The IRS has stated that Medicare premiums withheld from SS can be treated as self-employed health insurance for the purpose of obtaining an above the line (100%) deduction in some cases. This is more advantageous than deducting the premiums as a part of itemized deductions since A) you have to be able to benefit from itemizing and B) only medical expenses in excess of 7.5% of AGI (10% for years 2013 and beyond if not 65+ years old) may be deducted.
The taxpayer must get reimbursed by the business for premiums paid personally/directly. In the case of S-corp owners, the premiums must be included as wages for federal and state tax purposes in accordance with standard procedures for deducting owner health insurance premiums above the line. Constructive ownership rules apply. (Spouse and some other relations' premiums treated as your own.)