Liquid chromatographic estimation of doxycycline in human tissues

A rapid, sensitive and specific liquid chromatographic method is described for the determination of doxycycline in human tissues. The procedure involves mechanical homogenization of tissue samples in hydrochloric acid followed by extraction of the drug and an internal standard into ethyl acetate. Chromatographic separation is performed on a reversed phase column and allows quantitation of tissue levels as low as 0.68 nmol/g using a 200-400 mg sample. Application of the assay to tissue samples obtained from 36 patients confirmed the excellent penetration of doxycycline in organs. The method supersedes the classical microbiological assays in specificity and speed.