Prescription persistence and safety of antipsychotic medication: a national registry-based 3-year follow-up.

PURPOSE: Long-term persistence of use, lack of co-prescribed anticholinergic antiparkinson drugs and low mortality may indicate effectiveness and safety of antipsychotic drugs. We aimed to assess 3-year prescription persistence, concomitant use of anticholinergics and mortality related to the use of all antipsychotic agents available in Norway.
METHODS: Data were drawn from the Norwegian Prescription Database on the sales of antipsychotic and anticholinergic antiparkinson agents in 2004 to a total of 52,427 patients. The primary study group was a subgroup of 34,494 patients who were prescribed only one antipsychotic agent in 2004. The patients were re-investigated in 2007. For each of the 13 antipsychotic agents studied, assumed prescription persistence was assessed in light of use of anticholinergic antiparkinson agents in 2004, and casualty rates were noted.
RESULTS: The highest persistence was demonstrated for zuclopenthixol (69.8%) and clozapine (88.4%). Zuclopenthixol was often co-prescribed with anticholinergics (22.2%), in contrast to clozapine (3.6%). Ziprasidone was associated with a low mortality (OR = 0.08), while chlorprotixene and haloperidol were associated with a high mortality (OR = 1.34 and 3.97, respectively) compared to levomepromazine.
CONCLUSIONS: Clozapine demonstrated a high degree of continuity of prescription and a low level of concomitant use of anticholinergics. Zuclopenthixol also demonstrated a high degree of continuity of prescription, despite a considerable degree of co-prescribed anticholinergics. We did not find that any antipsychotic other than ziprasidone was associated with a low mortality. The use of haloperidol seemed to confer a mortality risk three times that of any of the other antipsychotic agents included.