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A Sensitive and Simple High
Performance Liquid
Chromatographic Method for
Quantification of Tadalafil in
Human Serum
Bioequivalence and Quality Control Laboratory, Faculty of Pharmacy, Saint-Joseph University,Mathaf, Lebanon KEY WORDS: HPLC, tadalafil, assay,
centration range tested (10-800 ng/mL).
Accuracy, precision, and stability studieswere satisfactory. This analytical proce- ABSTRACT
dure is relatively inexpensive and simple paraben was used as the internal stan-dard. Optimum conditions for tadalafil INTRODUCTION
Tadalafil is a potent and selective phos- single-step liquid–liquid extraction with vasodilation of erectile tissues.1-3 Oral less than 10 ng/mL for tadalafil. The cali- The Journal of Applied Research • Vol. 6, No. 1, 2006 Table 1. Intraday Variability of the Assay for Tadalafil in Serum (4 series) Concentration
Concentration
Standard
Coefficient
Added (ng/mL)
Found (ng/mL)
Deviation
of Variation (%)
Correlation coefficients are 0.9984, 0.9984, 0.9984, and 0.9993 for each of the 4 curves.
Table 2. Interday Variability of the Assay for Tadalafil in Serum (5 series) Concentration
Concentration
Standard
Coefficient
Added (ng/mL)
Found (ng/ml)
Deviation
of Variation (%)
Correlation coefficients are 0.9993, 0.9993, 0.9991, 0.9993, and 0.9993 for each of the 5 curves oral dosing has not been determined.
life of 17.5 hours in healthy subjects.5-7 Lebanon, and is described in this report.
be determined in biological samples,dietary supplements, or herbal matrices EXPERIMENT
Reagents and Standards
All chemicals used were reagent grade.
tion8-10 or micellar electrokinetic capil- The Journal of Applied Research • Vol. 6, No. 2, 2006 Figure 1. Chromatograms of (A) standard tadalafil solution, (B) extracted sample at 800 ng/mL, (C) blank serum, (D) blank serum with internal standard, and (E) extracted sample at 10 ng/mL. Station, NJ). Tadalafil standard was sup- water/acetonitrile (50/50, v/v). Internal Vol. 6, No. 2, 2006 • The Journal of Applied Research Table 3. Tadalafil Recovery After Extraction: Tadalafil at Different Concentrations and USA). The data were collected using thesystem software (Chemstation 1990- Concentration
Average Extraction
Coefficient (%)
(n=3 for each level)
Chromatographic Conditions
5-µm particle size, 250 x 4 mm I.D., with with glacial acetic acid (0.1 mM, pH 2.5- UV detection was performed at 280 nm.
All analyses were made at room temper-ature. The injection volume was 25 µL, trile. All stock solutions were protected through each sample before injection.
from light and kept at -20˚C. They werestable for at least 6 months.
Serum Extraction Procedure
stock solution with drug-free serum.
Stability of the drug in serum at –20˚C a micropipette while gently vortexingthe tubes. To each tube 6 cc of Instrumentation
Table 4. Drug-Free Human Serum Spiked With 3 Different Concentrations of Tadalafil and Stored at
–20˚C Over a 6-Month Period
Concentration
Concentration Obtained (ng/mL)
The Journal of Applied Research • Vol. 6, No. 2, 2006 dichloromethane extraction of serumsamples were not less than 75% over the Assay Validation
For assay validation, tadalafil was mixedwith drug-free human serum over the Stability
stored at –20˚C did not show significant ined using 4 series, and interday variabil- performed on 5 separate days. Tables 1and 2 show the results of within-run and DISCUSSION AND CONCLUSION
described in this report for the determi- studied (correlation coefficients 0.998 to ng/mL were not tested for linearity.
ric detection is not available. The assay tetraacetic acid in the collection tube.
for determination of tadalafil concentra- than 10 ng/mL showed CVs more than10% and were not incorporated in the REFERENCES
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Seftel AD. Phosphodiesterase type 5 inhibitor Extraction Yield
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inhibitors for erectile dysfunction. J Clin 10. Zhu X, Xiao S, Chen B, et al. Simultaneous determination of sildenafil, vardenafil and tadalafil as forbidden components in natural dietary supplements for male sexual potency treatment of erectile dysfunction. Expert by high-performance liquid chromatography- Opin Pharmacother. 2003;4:2049-2056.
electrospray ionization mass spectrometry. J Chromatogr A. 2005;1066:89-95.
phosphodiesterase-5 inhibitors. Int J Clin 11. Rodriguez Flores J, Berzas Nevado JJ, Development of a micellar electrokinetic cap- et al. Quantification of tadalafil in human illary chromatography method for the deter- mass spectrometry with electrospray ioniza- erectile dysfunction therapy. J Chromatogr B tion. J Chromatogr B Analyt Technol Biomed The Journal of Applied Research • Vol. 6, No. 2, 2006

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