Method development and validation of liquid chromatography-tandem/mass spectrometry for aldosterone in human plasma: Application to drug interaction study of atorvastatin and olmesartan combination

In the present investigation, a simple and sensitive liquid chromatography-tandem mass spectrometry (LC/MS/MS) method was developed for the quantification of aldosterone (ALD) a hormone responsible for blood pressure in human plasma. The developed method was validated and extended for application on human subjects to study drug interaction of atorvastatin (ATSV) and olmesartan (OLM) on levels of ALD. The ALD in plasma was extracted by liquid-liquid extraction with 5 mL dichloromethane/ethyl ether (60/40% v/v). The chromatographic separation of ALD was carried on Xterra, RP-Column C18 (150 mm× 4.6 mm × 3.5 μm) at 30°C followed by four-step gradient program composed of methanol and water. Step 1 started with 35% methanol for first 1 min and changed linearly to 90% in next 1.5 min in Step 2. Step 3 lasted for next 2 min with 90% methanol. The method finally concluded with Step 4 to achieve initial concentration of methanol that is, 35% thus contributing the total method run time of 17.5 min. The flow rate was 0.25 mL/min throughout the process. The developed method was validated for specificity, accuracy, precision, stability, linearity, sensitivity, and recovery. The method was linear and found to be acceptable over the range of 50-800 ng/mL. The method was successfully applied for the drug interaction study of ATSV + OLM in combination against OLM treatment on blood pressure by quantifying changes in levels of ALD in hypertensive patients. The study revealed levels of ALD were significantly higher in ATSV + OLM treatment condition when compared to OLM as single treated condition. This reflects the reason of low effectiveness of ATSV + OLM in combination instead of synergistic activity.