Most of the orally administered isoniazid is meta bolically converted to derivatives
that posses virtually no antimicrobia activity. The most abundant of these metabolites is
the acetyl derivatives; smaller but significant amounts of other conjugate, and clevage
products are also found in the blood and urine of patients given isoniazid. Individual
patients vary widely in the degree to which they metabolically alter isoniazid ; some
persons may excrete only 1 per cent of a given dose in the free form, whereas others
may excrete 35percent or more of the dose as unmetabolized drug. Despite this wide
variation amount different persons, an individual demonstrates the same genera1 type of
metabolic pattern on repealed testing. Moreover, persons who excrete only small
amounts of drug in the free from usually have low concentration of biologically active
drug in the serum ,whereas those who excrete large amounts of unconjugated drug in
the urine in general have correspondingly higher concentration of biological1y active
drug in the serum. These observations have led to the concept of "rapid inactivators"
and "slow inactivarots" with a group of "intermediate inactivators" between these two
extremes. The criteria for dividing patients into these groups on serum concentration sof
biologically active drug six hours after the oral administration of a single dose, 4㎎/㎏.
of isoniazid. Persons whose strum isoniazid concentrations are 0.2mcg./㎖ or less
regarded as rapid inactivativators; those with a serum concentration of 0.8mcg./㎖. or
more are regarded as slow inactivators; intermediate inactivators are those in whom the
test dose of drug produces serum concentrations midway between these two extremes,
i.e.,0.4mcg./㎖. Some reports have suggested that components of diet, the time
relationship between meal and isoniazid administration, and genetic factor etc., play a
certain role on isoniazid metabolism. The purpose of this study is to determine the
pattern of INH metabolisms in Koreans.
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