Discussion
The case presented here taught us two important lessons. First,
relatively low doses of lithium could cause toxicity in patients with
poor general health, such as those suffering from progressive stage
cancer. Second, clinicians often fail to diagnose delirium associated
with lithium poisoning. In this particular case, the general condition
of the patient was poor and fluid intake was reduced, which led to a
decrease in renal function, in turn causing a decrease in excretion. The
end result was the appearance of symptoms of poisoning. In addition, the
patient was in the terminal stages of cancer and had been treated with
anticancer drugs, which may have predisposed her to the observed decline
in renal function. Nevertheless, a daily dose of 300 mg/day is
considered low according to current literature 7,
which underlines the idea that even low doses of the drug could easily
lead to poisoning. Brain metastases, electrolyte abnormalities, and
terminal delirium are the most common causes of psychiatric symptoms in
cancer patients at the terminal stage 9, 10. Taking
the case presented here into account, lithium intoxication should be
considered as a possible diagnosis when myoclonus and gait disturbances
are observed. We should also be aware of the fact that serum lithium
levels often do not correlate with clinical signs 7.
Lithium poisoning should always be considered as a potential cause for
prolonged delirium 7.