Accumulation of penicillin in vaginal fluid

The excretion of phenoxymethylpenicillin in vaginal fluid was determined in five women after intake of a single dose of 1 g phenoxymethylpenicillin and in five women on a 10-day medication scheme with 1 g twice daily. After the single dose, there was a steady increase of penicillin in vaginal secretion during the following 3 hours. During the same period, the concentrations in serum and saliva peaked and started to decline. Fifteen hours after intake, vaginal fluid contained more than 1 mg/L, whereas no activity was found in serum or saliva. During the 10-day course of treatment, vaginal concentrations ranged between 2-3 mg/L. The drug was not eliminated from the vagina until the second day after ceasing medication. The accumulation and slow pharmacokinetics of phenoxymethylpenicillin in the vagina may be explained by the countercurrent vascular system supplying the internal genitalia and upper vagina. The effect of the high concentrations of penicillin on the vaginal microflora is discussed.