  Clinical trials in specific indications require the administration of rescue
medication in case a patient does not sufficiently respond to investigational
treatment. The application of additional treatment on an as needed basis causes
problems to the analysis and interpretation of the results of these studies
since the effect of the investigational treatment can be confounded by the
additional medication. Following-up all patients until study end and capturing
all data is not fully addressing the issue. We present an analysis that takes
care of the fact that rescue is a study outcome and not a covariate when rescue
medication is administered according to a deterministic rule. This approach
allows to clearly define a biological effect. For normally distributed
longitudinal data a practically unbiased estimator of the biological effect can
be obtained. The results are compared to an ITT analysis and an analysis on all
patients not receiving rescue.
