Diffusion of a new drug: a comparative analysis of adoption, treatment complexity, and persistence of risperidone long-acting injectable therapy in the Netherlands.

OBJECTIVE

The study's objective was to analyze the adoption and persistence of risperidone long-acting injectable (RLAI) therapy after its introduction in the Netherlands in 2003 compared with the adoption and persistence of existing first-generation antipsychotic (FGA) depot drugs as an example of the diffusion of a new drug in the Netherlands.

METHODS

Data on antipsychotic use were obtained from the InterAction DataBase (IADB.nl), a database containing pharmacy dispensing records of patients in the northern Netherlands, from May 20, 2003, to December 31, 2006. Treatment complexity for patients prescribed RLAI was analyzed on the basis of psychotropic comedication at baseline and during treatment, as well as on the number of previous antipsychotic therapies. Differences in treatment complexity between patients using RLAI and those using FGA depot drugs were estimated using parametric regressions. To evaluate persistence, survival analysis techniques were applied to estimate the probability of patients continuing the use of RLAI or FGA depot drugs over time.

RESULTS

Data on 435 patients who were treated with depot antipsychotics were extracted from the IADB.nl. Patients had a mean (SD) age of 40.7 (13.8) years, and 65% of them were male. The results of this analysis indicated that persistence for patients prescribed RLAI was significantly lower compared with other depot antipsychotics (RLAI vs zuclopenthixol, P = 0.002; RLAI vs all other depot antipsychotics, P = 0.009). At the initiation of treatment, patients prescribed RLAI had more previous psychotropic comedication and had, on average, approximately 5 and approximately 1.5 times more prior depot drug therapies compared with zuclopenthixol and any other FGA depot drug, respectively.

CONCLUSIONS

The findings of this study suggest that RLAI has been prescribed more often for difficult-totreat patients than have other available depot antipsychotics. This may explain the low adoption and poor persistence observed in the first few years after the introduction of RLAI. Further research with more extensive data should be pursued to obtain better understanding of the current diffusion of RLAI in daily clinical practice.