An effective method for measuring salivary lithium in patients on anticholinergic drugs.

The parotid salivary response to citric acid and cholinergic agonist and antagonist was assessed in normal volunteers. Gustatory stimulation by circulation of citric acid in the mouth evoked reproducible parotid salivary burst. The salivary response to citric acid was minimally affected by anticholinergic drugs. Analysis of citric acid-evoked parotid saliva revealed a linear relationship between saliva and serum lithium concentrations in affectively ill patients treated with lithium only, or with lithium in combination with anticholinergic drugs. We suggest that parotid saliva lithium levels can be used to guide lithium therapy in patients for whom phlebotomy is not practical.