Here is the design of a clinical trial:

Official Title: Evaluation of the Impact of Tacrolimus-based Immunosuppression on Heidelberg Liver Transplant Cohort (HDTACRO): Study Protocol for an Investigator Initiated, Non-interventional Prospective Study

Included conditions:
- Liver Transplantation

Study Armgroups:
- {'label': 'Tacrolimus-based immunosuppression', 'description': 'Similar to the clinical routine, as soon as a patient is able to swallow and has a sufficient gastrointestinal activity, Tacrolimus-based immunosuppression using Prograf®, Advagraf® or Envarsus® will be started.', 'interventionNames': ['Drug: Tacrolimus']}

Interventions:
- {'type': 'DRUG', 'name': 'Tacrolimus', 'description': "Similar to the clinical routine, as soon as a patient is able to swallow and has a sufficient gastrointestinal activity, Tacrolimus-based immunosuppression using Prograf®, Advagraf® or Envarsus® will be started. Furthermore, calcineurin inhibitors-based immunosuppression will be used (initial dose based on the patients' body weight) with the goal of tough levels of 3-7 ng/mL in the first seven days after liver transplantion, depending on immune status and indication for transplantation. Further tough levels will be determined based on factors such as patients' history and indication for liver transplant.", 'armGroupLabels': ['Tacrolimus-based immunosuppression']}

Primary Outcomes:
- {'measure': 'The number of required dose adjustments of Tacrolimus formulations used in clinical routine for achieving the target tough level', 'timeFrame': 'Six months'}

Please estimate the sample size based on the assumption: 
No formal sample size estimation was carried out. The study is not confirmatory, and no specific assumptions on significance level, power, or missing/dropout rate were mentioned.
2.9.1
          Sample size
          Since no confirmatory approach will be followed in this non-interventional study, no formal sample size estimation was carried out. For practical reasons, the number of included subjects was set to 100, which are deemed to be sufficient to provide stable estimates of the primary variable.