Lithium Other names: Lithium salts

Little is known about the way the lithium ion can modify neurotransmission within the CNS. Many of the proposed mechanisms have suggested an inhibitory effect on components of various neurotransmitter signalling pathways, such as cyclic AMP formation, cyclic GMP formation, G-proteins or inositol phosphate metabolism.

Although lithium is a simple ion it can exert a profound effect on both human behaviour and early embryonic development. Manic depressive psychosis, characterised by dramatic savings in mood can be effectively controlled.

Lithium is rapidly and completely absorbed from the gastrointestinal tract when taken in solution as one of its salts.

Peak plasma concentrations are obtained about 0.75 hours after ingestion of lithium. Lithium is reported to have a plasma half life of about 7 to 20 hours during the daytime. Lithium is excreted by the kidneys. There is a narrow margin between the therapeutic and the toxic plasma concentration. Therefore, not only is individual titration of lithium dosage essential to ensure constant plasma concentrations for the patient involved, but the conditions under which the blood samples are taken for monitoring must be carefully controlled. In practice a blood sample drawn 12 hours after the last dose of lithium in a patient who has been taking his daily lithium requirement at the scheduled hours during the past 48 hours is measured. Under such conditions the usual therapeutic plasma concentrations of lithium are 0.6-1.25 mmol/L, with a reported effective range of 0.5-1.5mmol/L.

There is epidemiological evidence that lithium may be harmful to the foetus in human pregnancy. Therefore it is recommended that lithium be discontinued or if the lithium is necessary, the levels in the patient should be monitored closely.

Lithium is a drug on which extensive clinical experience has been obtained.