Comparison of plasma and saliva levels of metoprolol and oxprenolol.

1 Plasma and saliva levels of metoprolol and oxprenolol have been compared in two groups of healthy volunteers. 2 Mean salivary oxprenolol levels were lower than, but closely related to the corresponding plasma levels (r=0.93), the mean ratio of saliva:plasma concentration being 0.42. 3 Mean salivary metoprolol concentrations were considerably greater thatn the corresponding plasma levels and the relationship between the concentrations in the two fluids was less clear. 4 The evidence presented suggests that oxprenolol diffuses passively whilst metoprolol is actively secreted into saliva. The mechanism involved in the active process is not known.