Simple and reliable method of doxycycline determination in human plasma and biological tissues

Over recent years there has been a resurgence in the use of doxycycline in clinical practice, which does not depend on its antibacterial properties. T his paper describes a method of determination of doxycycline in human plasm a and atheromatous tissue using high-performance liquid chromatography (HPL C), and a cheap commercially available extraction system. Doxycycline is ex tracted in the mobile phase and injected directly into the HPLC system, avo iding time consuming drying up steps. A limit of detection of 0.125 mu g/ml of plasma, and a relative standard deviation of 3% was achieved, making th e method very reliable and useful for assays within the usual therapeutic r ange. The method has also been applied to the extraction of a mixture of te tracyclines from plasma and atherma with equal efficacy, making it useful f or assays of this class of drugs in veterinary practice and assays of food contaminants. (C) 2000 Elsevier Science B.V. All rights reserved.