Prescription Drug and Health Improvement Act of 2007 - Amends title XVIII (Medicare) of the Social Security Act (SSA) with respect to prescription drug plans to repeal the prohibition against interference by the Secretary of Health and Human Services with negotiations between drug manufacturers and pharmacies and prescription drug plan sponsors, and against the Secretary's requiring a particular formulary or instituting a price structure for the reimbursement of covered part D (Voluntary Prescription Drug Benefit Program) drugs. Grants the Secretary authority similar to that of other federal entities that purchase prescription drugs in bulk to negotiate contracts with manufacturers of covered part D drugs.