Development of a Highly Efficient Extraction Technique and Specific Multiplex Assay for Measuring Antiretroviral Drug Concentrations in Breast MilkRezk, Naser L MS; Abdel-Megeed, Mohamed F PhD; Kashuba, Angela D M PharmDTherapeutic Drug Monitoring: August 2007 - Volume 29 - Issue 4 - p 429-436 doi: 10.1097/FTD.0b013e318074db39 Original Article Abstract Author Information Understanding the pharmacology of drugs in breast milk is important for the health of both mother and baby. Current methods to measure drug concentrations in breast milk are not easily validated for precision or accuracy, primarily because of suboptimal sample clean-up. We report here an optimized clean-up method to remove both proteins and fat from milk, thereby enhancing the extraction efficiency of antiretroviral drugs. Recoveries were consistently above 91% for all drugs, demonstrating that this method successfully and reliably released drugs from fat globules. With use of 200 μL of human breast milk, an high-performance liquid chromatography/ultraviolet method for simultaneously detecting lamivudine, stavudine, zidovudine, and nevirapine was validated over the range of 20 to 20,000 ng/mL. Intra- and interday precision (average percent relative standard deviation) and accuracy (average percent deviation from nominal) was less than 3.6% and 7.5%, respectively. Intra- and interday accuracy (average percent deviation from nominal) was less than 0.25% and 1.3%, respectively. This novel method efficiently, reliably, and accurately measured antiretroviral drugs in breast milk and can be applied to any matrix containing fat and protein. From the Clinical Pharmacology/Analytical Chemistry Core, Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, NC. Received for publication November 22, 2006; accepted April 16, 2007. Sources of Support: The University of North Carolina at Chapel Hill Center for AIDS Research, #9P30 AI50410, and AI54980 (ADMK). Reprints: Naser L. Rezk, MS, 3320 Kerr Hall, CB# 7360, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (e-mail: firstname.lastname@example.org). © 2007 Lippincott Williams & Wilkins, Inc.