Doxycycline binding to plasma albumin of several species

The affinity of doxycycline for crystalline plasma albumin fraction V, originating from sheep, dogs, cats, cows, pigs and humans, was evaluated by means of double-reciprocal and Scatchard plots. Mathematical modelling and weighted least-squares non-linear regression analysis of each Scatchard plot identified one binding component characterized by one high affinity binding site, and a second component attributed to non-specific binding to albumin. Association constants for this binding site ranged from 38,471 +/- 13,369 (SEM) l/mol for the interaction of doxycycline with ovine albumin to 6405 +/- 2375 l/mol for the interaction of doxycycline with human albumin. Statistical evaluation of the results suggested slight species-related differences in the values of association constants. Diphenylhydantoin, phenobarbital or carbamazepine did not displace doxycycline from binding sites on bovine albumin.