Discussion
As compared with placebo, augmentation with
risperidone in patients who had a limited response
to clozapine alone offered no benefit during
the eight-week, double-blind portion of this
study. Our confidence intervals suggest that we
can exclude a beneficial effect of risperidone augmentation
that would be associated with a moderate-
to-large effect size. In other words, if there
is a beneficial effect of risperidone augmentation,
the magnitude is likely to be smaller than
the benefit associated with changing a group of
treatment-resistant patients from typical antipsychotic
drugs to clozapine.31 We may have failed
to detect a smaller benefit or a benefit that might
have emerged after a longer course of treatment.
The present results are most consistent with those
of a smaller study that reported an advantage of
placebo over risperidone for augmentation of clozapine
treatment.6 Both studies used a method of
data analysis that included all time points sampled.
Another study reported an advantage of risperidone
augmentation7; this study analyzed only