Aims: Darunavir is widely used in HIV/AIDS therapy. It is a HIV protease inhibitor that has excellent efficacyagainstthe virus.The aim of this study is to develop and validate an analytical method fast and free of interferences for determination of darunavir ethanolate as raw material and tablet dosage form. Methodology: As the formulation excipients show high interference in darunavir determination by adirect UV absorption measurement aderivative spectrophotometry was applied. Aselective, easy and fastmethod was achieved employing simple and cheap instrumentation by using first -order derivative spectrophotometry . Results:The first-derivation of spect rum of the drug measured between 200 and 400 nm allowed identification of the analyte and showed absence of placebo interference. The assay was based on the absorbance at 276nm.The linear concentration range was established from 11 to 21 �og/mL. The intra -day and inter-day precision expressed as RSD was 0.06% and 3.75% respectively with mean recovery of 99.84%. Conclusion: The proposed analytical method is able to quantify darunavir as raw material and tablets andcan be used routinely by any laboratory ap plying a spectrophotometer Original ResearchArticle