure how well the body can concentrate urine. If there is a lack of concentration, then a dose of Desmopressin, a synthetic hormone, may be administered to determine if there is a central cause for the diabetes insipidus or if it is related to the lithium.
People who have central diabetes insipidus will see a 50% ore more increase in urine concentration. For those with lithium induced diabetes insipidus, the concentration rates stay below 10%. This test is important because it helps to track the overall severity of the disease.
Can Lithium Induced Diabetes Insipidus Be Reversed?
Lithium induced DI is believed to be dependent on the dose of the medication. In some cases, the symptoms can be reduced or eliminated by using the lowest effective medication dose. If improvements are seen, then function tests will be conducted 2x per year to make sure the lithium regimen is still functioning properly. Lithium saturation tests may be ordered 2x per week during the stabilization period so that issues may be quickly identified.
Sometimes a switch to once-per-day lithium will also provide improvements. This is because it gives the kidneys a longer time of being away from the drug.
Some patients who require the levels of lithium for therapeutic purposes may find relief from their diabetes insipidus through the use of certain diuretics. Amiloride, for example, will help to minimize lithium accumulation throughout the body and may help to make the natural ADH levels more effective. Thiazide diuretics may also be used, but may also require a 50% or greater reduction in lithium medication, so it may not be suitable for everyone.
NSAID medications in combination with diuretics have also been found to be effective in urine concentration increases.
What Is the Outcome of Treatment?
Most lithium induced cases of diabetes insipidus can be resolved and eliminated over time. Whether it is through alternative medications, lower levels of lithium, or through the inclusion of additional diuretics and over the counter medications, the goal of treatment is to continue providing the emotional stability of lithium while eliminating the diabetes insipidus.
For most people with this condition, there is no danger to health. Diabetes insipidus does not damage the kidneys or their ability to filter the blood. It simply creates increased thirst and the need for frequent urination. When these symptoms can be controlled, then lithium therapies can continue on and life can get back to normal.