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Lubiprostone is a generic drug. What agents check before quoting it: how many 2026 Part D plans cover it, on which tier, with what restrictions and copays, by plan type, carrier and state.
In 2026, 5,426 of 5,496 Medicare Part D and Medicare Advantage drug plans (98.7%) list Lubiprostone on their formulary, across 324 of 328 formularies. The most common placement is tier 3 (3,841 plans, 70.8% of those covering it). 0 of the covering plans require prior authorization (0%), 0 step therapy and 5,111 a quantity limit.
1,772 covering plans charge a flat copay for a 30-day supply at a preferred retail pharmacy after the deductible — median $47, 304 of them $0; 3,654 charge coinsurance instead — median 25% of the drug's cost. Once a member's out-of-pocket drug spending reaches $2,100 in 2026, covered drugs cost $0 for the rest of the year.
2025: 4,413 of 5,631 plans covered it (78.4%); 2026: 5,426 of 5,496 (98.7%).
Of 4,368 plans offered in both years, 909 added it to the formulary and 0 dropped it.
Among plans covering it both years, 148 moved it to a higher tier and 202 to a lower one; 0 added prior authorization and 0 removed it.
Medicare Part D paid for 632,730 30-day fills of Lubiprostone in 2024 for about 120,987 enrollees, at an average total cost of $88.79 per 30-day fill (CMS Part D Prescribers by Geography and Drug, national).
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Free tools for licensed insurance agents. Data from CMS public files; verify with plan documents before advising a client.
Counts are over every Medicare Advantage drug plan and stand-alone Part D plan in the CMS monthly formulary files, excluding employer plans. A plan counts as covering a drug when any strength or form of it is on the plan’s formulary; the tier, prior authorization, step therapy and quantity limit shown are the most favorable version on that formulary. Copays are for a 30-day supply at a preferred retail pharmacy after the deductible. This is a reference for licensed agents, not a plan recommendation; verify with the plan’s formulary before advising a client. Source: CMS Part D formulary files (release 09/16/2026). CMS formulary data.