The long-term treatment with tamoxifen can alter the lipid profile of patients with breast cancer. Only a few studies associated the plasma concentrations of tamoxifen, endoxifen, and 4-hydroxytamoxifen with blood lipids, which is relevant as the distribution of these compounds for the tissues can be changed, negatively affecting the treatment. The variations in lipids also can account for the high interindividual variation in plasma concentrations of these compounds. The aim of this preliminary study was to associate the plasma levels of tamoxifen and the active metabolites with the lipid levels. An observational study of cases was conducted in patients with breast cancer using tamoxifen in a daily dose of 20 mg. The lipids were measured by spectrophotometric methods and the plasma concentrations of tamoxifen, endoxifen, and 4-hydroxytamoxifen by high-performance liquid chromatography. A total of 20 patients were included in the study. The median plasma concentrations of tamoxifen, 4- hydroxytamoxifen and endoxifen were 62 ng/mL, 1.04 ng/mL and 8.79 ng/mL. Triglycerides levels ranged from 59 to 352 mg/dL, total cholesterol from 157 to 321 mg/dL, LDL-c from 72 mg/dL to 176 mg/dL and HDL-C from 25.1 mg/dL to 62.8 mg/dL. There were no significant associations between the plasma concentrations of tamoxifen, 4-hydroxytamoxifen, and endoxifen with the levels of triglycerides and total cholesterol. The multivariate analysis revealed a weak association between plasma concentrations of tamoxifen and the active metabolites with HDL-c, LDL-c and VLDL-c. This finding provides preliminary evidence of the low impact of lipoproteins levels in the exposure to tamoxifen, 4-hydroxytamoxifen and endoxifen.

Pharmaceutical-Biochemistry graduated from the Center for Higher Education of Pará (1995), Master in Biological Sciences-Neurosciences from the Federal University of Pará (2001) and Ph.D. candidate at the Postgraduate Program in Neuroscience and Cell Biology at the Federal University of Pará (2021) with a concentration area in Cell Biology. She is trained in Endocrine Physiology and has worked with research involving Atrial Natriuretic Peptide and basal secretion in an isolated atrium model. She develops studies with breast cancer patients in anticancer therapies, evaluating metabolic markers, visual and drug metabolism, focused on the quality of life and survival of patients. She currently holds the position of Adjunct Professor at the Faculty of Pharmaceutical Sciences of the Health Sciences Institute of the Federal University of Pará and has professional technical experience in Pharmaceutical Assistance in the Hospital and Clinical Pharmacy, Community Pharmacy and Clinical Analysis segments.