QUANTIFICATION OF OXYTOCIN IN PHARMACEUTICAL DOSAGE FORMS AVAILABLE IN DRUG MARKET OF IRAN BY USING HIGH PERFORMANCE LIQUID CHROMATOGRAPHY METHOD (HPLC)

Quality control of medicinal products- especially the amount of active
ingredients of toxic side effects and complications- is important. The present study was performed to
measure oxytocin (OT) in commercially available drug products in the drug market of Iran.
Materials & Methods: In this study pharmaceutical dosage form of OT with different brands at a
concentration of 5 and 10 IU/ml was prepared from a local pharmacy. A previously published method
was optimized for the conditions in our laboratory. High Performance Liquid Chromatography
(HPLC) was used as the preferred analytical tool. The method used a C18 column. The mobile phase
consist of acetonitrile/ phosphate buffer with (pH= 5, 0.08 M) (20:80) and UV detection at 220 nm.
Results: The results of these experiments showed a linear standard curve for OT over the range of 0.5-
12 IU/ml. The corresponding regression equation was A=133.1C-2.193 with an r2 value of 0.99. The
Inter-day coefficient of variation for the method ranged between 1.97 IU/ml and 9.93 IU/ml% and the
Intra-day value ranged between 1.10 IU/ml and 1.76 IU/ml. The accuracy of method range was
between 96.40% and 107.5% for Inter-day analysis and 93% and 99.6 % for Intra-days analysis. The
lower limit of quantification was 0.25 IU/ml. The percentage content, taking one of the bulk samples
as 100% references, was 107-120% and 114.2-216.6% recovery of the label claim for OT of 10IU/ml
and OT of 5 IU/ml, respectively.
Conclusion: These findings confirm that the amount of oxytocin in some of dosage forms is higher
than the declared amounts. This study emphasizes on the necessity of quality and accurate controls
over the industrial pharmaceutical.