FDA approved Monsanto Company's recombinant bovine somatotropin (rbST) product in November 1993 after a comprehensive review of the product's safety and efficacy, including human food safety. Monsanto's product, known as Posilac®, is the only rbST product approved for increasing milk production in dairy cattle. The product has been commercially available since February 4, 1994.

In a March 14, 1995 FDA TALK PAPER, the Agency stated that during the first year of commercial use a total of 806 adverse effects to the drug were reported to Monsanto and submitted to FDA. The following is an update on the adverse experiences to Posilac® reported to FDA during the next seven months of commercial use; from February 1, 1995 through August 25, 1995. During this period, FDA received 509 adverse experience reports (See table below.) It is important to note that a report of an adverse effect in relation to a drug does not itself establish that the effect was caused by the drug. FDA believes that 392 of the 509 reports were possibly associated with the use of Posilac®, and that the other 117 reports were not related to treatment with Posilac®. Also, all of the reported clinical manifestations are known to occur in dairy cattle not supplemented with Posilac®.

Of the 392 reports possibly related to the use of Posilac®, 100 included reproductive disorders, 77 involved digestive disorders, 69 included mastitis, 62 included injection site reactions, 54 included swelling of the udder or abnormal milk, 53 included foot or leg problems, and 44 involved increased somatic cell counts. In some cases, one report contained more than one condition.

The number and severity of the reported conditions raise no new animal health concerns about the safety of Posilac®. The numbers and types of reactions are similar to those found during clinical trials and indicated on the label. Also, there is no indication that the drug is any less effective than labeled. In addition, FDA and the States have found no indication of a change in the incidence of violative drug residues in milk since Posilac® has been in commercial use.

Based on the these reports of adverse reactions to Posilac®, FDA does not find any cause for concern. However, it is important for dairy farmers to continue to report all adverse reactions associated with the use of rbST. They may report such reactions to Monsanto, to FDA through their veterinarian, or directly to FDA's Center for Veterinary Medicine. CVM accepts collect calls during working hours, and an answering machine is available to record after-hours calls. The telephone numbers are (301) 594-1751 for collect calls during working hours, and (301) 594-0797 to leave a message on evenings and weekends.