Final answer:
Blocking of enterohepatic circulation can lead to increased serum concentrations of drugs, as their metabolism and elimination are disrupted. This can pose a risk of toxicity, especially if pre-existing liver conditions such as cirrhosis or portal hypertension are present. Dosage adjustments may be required to prevent adverse effects.
Step-by-step explanation:
If enterohepatic circulation is blocked, it results in a significant impact on the serum level of a circulating drug. Enzymes involved in the metabolism and recycling of drugs can no longer function appropriately, causing a disruption in the drug's elimination process. Normally, drugs are secreted into bile, which then enters the intestines and can be reabsorbed into the bloodstream. Without this recirculation, more of the drug remains in the systemic circulation for a longer period. This can lead to an increase in the serum concentration of the drug, potentially leading to toxicity.
Moreover, if conditions like liver disease or portal hypertension are present, the liver's functionality is severely impacted. The filtration and detoxification processes are compromised, so even blood that traverses the liver may not be properly detoxified. In terms of pharmacokinetics, the obstruction reduces drug clearance and could consequently result in an unintended prolongation of the drug's effect, necessitating adjustments in dosing regimens to avoid possible adverse effects or toxicity.