S220• OFID 2017:4 (Suppl 1) • Poster Abstracts safety of this practice in the real-world setting. The practice at our institution does not dose-adjust 3TC until CrCl is <30mL/minute; 100-150mg/d is prescribed for hemodialysis and CrCl 5-29mL/minute and 300mg/d for CrCl ≥30mL/minute.Methods. This cross-sectional study included HIV+ men and non-pregnant, non-lactating women aged ≥18 on higher-than-recommended 3TC doses as part of their antiretroviral regimen for ≥ 12 mo. A serum concentration (for Cmin) of 3TC was drawn, then patients were instructed to take their antiretrovirals. A second serum concentration (for Cmax) was drawn 0.5-1.5 h afterwards. An estimated AUC was calculated using physiological-based pharmacokinetic modeling (SimCYP). Lactic acid levels and patient-reported adverse events were obtained to monitor for safety, viral suppression was assessed for efficacy, and concurrent medications were screened.Results. The observed average Cmax values for the various CrCl groups were within therapeutic range. Simulated Cmax values accounted for dose accumulation in renal impairment, thus the calculated AUC values were supratherapeutic. However, all lactic acid levels were within normal limits and no patients reported adverse effects. All patients were virally suppressed. Conclusion. This study is the first to provide evidence on the safety and efficacy of using higher-than-recommended doses of 3TC in a real-world setting. 3TC was very well tolerated at all levels of renal function with normal lactic acid levels and all patients were virally suppressed. These results can guide providers in their selection of higher 3TC dosing in patients with renal impairment to maximize adherence. Background. In some studies, some of the formulated equations of GFR estimation based on serum cystatin C were shown to have no difference in bias and were accurate when compared with equations of GFR estimation based on iothalamate clearance. Dolutegravir (DTG) is an integrase strand transfer inhibitor that is used for the treatment for human immunodeficiency virus (HIV) infection. DTG inhibits organic cation transporter 2 (OCT2) on the basolateral side of proximal tubule cells of the kidney, and leads to increased serum creatinine levels without true renal function deterioration. In HIV patients who receive DTG, an alternative test to serum creatinine measurement is needed to determine the correct renal function.Methods. We retrospectively evaluated 18 HIV-infected men who had received combination anti-retroviral therapy (cART), including DTG, and who had available data on serum creatinine and cystatin C levels. We collected data on serum creatinine and cystatin C levels from two determinations: before, and one month to one year after administration of DTG. We using paired t-test to assess the changes in estimated glomerular filtration rate (eGFR) calculated by serum creatinine or cystatin C level, after the start of cART.Results. In all 18 patients, only 2 cases were naïve, whereas 16 cases switched treatment. For the 16 cases ...