Fospropofol: pharmacokinetics?

Sir,

We read the article “Fospropofol: Clinical Pharmacology” with great interest.[1] However, we would like to point out that there has been the discussion on pharmacokinetic (P/K) and pharmacodynamic (P/D) properties of fospropofol,[2] which led to the retraction of six studies due to possible errors in propofol assays.[3] This analytical inaccuracy in propofol assay was discovered by the investigators after publication of the data regarding the pharmacokinetic and pharmacodynamic properties of fospropofol and its tolerability.[3]

These studies in phase I or phase II were conducted by MGI Pharma in two independent academic facilities in Europe (Gent, Belgium and Erlangen, Germany). After the detection of the error, MGI Pharma stated that further studies will be conducted within a period of 12 months, and the degree of error will be estimated from the previously published studies.[3] However, the ownership of the drug was transferred from MGI Pharma to Eisai (Woodcliff Lake, NJ). MGI Pharma hence requested the studies to be retracted, as the investigators were unable to conduct new studies within the mentioned time period of 12 months.[4]

The published pharmacokinetic data on fospropofol were derived using an analytical method that has now been shown to be inaccurate; correct pharmacokinetic data are not yet available.[5]