The authors' findings permit a conclusion that the risk of ethmozine overdosage leading to undesirable side effects (dryness in the mouth, noise in the ears, a 'net' in eyes; giddiness, nausea, vomiting) is very high when routine ethmozine doses are administered to patients with grave (Stages II-III) impairments of liver function; this is explained by (1) reduced rate of ethmozine biotransformation, this resulting in a heightened concentration of the drug in the blood, and (2) by an increase of the drug free fraction concentration due to its reduced ability to bind with the blood plasma proteins. This necessitates a pharmacokinetic monitoring of such patients prescribed ethmozine and a correction of the drug dose, if necessary.