Patients without diabetes who took metformin along with their second-generation antipsychotic (SGA) to prevent weight gain had better adherence to their antipsychotic than those prescribed SGAs alone, according to a study issued yesterday by Journal of Clinical Psychiatry.
Why It’s Clinically Relevant
“SGA drugs are the cornerstone for the management of severe mental disorders like schizophrenia, bipolar disorder, and major depressive disorder,” wrote Jerusha Daggolu, M.D., at the University of Houston, and colleagues. “Since these conditions often require long-term therapy, it is crucial to maintain consistent medication adherence over time. Weight gain may cause patients on SGAs to discontinue their medications because of concern about their appearance.”
An evidence-based guideline issued earlier this year recommended concurrent prescribing of metformin when initiating or switching SGAs in most cases to mitigate weight gain.
How It Worked
Daggolu and colleagues analyzed claims from the Marketscan commercial insurance database for 575 nondiabetic adults who had 30 days or more of overlapping SGA and metformin prescriptions and 2,300 adults taking SGAs alone. They also assessed claims for 972 Medicaid enrollees taking SGAs plus metformin and 3,888 taking SGAs alone.
By the Numbers
During a 180-day follow-up, concurrent users of an SGA and metformin had a greater proportion of days covered by an antipsychotic prescription (adherence) than those using SGAs alone:
- 81% versus 68% among commercially insured
- 78% versus 68% among Medicaid enrollees
Adults taking concurrent metformin also had greater time to discontinuation (persistence) than those using SGAs alone:
- 139 days versus 106 days among commercially insured
- 149 days versus 115 days among Medicaid enrollees
Both adherence and persistence remained higher in the SGA-plus-metformin group after adjusting for baseline differences between the two groups.
The Other Side
The lack of weight measurements leaves uncertainty about whether the improved adherence was due to reduced weight gain from the metformin, the researchers noted.
What’s Next
“Higher adherence observed in both early and delayed initiators suggests that metformin may be effective in improving SGA adherence when used for either the prevention or treatment of antipsychotic-induced weight gain,” the researchers wrote, adding: “Future study is needed to confirm the causal pathway using linked electronic medical record and claims data.”
(Image: Getty Images/iStock/Shidlovski)
