Lithium carbonate and
lithium citrate are used to prevent ortreat mania. The discovery of lithium
was a milestone in treating mania and bipolar disorders.
When taken orally, lithium is absorbed rapidly and
completely and is distributed to body tissues.
An active drug, lithium isn’t metabolized and is
excreted from the body unchanged.
It’s theorized that in mania, the patient
experiences excessive cat-echolamine stimulation. In bipolar disorder, the
patient is affected by swings between the excessive catecholamine stimulation
of mania and the diminished catecholamine stimulation of depres-sion.
Lithium’s exact mechanism of action is unknown. It
may regulate catecholamine release in the CNS by:
§ increasing norepinephrine and serotonin
§ reducing the release of norepinephrine from
the synaptic vesi-cles (where neurotransmitters are stored) in the presynaptic
§ inhibiting norepinephrine’s action in the
Researchers are also examining lithium’s effects on
electrolyte and ion transport. Lithium may also modify the actions of second
messengers such as cyclic adenosine monophosphate.
Lithium is used primarily to treat acute episodes
of mania and to prevent relapses of bipolar disorders.
Other uses of lithium being researched include
preventing unipo-lar depression and migraine headaches and treating depression,
alcohol dependence, anorexia nervosa, syndrome of inappropriate antidiuretic
hormone, and neutropenia.
Lithium has a narrow therapeutic margin of safety.
A blood level that is even slightly higher than the therapeutic level can be
Serious interactions with other drugs can occur
because of lithi-um’s narrow therapeutic range:
§ The risk of lithium toxicity increases when
lithium is taken with thiazide and loop diuretics and nonsteroidal
§ Administration of lithium with haloperidol,
phenothiazines, or carbamazepine may increase the risk of neurotoxicity.
§ Lithium may increase the hypothyroid effects
of potassium io-dide.
§ Sodium bicarbonate may increase lithium
excretion, reducing its effects.
§ Lithium’s effects are reduced when lithium is
taken with the-ophylline.
A patient on a severe
salt-restricted diet is susceptible to lithium toxicity. On the other hand,an increased intake of
sodium may reduce thetherapeutic effects of lithium. (See Adverse re-actions to lithium.)