Overall equation for complete oxidation of ingested alcohol (ethanol) to carbon dioxide (CO₂) and water (H₂O)

Ingested alcohol (ethanol) is oxidized in the liver to acetic acid, which is then transferred to other organs where it is completely oxidized to carbon dioxide and water. However, to the best of our knowledge, no overall equation for this process has yet been described in the forensic literature, despite its physiological relevance. Here we present such an overall equation, derived by summing the reactions involved in the complete oxidation of ethanol: oxidation of ethanol to acetic acid by alcohol and aldehyde dehydrogenases, conversion to acetyl-coenzyme A, oxidation via the citric acid cycle, and utilization of the resulting reduced form of nicotinamide adenine dinucleotide and ubiquinol to fully reduce molecular oxygen. The overall equation is expressed as a pair of equations because inorganic phosphate takes two forms, H₂PO₄^- and HPO₄^2-, with a pKa of approximately 6.8. The pair of equations indicates that no H⁺ is generated if inorganic phosphate is present as H₂PO₄^-, whereas one H⁺ is formed if inorganic phosphate is present as HPO₄^2-. The actual ratio of [HPO₄^2-]/[H₂PO₄^-] is approximately 1, 1.6, and 2.5 at pH 6.8, 7.0, and 7.2, respectively, indicating that complete oxidation of one ethanol molecule forms approximately 0.6 (0.5-0.7) H⁺. Evidence of H⁺ formation contradicts the general notion that complete oxidation neither generates nor consumes H⁺. The implications of H⁺ generation merit clarification, particularly given the prevalence of metabolic acidosis in heavy drinkers.