Evaluation of solid-phase extraction of basic drugs from human milk.

This article evaluates the use of commercially available cyanopropyl and octadecyl sorbents for the extraction of basic drugs from breast milk. Twenty drugs were selected from different pharmacological groups (beta-blocking agents, antidepressants, anxiolytic sedatives and neuroleptics, antihistamines, alkaloids and an anthelmintic) and subjected to a general solid-phase extraction (SPE) procedure described earlier for plasma samples. This SPE method was developed on a cyanopropyl cartridge and consisted of a conditioning step with methanol and water, the adsorption of the deproteinized matrix, washing with water and/or methanol, and finally the elution of the basic compounds with 0.1% propylamine in methanol. The extracts were further analysed by reversed-phase liquid chromatography (RP-LC). The application of SPE to human milk samples utilized cyanopropyl and octadecyl cartridges. The latter can be applied more generally because it better retains the basic compounds. For 14 out of 17 drugs extracted from breast milk, recoveries of greater than 70% were obtained. Standard deviations were, with the exception of three drugs, in the same range as those observed for plasma samples, i.e. 2-8%. The development of a strategy for SPE of drugs from human milk was difficult. For a number of drugs, in particular those present in human milk at low concentrations and/or detected in a non-selective way, matrix compounds interfered with the subsequent LC analysis. Therefore, SPE on CN or C18-sorbent for the analysis of basic compounds in breast milk was found to be useful as one of the steps in an extraction procedure, but not as a single technique. A major drawback of SPE is the batch-to-batch variation of the sorbents.