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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Veterinarian Newsletter March/April 1999 Volume XIV, No II

Since FDA approved Monsanto Company's recombinant bovine somatotropin (rbST) product, Posilac® , in November 1993, FDA and Monsanto have closely monitored the safety and efficacy of Posilac® under commercial use conditions. As expected during a product's life-cycle, the frequency of ADE reports for Posilac® has diminished since initial marketing. The number and nature of the reports raise no new animal health concerns.

The attached table summarizes the important clinical manifestations (CM) from the adverse experience reports possibly related to the use of Posilac®, submitted between February 4, 1994 and February 4, 1996 (first two years of marketing) and between February 4, 1994 and December 31, 1998 (1,235 reports for nearly 5 years of marketing).

Between February 4, 1994 and December 31, 1998, FDA received 1,981 adverse experience reports. 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 1,235 of the 1,981 reports were possibly associated with the use of Posilac® , and that the other 746 reports were not related to treatment with Posilac® .

Of the 1,235 reports possibly related to the use of Posilac® , 276 included reproductive events, 266 included mastitis, 246 involved injection site reactions, 240 included swelling of the udder or abnormal milk, 218 involved increased somatic cell counts, 194 involved digestive disorders, and 159 included foot or leg problems. In some cases, a single report contained multiple conditions.


This summary is intended only as a general reference to the type of reactions that veterinarians and dairy farmers have voluntarily reported. 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 CM
2/4/94 - 2/4/96 (Two years)
Number of Reports with the CM
2/5/94 - 12/31/98 (Almost 5 years)
Reproductive Events*185276
Mastitis (clinical)208266
Injection Site Reactions150246
Other Udder Abnormalities**154240
Increased Somatic Cell Counts in Milk165218
Digestive Disorders***157194
Foot or Leg Problems113159
Cattle Deaths****3039
Cardiovascular Disorders913

* Includes twinning, decreased fertility, abortions, premature births, and retained placentas.
** Includes udder swelling, udder edema, or abnormal milk.
*** Includes anorexia, weight loss, and other digestive tract signs.
**** 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.