The oral administration of bromocriptine induces a variety of side-effects in about 50-70% of patients, the most common being nausea and vomiting, probably related to the local gastrointestinal effect of the drug. Nasal administration makes it possible to avoid intestinal and liver metabolism. This study compared the serum concentrations of bromocriptine and prolactin (PRL) in twenty puerperal women who had asked to discontinue breast feeding and were randomized to receive a single oral (2.5 mg) or nasal spray dose (0.8 mg) of bromocriptine. Serum bromocriptine and PRL concentrations were measured at various times before and after drug administration. At 15 min, the circulating concentrations of bromocriptine were about eight times higher after nasal than after oral administration; peak serum concentration (CMax) was reached respectively 45 min and 60 min after administration, and was about three times higher after nasal administration (314 +/- 102 pg/ml vs 112.30 +/- 34.47 pg/ml). The reduction in serum PRL concentrations was also more rapid in the nasally-treated group reaching the normal assay range of < 20 micrograms/l within two as against five hours post-administration. Four orally-treated patients complained of nausea; in the nasally-treated group, six patients reported only a mild endonasal burning that disappeared within a few minutes of administration. Our results suggest that the nasal administration of bromocriptine may lead to a reduction in the required overall dose and fewer gastrointestinal side-effects, and may therefore improve therapy compliance.