International literature suggests
that co-payment increases are associated with decreased medicine use,
although the effects depend on context. We examined the impact of a
co-payment increase on the consumption of type 2 antidiabetics in
Finland, a country with a comprehensive health and social security
system including ceiling mechanisms aiming to protect patients from high
co-payment expenditures.

We used administrative
register data on all reimbursed purchases of antidiabetics during
2014−2018. An interrupted time series design with segmented regression
was used to examine the mean monthly purchase per person, measured as
Defined Daily Doses (DDDs), before and after the co-payment increase.

At baseline, the mean monthly purchase per person of type 2 antidiabetics was 105 DDDs (95% CI 103.8; 106.0;p<0.001) and there was a decreasing trend of 0.2 DDDs per month (95% CI -0.23;-0.13;p<0.001). A statistically significant decrease of 5.6 DDDs (95% CI -7.3;-3.8;p<0.001)
was detected after the reform; however, no significant change in the
trend was observed. No significant increase was detected in the mean
monthly per person purchase of insulins.

The results
suggest that a co-payment increase decreases consumption of necessary
medicines despite the presence of a medicine co-payment ceiling
mechanism. Whether the decrease was associated with negative health
effects remains to be further investigated.