Concentration of penicillin V in serum and middle ear exudate during treatment of acute otitis media.

Sixty-one patients, aged six months to ten years, with acute purulent otitis media were treated with penicillin V for ten days. The drug was given twice a day in a total daily dose of 50 mg/kg body weight. The concentration of penicillin was determined in serum and in middle ear exudate on one of the first six days of treatment, 60, 120 or 180 minutes after administration of the drug. Bacterial cultures were taken from the nasopharynx before and during treatment and from the middle ear exudate at the time of myringotomy. The serum level of penicillin decreased during treatment. There was also a decrease in penicillin concentration of the middle ear exudate during treatment. This decrease was most pronounced during the first two days. In a few cases Haemophilus influenzae was found in the middle ear exudate during treatment. In these cases the concentration of penicillin in the exudate was found to be higher than the mean concentration at corresponding times. The rapid decrease in the exudate concentration of the drug two to three days after the beginning of therapy may suggest that the patients responded to the treatment and that it is the initial concentration that decides whether an infection will respond to the therapy. High exudate concentrations later on seem to be due mainly to a continuation of the inflammatory reaction and had slight or no clinical effect. Thus, the present investigation produced no strong evidence for a ten-day treatment compared with, for example, a five-day treatment.