Alcohol in the body

Editor—Paton implies that elimination of alcohol from blood is always linear with time—that is, zero order kinetics apply.¹ He also says that the process is mediated by enzymatic conversion. Enzyme activity, for most cases, can be assumed to follow first order reaction rates except when the rate limiting reaction is “saturated.”

This point of saturation occurs for ethanol catabolism, in most non-Asian people, at somewhere between 55 mmol and 65 mmol of ethanol per litre of blood. Below these concentrations, alcohol elimination will proceed under conditions of first order kinetics. The characteristics for the individual at a given time may be determined by serial estimation of alcohol and subsequent calculation.

As said in the article, these characteristics may fluctuate between and within individuals depending on conditions at the time. The suggestion that alcohol is always eliminated by zero order kinetics is wholly misleading and can be dangerous if calculation of elimination of alcohol—for example, before administration of dimercaprol—is required.