Lithium (Eskalith, Lithobid)
A drug used in the form of its salts for the prevention and treatment of manic-depressive illness (bipolar depression) and in the prevention of recurrent depression (unipolar depression). Its mechanism of action is unclear, but it inhibits the action of an important enzyme involved in the transmission of signals in the brain. Lithium may be added to tricyclic antidepressants to increase their effectiveness. The concentrations of lithium in the blood that are therapeutically effective may be close to those that produce toxic effects. Plasma concentrations of lithium should therefore be monitored carefully and the dosage adjusted as necessary. Overdosage can be fatal. Lithium is available as lithium carbonate and lithium citrate.
Different products have different absorption characteristics, therefore it is not advisable to change brands of medication unless specifically instructed to do so
Side effects: these are dose-related and develop as concentrations of lithium in the blood increase. They include nausea, vomiting, and diarrhoea, fine tremor, increased urine production, weight gain, and oedema. Signs of lithium intoxication include blurred vision, increasing gastrointestinal disturbances, drowsiness and lethargy, giddiness, coarse tremor, and lack of coordination. Treatment may need to be stopped.
Precautions: lithium salts should not be used to treat children, people with kidney or heart disease, or those with sodium imbalance (lithium toxicity is exacerbated by sodium depletion). They should be used with caution in elderly people and in women who are pregnant or breastfeeding.
Interactions with other drugs: lithium interacts with a wide variety of drugs including:
ACE inhibitors: increase concentrations of lithium in the blood.
Antibiotics: metronidazole and spectinomycin increase concentrations of lithium in the blood.
Anticonvulsants: carbamazepine and phenytoin may increase lithium
toxicity without increasing plasma concentrations of lithium.
Antiemetics: there is an increased risk of *extrapyramidal reactions with
domperidone and metoclopramide. Calcium antagonists: diltiazem and verapamil may increase lithium
toxicity without increasing plasma concentrations of lithium.
Diuretics: increase concentrations of lithium in the blood. As lithium toxicity is exacerbated
by sodium depletion, the use of diuretics, especially thiazides, with lithium is hazardous. Haloperidol: increases concentrations of lithium in the blood.
Methyldopa: may increase toxicity of lithium without increasing plasma
lithium concentrations.
NSAIDs: increase concentrations of lithium in the blood and their use
with lithium should be avoided.
SSBls: increase concentrations of lithium in the blood. Sumatriptan: increases the adverse effects of lithium on the nervous
system. Theophylline: may reduce concentrations of lithium in the blood.