Assessment of liver function: the current situation.

Hepatologists continue to search for a safe, accurate, and reliable method to quantify hepatic function similar in principle to the creatinine clearance for renal disease or spirometry for pulmonary disease. When evaluating patients with advanced decompensated chronic liver disease, there is little need for such tests and a decision for or against liver transplantation is all that is required. However, in patients with chronic compensated liver disease, an estimate of hepatic function based on objective criteria would be most valuable in establishing a prognosis and in determining a treatment plan. The best methods currently available for this purpose consist of the use of model drugs which are metabolized exclusively by the liver by cytochromes P-450 enzyme systems. The alterations in pharmacokinetic parameters (i.e., clearance rate of the parent compound or formation rate of one of its metabolites, etc.) produced as a result of liver disease can be quantitated. The results obtained can be utilized as a measure of hepatic function. The two drugs most commonly utilized for this purpose are lidocaine and caffeine. The advantages and disadvantages of each of these two drugs as probes of hepatic function are herein reviewed.