Patients are observed for 3 days to establish baseline conditions. They are informed that the treatment period is 21 days during which they receive 15 days of spiramycin and 6 consecutive days of placebo; they are not told which 6-day period they receive placebo. All patients receive 15 days of spiramycin. Patients who do not have a favorable response are treated with a higher dose of spiramycin for an additional 15 days. Responders at either dose are followed weekly for 4 weeks. Should a relapse occur, patients receive an additional 15 days of therapy, at the dose of spiramycin that initially produced a response, following reestablishment of a baseline with 6 days of placebo. Nonresponders to the higher dose are taken off the study.