The purpose of this work was to identify 550 mg sodium naproxen in tablets by infrared spectroscopy, for which the Perkin Elmer-Spectrum TWO infrared spectrometer was used, with Fourier transform and universal refractive accessory, in the range of 450-4000 cm-1. one. As a study material, secondary standard (ES) of naproxen sodium, naproxen tablets 550 mg of an innovative drug (MI) and 13 multi-source drugs (MM) were used. Product specimens of the molecular vibration expressed in wave numbers were obtained, the molecular vibration for OH was a band between 3322 to 3447 cm -1 (ES, MI and MM), for the group C=O it was a signal of 1659-1671 cm-1 (MI and MM M1-M12), the aromatic double bond was 1630-1632 cm-1 (ES, MI and MM M1-M12), for the symmetric COO- 3 different signals 1542-1544 cm-1 were evidenced 1 (MI and MM M2, M3, M7-M12), 1555-1557 cm-1 (MM M4-M6) and 1584 cm-1 (ES and MM M1), thi...