title: Thermostability testing and degradation profiles of doxycycline in bulk, tablets, and capsules by HPLC.
abstract: A high-performance liquid chromatography (HPLC) method for the quantitation of doxycycline in bulk, tablets, and capsules after storage at -20, 5, 25, 40, 50, 60, and 70 degrees C, has been developed and validated. The samples are eluted from a micro-Bondapak C8 column (4.6x150-mm, i.d., 5-microm particle size) at 27 degrees C, with a mobile phase of acetonitrile-water-THF (29.5:70:0.5, v/v/v), adjusted to pH 2.5 with 1.0M HCl. The flow rate is 1.0 mL/min and detection by UV is at 350 nm. The stability of doxycycline in bulk and in pharmaceuticals is checked over 90 days. Doxycycline shows thermo-degradation after exposure to high temperature; tablets are more stable than capsules. The shelf lives (t90%) are determined to be 1.00, 2.84, and 5.26 years in bulk, capsules, and tablets, respectively, at 25 degrees C. Metacycline and 6-epidoxycyline are identified as degradation products at high temperatures. Amounts of doxycycline, metacycline, and 6-epidoxycycline in all samples are determined by HPLC, and the results compare with those from micellar electrokinetic capillary chromatography. After 90 days, metacycline and 6-epidoxycyline are almost equal in test samples from standard bulk form, tablets, and capsules. It is 27.8+/-0.3%, 13.7+/-0.1%, and 18.8+/-0.2%, respectively.
authors.affiliation: Faculty of Pharmacy, Department of Pharmaceutical Biology, University of Ljubljana, Askerceva 7, 1000 Ljubljana, Slovenia. injacrade@gmail.com
authors.forename: Rade
authors.initials: R
authors.lastname: Injac
authors.forename: Vukosava
authors.initials: V
authors.lastname: Djordjevic-Milic
authors.forename: Branislava
authors.initials: B
authors.lastname: Srdjenovic
mesh_terms: D002214:Capsules / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D020374:Chromatography, Micellar Electrokinetic Capillary; D004318:Doxycycline / Q000737:chemistry*; D004355:Drug Stability; D006358:Hot Temperature; D013607:Tablets / Q000032:analysis
chemical_list: D002214:Capsules; D013607:Tablets; D004318:Doxycycline