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U.S. Department of Health and Human Services

Animal & Veterinary

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Two Year Report On BST

This CVM Update was edited on April 23, 2009 to reflect the sale of POSILAC from Monsanto to Elanco Animal Health, Inc in 2008. Elanco Animal Health is now the company to contact regarding adverse events associated with the use of POSILAC.  Also, the phone number for reporting adverse events to CVM has been updated.


May 16, 1996

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

During the first year of commercial use of Posilac®, a total of 806 reports of adverse effects were reported to Monsanto and submitted to FDA.

The following is a 24-month summary of the adverse experiences to Posilac® reported to FDA from February 4, 1994 through February 4, 1996. During this period, FDA received 1438 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 918 of the 1438 reports were possibly associated with the use of Posilac®, and that the other 520 reports were not related to treatment with Posilac®. Also, the reported clinical manifestations are known to occur in dairy cattle not supplemented with Posilac®.

Of the 918 reports possibly related to the use of Posilac®, 208 included mastitis, 185 included reproductive events, 165 involved increased somatic cell counts, 157 involved digestive disorders, 154 included swelling of the udder or abnormal milk, 150 included injection site reactions, and 113 included foot or leg problems. In some cases, a single report contained multiple conditions.

The number and severity of the reported conditions will be the subject of a May 29,1996, Veterinary Medicine Advisory Committee (VMAC) meeting. The VMAC will consider the need for label revisions to better characterize reported signs that are possibly associated with the use of Posilac®.

FDA encourages dairy farmers and veterinarians to report all adverse reactions associated with the use of rbST. They may report such reactions to Elanco Animal Health, Inc., the current owner of Posilac®, to FDA through their veterinarian, or directly to FDA's Center for Veterinary Medicine at 1-888-FDA-VETS. 


The following table summarizes the important clinical manifestations (CM) from the 918 adverse experience reports possibly related to the use of Posilac® from February 4, 1994 through February 4, 1996.

This summary is intended only as a general reference to the type of reactions that veterinarians and dairy farmers have voluntarily reported to the manufacturer or FDA. Therefore, the summary is not by itself a basis for determining drug association for a particular sign, safety or efficacy of the drug, or determining the frequency or incidence rate of a clinical manifestation. Each of the reports may contain one or more CMs, and as a result the number of CMs exceeds the number of reports. The reported clinical manifestations are known to occur in dairy cattle not supplemented with Posilac®.

Clinical Manifestation (CM)Number of Reports with the CMEstimated Number of Cows Reported with the CM
Mastitis (clinical)2084348
Reproductive Events*1854172
Increased Somatic Cell Counts in Milk1654576
Digestive Disorders**1574836
Other Udder Abnormalities***1542236
Injection Site Reactions1501946
Foot or Leg Problems1132307
Cattle Deaths****3063
Cardiovascular Disorders930
*Includes twinning, decreased fertility, abortions, premature births, and retained placentas.
**Includes anorexia, weight loss, and other digestive tract signs.
***Includes udder swelling, udder edema, or abnormal milk.
****The most commonly reported CM for all other dairy cattle drug products is death. This includes cows that were euthanized or slaughtered due to an illness, such as chronic mastitis.

Contact FDA

240-276-9115 FAX
Issued by: FDA, Center for Veterinary Medicine

Communications Staff, HFV-12

7519 Standish Place

Rockville, MD 20855