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Question:

My sister-in-law, 48, has serious, chronic mental illness and lives in a transitional home for psychiatric patients. Recently, she was sent to the ICU because of toxic levels of lithium in her system. How can this crisis occur in a transitional home?

Answered by: David Kahn

Lithium toxicity occurs when the blood level of lithium rises too high, and begins to cause symptoms of brain malfunction.

Therapeutic blood levels of lithium are usually in the range of 0.6-1.0 milliequivalents per liter (mEq/L). Early signs of toxicity such as increasing tremor and nausea can occur at levels of 1.2-1.5 mEq/L, and more severe signs progessing to severe confusion, seizures and coma can develop at levels over 2 mEq/L. These numbers are not hard and fast, and some people show toxicity at levels below 1 mEq/L, while others show no signs at levels of 1.5 - so paying attention to changing side effects, as well as regularly monitoring blood levels, is very important.

Toxicity usually occurs due to metabolic changes, or more rarely, if someone takes extra lithium beyond what was prescribed.

There are several types of metabolic changes that can lead to toxicity. Lithium is excreted from the body through the kidneys. It is filtered out in the urine, carried out with other wastes. A person can begin to retain excessive amounts of lithium for three reasons: 1) dehydration (not enough water in the body); 2) decreased kidney function, so that the filtering mechanism doesn't work well enough; or 3) interactions with other medications.

The first cause, dehydration, can result from fluid loss (for example, loss due to diarrhea, vomiting, gastroenteritis, high fever, having a bad cold, very hot weather, etc.) or not eating and drinking enough (for example, becoming depressed and loseing one's appetite). If any of these conditions develop in a person taking lithium, it is important to increase fluid intake, increase the intake of table salt by sprinkling it on foods to help the body hold on to more water, and often temporarily reduce or hold the dose of lithium under a doctor's direction. Dehydration can occur suddenly, so it is important to be aware of these factors and check with a doctor quickly if any of them develop.

The second cause, decreased kidney function, happens either with aging, or with disease such as hypertension or diabetes that can impair the kidneys. Periodic monitoring of blood tests for lithium levels and kidney function, as well as urine tests every six months or so can detect these types of changes, and lead to an adjustment in lithium dosage over time.

The third cause, drug interactions, happens with other medicines that either cause dehydration or change the function of the kidneys. Such drugs include commonly used blood pressure medications, such as diuretics, as well as many non-steroidal anti-inflammatory drugs used for arthritis or headaches, such as ibuprofen. Poeple taking lithium should discuss this with their doctor before starting a new medication.

Apart from metabolic problems, toxicity can also occur from taking too much lithium, either in a suicide attempt or by mistake, for example, not being sure if someone took the medication the night before and trying to catch up with extra medicine. From your question, it sounds like neither of these was the situation, but I mention them because they must be considered as well.

For treating mild toxicity, oral fluids and salt are often sufficient, along with holding the lithium until the blood level falls. Intravenous fluid and sometimes temporary kidney dialysis are needed in severe cases of lithium toxicity. The situation can take a few days to reverse in the ICU.

I hope that your sister recuperated fully and is feeling well again, and that an explanation was found to prevent this from happening again.