Measurement of platinum in saliva of patients treated with cisplatin.

A procedure for the measurement of platinum (Pt) in the saliva of patients treated with cisplatin has been developed. The saliva is collected and solubilized in hyamine hydroxide before analysis by graphite furnace atomic absorption spectrometry using assay by standard additions. The method has an analytical detection limit of 0.025 microgram/mL and is precise, with coefficients of variation of 3-10.0% over a range of 0.05-2.0 micrograms/mL. Platinum was measured in saliva collected during an 8-h infusion of cisplatin from five patients, at the end of a 30-min infusion in nine, and 24 and 48 h later from a further 15 patients, all of whom were treated with cisplatin for squamous cell carcinoma of the neck. The platinum concentration in saliva taken at the end of a 30-min infusion was 0.27 +/- 0.23 microgram/mL (mean +/- 1 SD) but was below the detection limit of 0.025 microgram/mL at 24 and 48 h. After an 8-h infusion the salivary Pt was significantly less (0.12 +/- 0.04 microgram/mL; P < 0.05). The plasma Pt concentrations after 30-min and 8-h infusions were 2.98 +/- 1.03 and 2.54 +/- 0.59 micrograms/mL, respectively, and were not significantly different. The results indicate higher concentrations of free platinum in plasma after 30 min compared with an 8-h infusion. The monitoring of salivary concentrations of platinum may therefore provide a non-invasive way to study the unbound fraction of cisplatin in blood and facilitate optimization of cisplatin treatment.