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Richard B. Horenstein, MD, JD

Academic Title:

Associate Professor

Primary Appointment:



HH 494

Phone (Primary):

(410) 706-0154


(410) 706-1622

Education and Training

  • Yale College, BA, 1986
  • Yale Law School, JD, 1990
  • Jefferson Medical College, MD, 1997
  • Residency, Internal Medicine, University of Michigan Health System, 2000
  • Fellowship, Endocrinology, University of Maryland Medical Center, 2003


Dr. Horenstein has extensive experience in clinical research and has implemented several large translational gene x environment and pharmacogenetics studies at the University of Maryland. He has received an NIH Bench to Bedside award, the focus of which was to translate basic genetic findings into the clinical arena. Dr. Horenstein has substantial expertise in cardiovascular pharmacogenomics where he has led or participated in several investigations including the first NHLBI sponsored prospective pharmacogenetics trial (the COAG Study) where he was the University of Maryland site PI and served both on the study’s Steering Committee and as Chair of the Measurement and Quality Assurance Subcommittee. In his role at the University of Maryland Amish Research Clinic, he has performed detailed phenotyping of carriers of rare gene variants, including studies that use high fat feedings, plant sterol supplements, and IVGTTs to assess the effect of these variants on fasting and post prandial lipid, glucose, and inflammatory marker measures.  He is active in recent efforts to translate pharmacogenetics findings into the clinics and serves as a member of the Pharmacogenetics Service.

Highlighted Publications

Pollin T, Damcott C, Shen H, Ott S, Shelton J, Horenstein R, Post W, McLenithan J, Bielak L, Peyser P, Mitchell B, Miller M, O’Connell J, Shuldiner A.  A Null Mutation in Human APOC3 Confers a Favorable Plasma Lipid Profile and Apparent Cardioprotection. Science 2008;322:1702-1705.

Shuldiner A, O’Connell J, Bliden K, Gandhi A, Ryan K, Horenstein R, Damcott C, Pakyz R, Gibson Q, Pollin T, Post W, Parsa A, Mitchell B, Faraday N, Herzog W, Gurbel P.  Cytochrome p450 2C19 Genotype is a Major Determinant of the Anti-Platelet Effect and Clinical Efficacy of Clopidogrel Therapy. JAMA 2009;302:849-857.

Horenstein R, Madabushi R, Zineh I, Yerges-Armstrong, LM, Peer CJ, Schuck RN, Figg WD, Shuldiner, AR, Pacanowski MA, Effectiveness of clopidogrel dose escalation to normalize active metabolite exposure and antiplatelet effects in CYP2C19 poor metabolizers. Clin Pharmacol. 2014 Aug;54(8):865-73.

Albert J, Yerges-Armstrong L, Horenstein R, Pollin T, Sreenivasan U, Chai S, Blaner W, Snitker S, O'Connell J, Gong D, Breyer R, Ryan A, McLenithan J, Shuldiner A, Sztalryd C, Dancott C. Null mutation in hormone-sensitive lipase gene and risk of type 2 diabetes. New Engl J Med 2014;370:2307-15.

Additional Publication Citations

My complete bibliography is accessible online at:

Research Interests

Pharmacogenetics, CYP2C19, gene variants which effect metabolism

Clinical Specialty Details

Type 2 Diabetes; Thyroid Cancer; Lipid Disorders