Determination of methylprednisolone in central nervous tissue and plasma using normal-phase high-performance liquid chromatography

A sensitive and specific high-performance liquid chromatographic technique is described for the quantitative measurement of the synthetic glucocorticoid methylprednisolone in central nervous tissue (spinal cord) and plasma. Following intravenous administration, methylprednisolone is extracted from spinal cord tissue with diethyl ether-methylene chloride (60:40, v/v). The extract is washed sequentially with alkali, acid and water, concentrated, then chromatographed on an NH₂ column using a mobile phase of methylene chloride-isopropanol (85:15, v/v). Steroid elution is monitored with an ultraviolet detector set at 254 nm. Such a system has a detection limit of 2.8 ng methylprednisolone. Extraction of methylprednisolone from spinal cord tissue is linear with tissue concentration and the recovery is around 70%. Endogenous hydrocortisone or other metabolites in the tissue do not interfere with the methylprednisolone peak. A description of the quantitation of methylprednisolone in cat lumbar spinal cord and plasma samples after single intravenous doses of methylprednisolone sodium succinate is given.