To model the cost effectiveness of paliperidone palmitate (paliperidone long-acting injectable; PLAI), a new once-monthly long-acting antipsychotic therapy, compared with risperidone long-acting injectable (RLAI) and olanzapine pamoate (OLAI), in multi-episode patients (two or more relapses) with schizophrenia in Sweden.
A Markov decision analytic model was developed to simulate the history of a cohort of multi-episode patients transitioning through different health states on a monthly basis over a 5-year time horizon from the perspective of the Swedish healthcare system. Therapeutic strategies consisted of starting treatment with RLAI (mean dose 37.5 mg every 2 weeks), PLAI (mean dose 75 mg equivalent (eq.) every month) or OLAI (150 mg every 2 weeks or 300 mg every 4 weeks). Probability of relapse, level of adherence, side-effects (extrapyramidal symptoms, tardive dyskinesia, weight gain and diabetes) and treatment discontinuation (switch) were derived from long-term observational data when feasible. Incremental cost-effectiveness outcomes, discounted at 3% annually, included cost per quality-adjusted life-year (QALY) and cost per relapse avoided (expressed in 2009 Swedish Krona SEK).
Relative to RLAI and OLAI, PLAI is economically dominant: more effective (additional QALYs, less relapses) and less costly treatment option over a 5-year time horizon. The results were robust when tested in sensitivity analysis.
The impact of once-monthly treatment on adherence levels is not yet known, and not all variables that could impact on real-world outcomes and costs were included in this model.
PLAI was cost saving from a Swedish payer perspective compared with RLAI and OLAI in the long-term treatment of multi-episode (two or more relapses) schizophrenia patients.