Final answer:
Fasting dogs and cats for 12 hours before a biochemical assay is recommended to avoid lipemia, which can interfere with blood test results, particularly affecting the bioanalysis of pharmacokinetic studies.
Step-by-step explanation:
Ideally, before performing a biochemical assay, dogs and cats should be fasted for 12 hours to avoid lipemia. This fast helps to reduce the risk of high levels of fats in the blood, which can interfere with the results of blood tests, including measurements of various metabolites in plasma. Fasting also decreases variations in glucose levels that could lead to hyperglycemic values. It is not specifically aimed at preventing hepatocellular damage or vomiting from anesthesia; however, fasting could theoretically help with the latter if the animal is undergoing a procedure requiring anesthesia. Fasting is defined as a post-absorptive state, typically commencing 12-14 hours after the last meal, causing a switch to bodily energy sources like fat stores, leading to changes in liver glycogen, blood glucose, and increases in ketone bodies. These changes can affect the bioanalysis and pharmacokinetics of test compounds, as metabolic function is altered, possibly affecting drug binding to plasma proteins and the clearance of metabolites.