DEVELOPMENT OF A MULTIANALYTE MASS SPECTROMETRY METHOD FOR QUANTITATION OF ANTIHYPERTENSIVES IN MILK

Abstract

Objective: Hypertension in pregnancy is common and affects about 10% of women. One third of cases persist into the postnatal period requiring treatment with antihypertensive medications to control blood pressure. However, there is a lack of quality evidence to quantify the transfer of antihypertensives into human milk and to therefore recommend their safe use during breastfeeding. Current reviews on this subject are opinion driven or formed upon recommendations from expert working groups based on anecdotal case reports. No antihypertensives are licensed for use during breastfeeding in the UK and many have not been tested during pregnancy or breastfeeding. Design and method: A multi-marker liquid chromatography coupled with triple quadrupole mass spectrometry (LC-MS/MS) assay was developed and optimised to simultaneously quantify 24 antihypertensives and their metabolites (enalapril (and enalaprilat), lisinopril, perindopril, ramipril (and ramiprilat), trandolaprilat, azilsartan, candesartan, irbesartan, olmesartan, telmisartan, valsartan, atenolol, bisoprolol, carvedilol, labetalol, metoprolol, propranolol amlodipine, diltiazem, dehydronifedipine, eplerenone and bumetanide) in milk. Whole, unpasteurised cow's milk was used as surrogate matrix for method development. Analytes were extracted from milk by protein precipitation. Chromatographic analyses were performed on an Agilent Technologies Zorbax Rapid Resolution C18 column using gradient elution. Identification and quantitation were carried out using electrospray ionisation (positive) on an Agilent Technologies 6410 Triple Quad Mass Spectrometer by monitoring specific precursor and fragment ions in multiple reaction monitoring mode using internal standards. The “Standard Practices for Method Validation in Forensic Toxicology” criteria was used for validation. Results: The method passed validation with accuracy (relative error) and precision (coefficient of variation) values were within the pre-defined limits of < or = 15% at all tested concentrations for the analytes. The assay sensitivity of 10ng/ml was sufficient to detect the analytes in milk. Conclusions: To the best of our knowledge, this is the first assay that permits simultaneous quantitation of 24 commonly prescribed antihypertensives and their metabolites from milk to enable safe use in breastfeeding. The results could be used to guide research on which antihypertensives are safe to use whilst breastfeeding and which require an abstinence period prior to continuation of breastfeeding.