Prescription Drug Coverage; Requires individual & group health insurers & HMOs to provide notice of prescription drug formulary changes; specifies requirements for notice of medical necessity submitted by treating physicians; specifies coverage requirement & restrictions on coverage modification by insurers & HMOs receiving such notice; requires insurers & HMOs to maintain record of formulary changes; requires small employer carriers to comply with requirements for prescription drug formulary changes; requires insurers & HMOs to apply reductions in out-of-pocket expenses for prescription drugs toward cost-sharing obligations.