First Metformin Study Shows Drug Has “Prolonged Detection Time”

[Wandering Eyes]

All this week, the TDN has been trying to nail down concrete details surrounding the studies performed for the Racing Medication & Testing Consortium's (RMTC) Scientific Advisory Committee (SAC) into the way metformin behaves in Thoroughbreds.

It turns out that the first of the three papers stemming from this study was published Wednesday in the online journal, Drug Testing and Analysis. In short, the study finds a “prolonged detection time” for the drug.

This first study involved 12 Thoroughbreds aged between two and seven years of age. It was broken into two phases.

In phase one, six of these horses were given an oral administration of 15 grams of metformin, while the other six were given an intravenous administration of 5 milligrams per kilogram of metformin.

When metformin was no longer detectable in the blood and urine of these 12 horses, phase two began, which saw the horses given opposite treatments.

It took 21 days for the metformin to fall below the limit of quantification (LOQ), set at 0.25?ng/mL for all 12 horses given both the intravenous and oral administrations.

It took 11 days post-administration for the metformin concentrations to fall below the 0.25?ng/mL level in six of the 12 horses.

The maximum concentration of metformin detected in this study was 941 nanograms per milliliter at around the 51 minute mark.

The paper also points out that Metformin concentrations in urine “fluctuated significantly” between and within individual horses, “and there was not a consistent relationship between blood and urine samples across time points.”

Interestingly, the study points out that following oral administration of the drug, “five horses showed mild signs of abdominal discomfort, such as pawing and rolling 4?[hours] after the drug was administered; these signs resolved on their own within 2?[hours].”

Starting in June of last year, the RMTC performed an initial review of the existing scientific literature on the drug, then gathered together a team of researchers who performed a three-part study.

The result was a recommended Minimum Reporting Level (MRL) of 4.0 nanograms per milliliter in blood. Because of metformin's erratic elimination behavior in urine, the researchers haven't recommend using it as a suitable testing matrix.

Prior to that, federal regulators had used a much lower screening limit of 0.5 nanograms per milliliter in blood and 1 nanogram per milliliter in urine. And prior to that, they had used an approach allowing each individual lab's limit of detection which varied from facility to facility.

Two more papers are being submitted for publication. And how much did this whole endeavour cost? That's currently unclear.

When asked, a Horseracing Integrity and Welfare Unit (HIWU) spokesperson wrote the following:

“The cost of the metformin studies was covered as part of the pre-established annual laboratory credit with UC Davis for science and research that is applied to California's assessment for HISA. This is determined by HISA, HIWU, UC Davis, and the CHRB. HISA and HIWU did not contribute additional funding beyond the established credit.

“The credits enable Program laboratories–in this case, UC Davis–to perform timely and relevant research on behalf of the ADMC Program on an ongoing basis. These costs fall under the “Lab Testing” portion of HISA's budget, which covers all of the Program laboratories.”

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