Optimized HPLC method for tramadol and O-desmethyl tramadol determination in human plasma

Area of Science:

• Analytical Chemistry
• Pharmacology

Background:

• Accurate quantification of tramadol and its metabolite O-desmethyl tramadol in human plasma is crucial for therapeutic drug monitoring.
• Existing methods may require optimization for improved sensitivity and efficiency.

Purpose of the Study:

• To develop and validate a novel, optimized High-Performance Liquid Chromatography (HPLC) method for determining tramadol and O-desmethyl tramadol concentrations in human plasma.
• To establish the method's reliability, sensitivity, and stability for clinical use.

Main Methods:

• Liquid-liquid extraction of analytes from plasma using ethyl acetate.
• HPLC separation on a RP-18 column with a C18 precolumn under gradient elution at 15°C.
• Fluorescence detection with optimized excitation/emission wavelengths.
• Validation using sotalol as an internal standard, assessing intra-day and between-days variability and bias.

Main Results:

• The method achieved low limits of quantification (LLOQ): 4.078 ng/ml for tramadol and 3.271 ng/ml for O-desmethyl tramadol.
• High precision and accuracy were demonstrated, with coefficients of variation (CV%) and bias% within acceptable ranges for both intra-day and between-days assays.
• Tramadol and O-desmethyl tramadol were found to be stable in plasma for four weeks at -20°C and in the re-eluted solution for 48 hours at 15°C.

Conclusions:

• The developed HPLC method is sensitive, accurate, and robust for quantifying tramadol and O-desmethyl tramadol in human plasma.
• The method's validated stability characteristics support its use in pharmacokinetic studies and clinical settings.
• This optimized approach provides a reliable tool for monitoring tramadol therapy and understanding its metabolic profile.