1 The concentrations of cyclophosphamide in plasma and saliva were determined in seven patients following administration of single doses of cyclophosphamide during chemotherapy for lymphoma. 2 The saliva/plasma ratio was 0.77 +/‐ 0.24 (s.d.) and showed no time‐ dependence being rapidly established following intravenous and oral administration. 3 The T 1/2 of cyclophosphamide (8.38 +/‐ 2.25 h) determined from salivary measurements was not significantly different from that in plasma (8.24 +/‐ 2.60 h). It was not possible to estimate the apparent volume of distribution or total body clearance utilizing the salivary cyclophosphamide concentration without appropriate correction for the saliva/plasma concentration ratio. 4 The binding to the plasma protein of normal plasma of cyclophosphamide was 13.4 +/‐ 5.3%. The Scatchard plot for binding to bovine serum albumin indicates only weak binding to non‐specific sites. 5 Salivary cyclophosphamide therefore indicates the concentration of the unbound fraction of plasma cyclophosphamide. 1979 The British Pharmacological Society
