Customers of Minnetonka-based UnitedHealth Group Inc. (UNH) who use certain asthma drugs and antidepressants will soon get a price break.

The health-insurance giant will soon offer $20 discounts off monthly co-pays for members who refill certain prescriptions within about 30 days after the last prescription runs out -- essentially rewarding patients for adhering to treatment plans, Tim Heady, head of UnitedHealth's pharmaceutical solutions unit, said this week.

The eligible asthma drugs include GlaxoSmithKline PLC's Advair and AstraZeneca PLC's Symbicort. The antidepressants include Eli Lilly & Co.'s Cymbalta, and Wyeth's Effexor XR and Pristiq. These drugs carry $50 co-pays on some UnitedHealth preferred-drug lists, so the discounts would reduce members' out-of-pocket costs to about $30.

The so-called "adherence incentive" discounts will begin Oct. 1 for most of UnitedHealth's 8 million fully insured members, and on Jan. 1 for a small percentage of them. The program is "cost-neutral" to UnitedHealth's employer customers because the discounts are at least partially factored into UnitedHealth's rebate contracts with drug manufacturers.

For drugmakers, the discounts may help maintain market share for brand-name drugs at a time when the weak economy has caused consumers to put off filling prescriptions or switch to cheaper generics.

Non-adherence to prescriptions for chronic conditions can lead to costly complications over time. Some pharmacy-benefit management companies make reminder phone calls to members if they're late making a refill. Last year, in a similar move, UnitedHealth introduced a health plan for self-insured employers where preventive diabetes care is fully covered.