Background Complex medication regimens may cause non-adherence. It is not known to which extent regimens can be simplified by using combination and sustained release drugs and whether such simplifications ‘survive’ in the outpatient setting.

Purpose To investigate the development of medication complexity at the border between ambulatory and hospital care and the benefit of a pharmacist's intervention to minimise complexity.

Materials and methods In a prospective study complexity of medications of 240 hospital patients was analysed at times of admission, discharge and six weeks postdischarge using the Medication Regimen Complexity Index (MRCI-D). General practitioners (GPs) were questioned about the discharge medication and reasons to (dis-)continue it. In the intervention group, a pharmacist recommended simplifications for each individual regimen.

Results In the control group (n=109) complexity of the therapy regimens was comparable before, during and after hospital stay (MRCI-D= 13.27, 13.72, 13.73, respectively). In the intervention group (n=131) complexity of the discharge medication was reduced by the intervention to 85.2%, but increased again after discharge to 94.7% of the original value. For 48.6% of the patients medications were modified in hospital. The modifications were judged to improve therapy by 24.3% of the GPs and to impair it by 18.9%. Although around 80% of the GPs indicated willingness to accept drug-related recommendations from hospital and recognised the correlation between complexity and non-adherence, only 50% would accept a higher burden on their budgets for a more effective, but more expensive therapy.

Conclusions Medication regimens can be simplified by maximising the use of combination and sustained release drugs as recommended by a hospital pharmacist. However, this effect is partly reversed when patients return to the outpatient setting. One reason may be the higher costs of these drug formulations that GPs are not always willing to accept.