We would like to thank Dr Combs and colleagues for their comments regarding our recent article entitled “Prevention of preterm delivery after successful tocolysis in preterm labor by 17 alpha-hydroxyprogesterone caproate: a randomized controlled trial.”

We are happy to clarify that the 17 alpha-hydroxyprogesterone caproate (17P) used in our trial was Progestérone Retard Pharlon licensed by the French Food and Drugs Administration and marketed in France since 1958. The drug is currently manufactured by Bayer Santé, which produces it in Germany in accordance with the detailed guidelines for starting materials established in part II of the European Union Good Manufacturing Practices. The manufacturer of the active substance is included in Bayer Santé’s audit program. Progestérone Retard Pharlon is the only 17P commercially available in France.

Therefore, the absence of significant differences between 17P and control groups in our study cannot be explained by the use of 17P of questionable quality. We are thus confident in our negative conclusion that 17P is not useful after arrested preterm labor.

Finally, it is interesting to note that the same 17P approved by the US Food and Drug Administration and marketed in the United States from 1956 through 2000 under the trade name of Delalutin was withdrawn from the market at the request of the manufacturer for reasons unrelated to safety. Still more interesting is that on Feb. 15, 2011, KV Pharmaceutical announced the price of Makena at $1500 per injection, while the price of Progestérone Retard Pharlon in France is €3.32 per injection.