The study was conducted to compare the bioavailability of two formulations of Risedronate Sodium 35 mg tablet (risedronate sodium of Aché S/A test formulation and Actonel® from Sanofi-Aventis Pharmaceuticals Inc. reference formulation, Brazil) in 80 volunteers both sexes. This was an open, randomized, two-sequence, two-period, crossover single dose two treatments, in which a group of volunteers received the test formulation and the other reference formulation. Blood samples were obtained throughout a 96 hours interval. The risedronate sodium concentrations were determined by mass spectrometry (UPLC-MS-MS) using risedronic acid-D4 (deuterated risedronate) as internal standard. From the data obtained, calculate the following pharmacokinetic parameters: AUC 0-t, AUC 0-∞ and Cmax. The geometric mean of risedronate sodium /Actonel ® 35 mg were 101.90% for AUCO-t, 97.95% for AUC 0-∞ and 100.70% for Cmax. The 90% confidence intervals were 86.43%-120.14%, 83.04%-115.54% and 85.50%-118.61%, respectively. Since the confidence intervals 90% for Cmax and AUC0-t was within the range 80%-125% proposed by the FDA and ANVISA (National Agency of Sanitary Surveillance in Brazil), it is concluded that the tablet of sodium risedronate 35 mg was bioequivalent to Actonel ® tablet of 35 mg and thus the test product may be considered interchangeable in medical practice. © Copyright Moreira Jr. Editora. Todos os direitos reservados.698-9225229Souza, P.M., Diagnóstico e tratamento da osteoporose (2010) Rev Bras Ortop, 45, pp. 220-229Chesnut, C.H., Treatment of postmenopausal osteoporosis (1984) Compr Ther, 10, pp. 14-17Marshall, D., Johnell, O., Wedel, H., Meta-analysis of how well measures of bone mineral density predict occurrence of osteoporotic fractures (1996) British Medical Journal, 312 (7041), pp. 1254-1259Szejnfeld, V.L., Osteoporosis (2004) Revista Brasileira de Medicina, 61 (7), pp. 417-428Nordin, B.C., Chatterton, B.E., Need, A., Horowitz, M., The definition, diagnosis and classification of osteoporosis (1997) Phys Med Rehabil Clin North Am, 6, pp. 395-414Whedon, G.D., Osteoporosis (1987) N Engl J Med, 6, pp. 397-398Brewer, V., Meyer, B.M., Keele, M.S., Role of exercise in prevention of involutional bone loss (1983) Medicine and Science in Sports and Exercise, 15 (6), pp. 445-449Cimaz, R., Biphosphonates in pediatric rheumatic diseases (2003) Pediatric Rheumatology on Line Journal, 1, pp. 134-139Licata, A.A., Bisphosphonate therapy (1997) American Journal of the Medical Sciences, 313 (1), pp. 17-22. , DOI 10.1097/00000441-199701000-00004Fleisch, H.A., Bisphosphonates: Preclinical aspects and use in osteoporosis (1997) Annals of Medicine, 29 (1), pp. 55-62Weinstein, R.S., Roberson, P.K., Manolagas, S.C., Giant osteoclast formation and long-term oral bisphosphonate therapy (2009) N Engl J Med, 360, pp. 53-62Brookler, K., Medical treatment of otosclerosis: Rationale for use of bisphosphonates (2008) Int Tinnitus J, 14, pp. 92-96Heikkinen, J.E., Selander, K.S., Laitinen, K., Arnala, I., Vaananen, H.K., Short-term intravenous bisphosphonates in prevention of postmenopausal bone loss (1997) Journal of Bone and Mineral Research, 12 (1), pp. 103-110. , DOI 10.1359/jbmr.1997.12.1.103Warner, C., (2011) Risedronato de Sódio Comprimidos: Informações de Prescrição, , Rockaway, NJMcClung, M.R., Geusens, P., Miller, P.D., Zippel, H., Bensen, W.G., Roux, C., Adami, S., Chestnut III, C.H., Effect of risedronate on the risk of hip fracture in elderly women (2001) New England Journal of Medicine, 344 (5), pp. 333-340. , DOI 10.1056/NEJM200102013440503Russell, R.G.G., Rogers, M.J., Bisphosphonates: From the laboratory to the clinic and back again (1999) Bone, 25 (1), pp. 97-106. , DOI 10.1016/S8756-3282(99)00116-7, PII S8756328299001167