Objective: To evaluate the morphological effects of phenobarbital treatment on new bone formation and on bone marrow biomechanics in Wistar rats. Methods: We used ten rats that were divided into two groups: control (CT) and phenobarbital (FE). The FE group received daily doses of phenobarbital 0.035 ml / kg intramuscularly for 60 days. The CT group received the same dose and route of administration of 0.9% saline solution. After 30 days, we introduced a bone defect in the parietal bone and implanted porous hydroxyapatite (HAP) in cavities in the tibia. After surgery, we continued the protocols until the end of 60 days when the rats were euthanized, and the bones were collected. Results: The volume of bone formed around HAP in parietal defect and biomechanical findings were lower in animals receiving FE compared to CT. Conclusion: Prolonged use of phenobarbital interferes with bone repair after injury, decreasing the osseointegration of HAP implants and making bones less resistant.246794798Pastore, M.E., Ofuchi, A.S., Nishiyama, P., Monitorização terapêutica de fenobarbital (2007) Acta Sci Health Sci., 29 (2), pp. 125-131Silva, H.T., Hartmann, A.A., A relação do uso crônico de fenobarbital com áreas potencialmente pré-neoplásicas em fígado de ratos (2006) Arq Gastroenterol., 43 (2), pp. 121-124Chung, S., Ahn, C., Effects of anti-epileptic drug therapy on bone mineral density in ambulatory epileptic children (1994) Brain and Development, 16 (5), pp. 382-385. , DOI 10.1016/0387-7604(94)90125-2Kruse, K., Bartels, H., Ziegler, R., Parathyroid function and serum calcitonin in children receiving anticonvulsant drugs (1980) European Journal of Pediatrics, 133 (2), pp. 151-156Pack, A.M., Morrell, M.J., Adverse effects of antiepileptic drugs on bone structure: Epidemiology, mechanisms and therapeutic implications (2001) CNS Drugs, 15 (8), pp. 633-642Mascarenhas, N.M., Ideriha, N.M., Orsi, A.M., Alguns eventos morfológicos do processo de reparo de falha óssea diafisária no rádio esquerdo de ratos tratados com fenobarbital (1999) Braz J Vet Res Anim Sci., 36 (4), pp. 188-193Farhat, G., Yamout, B., Mikati, M.A., Demirjian, S., Sawaya, R., El-Hajj Fuleihan, G., Effect of antiepileptic drugs on bone density in ambulatory patients (2002) Neurology, 58 (9), pp. 1348-1353Gascon-Barre, M., Cote, M.G., Influence of phenobarbital and diphenylhydantoin on the healing of rickets in the rat (1978) Calcified Tissue International, 25 (1), pp. 93-97Soares, E.V., Fvaro, W.J., Cagnon, V.H., Bertran, C.A., Camilli, J.A., Effects of alcohol and nicotine on the mechanical resistance of bone and bone neoformation around hydroxyapatite implants (2010) J Bone Miner Metab., 28 (1), pp. 101-107Mandarin-De-Lacerda, C.A., What is the interest of normal and pathological morphological research to be quantitative? The exemple of the stereology (1999) Braz J Morphol Sci., 16 (2), pp. 131-139Weisbroth, S.H., Paganelli, R.G., Salvia, M., Evaluation of a disposable water system during shipment of laboratory rats and mice (1977) Laboratory Animal Science, 27 (2), pp. 186-194Svendsen, P., Hau, J., (1984) Handbook of laboratory animal science, , CRC Press, Boca Raton: CRC PressPalencia, G., Teixeira, F., Ortiz, A., Perez, R., Rios, C., Sotelo, J., Detrimental effects of malnutrition on the damage induced by alcoholism: A study of animal models that simulate chronic alcoholism and malnutrition of large human groups (1994) Journal of Studies on Alcohol, 55 (1), pp. 113-120Verrotti, A., Coppola, G., Parisi, P., Mohn, A., Chiarelli, F., Bone and calcium metabolism and antiepileptic drugs (2010) Clin Neurol Neurosurg., 112 (1), pp. 1-10Parara, E.M., Galanopoulou, P.B., Rallis, G., Vairaktaris, E., Tesseromatis, C.P., Mandibular bone density and calcium content affected by long-term anticonvulsant treatment in rats (2009) J Musculoskelet Neuronal Interact., 9 (1), pp. 32-37Nilsson, O.S., Lindholm, T.S., Elmstedt, E., Fracture incidence and bone disease in epileptics receiving long-term anticonvulsant drug treatment (1986) Archives of Orthopaedic and Traumatic Surgery, 105 (4), pp. 146-149Fraser, W.D., Hyperparathyroidism (2009) Lancet, 374 (9684), pp. 145-158Lee, R.H., Lyles, K.W., Colón-Emeric, C., A review of the effect of anticonvulsant medications on bone mineral density and fracture risk (2010) Am J Geriatr Pharmacother., 8 (1), pp. 34-46Bouillon, R., Okamura, W.H., Norman, A.W., Structurefunction relationships in the vitamin D endocrine system (1995) Endocr Rev., 16 (2), pp. 200-257Broulik, P., Kragstrup, J., Mosekilde, L., Melsen, F., Osteon cross-sectional size in the iliac crest. Variation in normals and patients with osteoporosis, hyperparathyroidism, acromegaly, hypothyroidism and treated epilepsia (1982) Acta Pathologica et Microbiologica Scandinavica - Section A Pathology, 90 (5), pp. 339-344