Our Leadership
Meet Our Leadership Team

The MedMark Services leadership team consists of industry pioneers and experienced clinicians in the fields of primary care and addiction services. With a combined 115 years of experience, our team is committed to providing the highest quality care in an environment of dignity and respect.
David K. White, Ph.D.
President and CEO
With more than two decades of health care administration experience in psychiatric care and substance abuse, physical rehabilitation, long term care and acute hospital services, Dr. David White joined MedMark as President and CEO in January of 2008. Prior to joining the company, he served as President, Contract Management Services for Nashville-based Psychiatric Solutions, Inc. Previously, he was President and Chief Operating Officer of Horizon Health Corporation, where he oversaw expansion and acquisition strategies, resulting in impressive growth. He also served in a number of senior management roles during his twelve year tenure at Horizon. Prior to Horizon, Dr. White was the CEO of Charles River Health Management, a psychiatric contract management company in Boston and Charles River Hospital, a specialty psychiatric and substance abuse hospital also in Massachusetts. He received a bachelor’s degree in science from Tufts University in Medford, Mass., and obtained master’s and doctoral degrees in clinical psychology from Vanderbilt University in Nashville. 
Ronald Rubin
Chief Financial Officer
Ronald Rubin joined MedMark Services, Inc. as Chief Financial Officer in December 2008. He has over 30 years of experience in the field of Finance, and over 15 years as CFO of companies in a variety of industries. Ron had been CFO in private-equity backed companies since 1997, with some significant successes in value creation. In his first encounter, at Galaxy Aerospace Company, he joined the company as CFO at inception. Four years later, this firm had increased revenues tenfold, and was sold to a competitor resulting a very significant gain by the investors. Prior to joining MedMark, Ron was CFO and Controller of Bell/Agusta in a joint venture between Bell Helicopter and an Italian company. Ron holds a Bachelor of Engineering degree from The Cooper Union, and a Master of Science from Carnegie-Mellon University. He earned a Master of Business Administration with a concentration in Finance from the University of Tulsa. He has also taught Finance courses in the MBA program at Fairleigh Dickenson University.
Frank Baumann
Vice President of Development
Frank Baumann joined MedMark Services as Vice President of Development in April of 2009. Frank is a very experienced senior executive with over 16 years of psychiatric and substance abuse experience with a vast array of management expertise including national multi-site operations, strategic planning, business development and finance. Frank comes to MedMark from Horizon Health Corporation where he spent over a decade and held key leadership roles including President of Hospital Services, President of Contract Management Services and Senior Vice President of Operations. Prior to his term with Horizon Health, Frank spent several years with Mountain Crest Behavioral Healthcare System in Fort Collins, Colorado as CEO as well as Controller. Frank earned a Bachelor of Science Degree in Business Administration - Accounting from Colorado State University and a MBA from the University of Denver. 
Sheldon Glass
National Medical Director. Addiction Treatment Services

Sheldon D. Glass, M.Ed., M.D., was appointed National Medical Director for MedMark Services on December 1, 2011. Dr. Glass developed the Glass Health Programs in Maryland which currently serves approximately 3,000 people each day. Dr. Glass has been board certified in Psychiatry, Addiction Medicine, Adolescent Psychiatry and Pediatrics. He has been on the staff of the Johns Hopkins School of Medicine since 1964, and currently is the Chair of their Advisory Council for Counseling and Behavioral Services in the Department of Education. He is on the Board of Directors of Friends Research Institute and sits on the governing council for the American Society of Adolescent Psychiatry. He will oversee the medical quality of MedMark’s opioid treatment programs and other addiction treatment services.
Jeffrey A. Lempert, M.D.
National Medical Director, Veteran's Affairs
An experienced practitioner in the fields of internal medicine and primary health services, Dr. Jeffrey Lempert serves as National Medical Director for MedMark Services and has been with MedMark since 2003. For more than thirty years, Dr. Lempert has contributed to the expansion and success of multi-specialty medical groups as well as primary care practices nationwide. He offers the unique combination of clinical knowledge and technological expertise. Prior to joining MedMark, Dr. Lempert worked for more than 25 years as a member of the Mount Kisko Medical Group in Mount Kisko, New York, and was on the medical staff of the Northern Westchester Center in Westchester, New York. Dr. Lempert plays a critical role in MedMark's partnership with the U.S. Department of Veterans Affairs in leading the company's national community-based outpatient clinics. A graduate of Boston University School of Medicine, Dr. Lempert is board certified in internal medicine and completed post-graduate training at Boston University Medical Center. He has been recognized by the National Institutes of Health and holds medical licensure in New York, Florida, California, Indiana, Georgia, New Hampshire and Massachusetts. 
Joanne Prada
Vice President, OTP Operations
Joanne Prada joined MedMark Services, Inc. in August 2010 as Regional Director, Operations. She has over 25 years of senior healthcare management experience. Prior to joining MedMark, she had been self employed as a healthcare management consultant. Prior to this, she worked for DaVita, Inc, a national leader in dialysis services, for 14 years where she ultimately served as Division Vice President overseeing 54 locations in California, Washington, Oregon and Nevada. Prior to that she served as Director of Operations for HemaCare Corporation and as Facility Director for NephroCare. She also worked for National Medical Care, Inc. as an administrator overseeing three outpatient dialysis centers. Joanne received her B.S. in Business Management from the University of Phoenix. 
Robin A. Johnson
Vice President, Sales and Marketing
Robin Johnson joined MedMark Services, Inc. as Vice President, Sales and Marketing in July 2009. Robin provides marketing, referral development consultation and support to all MedMark locations as well as new acquisitions. Robin is an experienced marketing professional with over 20 years of experience focused on marketing behavioral health and substance abuse services. Prior to joining MedMark Services, she worked with the Devereux Foundation as National Director of Business Development and Horizon Health as Vice President, Business Development and Marketing. Ms. Johnson received her Bachelor of Science degree in Business with a concentration in Marketing from Rivier College, New Hampshire. 
Sharon Dembinski
Director of Quality and Clinical Services
Sharon Dembinski joined MedMark Services, Inc. in January, 2009 as Director of Quality and Clinical Services. She spent the last 20 years as a provider of both hospital-based care and substance abuse treatment. Prior to joining the company, she worked as a Nurse Practitioner for substance abuse treatment provider Discovery House / Smart Management of Providence, Rhode Island. There she worked with the Corporate Medical Team developing policy and risk management tools. Sharon's areas of expertise are opioid dependence, medication assisted addiction treatment, methadone treatment during pregnancy, and patient advocacy. Sharon has lectured extensively on methadone, pregnancy and the newborn and also volunteers for Methadone Support Organization as an administrator and counselor for expectant and postpartum women. She is the former New England Regional Director for the National Alliance of Methadone Advocates (NAMA), the recipient of the 2006 NAMA Advocate of the Year Award, and was named RICARES Substance Abuse Treatment Provider of the Year Award in 2008. Sharon earned both her bachelor’s degree and master’s degree in nursing at Simmons College in Boston.
Tracy S. Sims, M.A.
Director of Veteran’s Affairs Operations
Mrs. Sims brings more than 17 years of clinical experience to her position as Director of Veteran’s Affairs Operations with MedMark Services. An experienced professional, she previously served as a National Clinic Specialist for Sterling Medical Corporation where she oversaw the operations of their community-based outpatient clinics dedicated exclusively to serving our nation’s veterans. Tracy is a certified medical assistant and a graduate of Webster College. She is active in numerous civic and charitable organizations, having served the Girl Scouts of America and various veterans’ organizations for more than 20 years. 

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