Complex sentence: For the drugs which rapidly undergo metabolism clearance is dependent on the hepatic blood flow, whereas for drugs which slowly undergo metabolism changes in the unbound fraction of the drug directly changes the clearance of the drug.
Split into simpler sentences: For the drugs which rapidly undergo metabolism, clearance is dependent on the hepatic blood flow. In contrast, for drugs which slowly undergo metabolism, changes in the unbound fraction of the drug directly changes the clearance of the drug.