Tishcon Letter Addresses CoQ10 Study Shortcomings
WESTBURY, N.Y.Raj Chopra, president of Tishcon Corp., wrote a letter to the editor of the International Journal of Clinical Pharmacology and Therapeutics in response to a study the journal published about coenzyme Q10 (CoQ10). The letter was published in the June 2003 issue (41, 6:275, 2003), and is reprinted here.
Sir - There are several major shortcomings in the recent paper by Joshi et al entitled Comparative bioavailability of two novel coenzyme Q10 preparations in humans (Int J Clin Pharmacol Ther 2003, 41:42-48).
1. This was a two-part study, the first a four-arm single-dose crossover study with 24 subjects evaluating the oral bioavailability of four coenzyme Q10 formulations, and the second, a single-arm singledose study with a fifth formulation in a different group of six subjects. This design makes any comparison of the results between two studies invalid and meaningless.
2. The baseline values for plasma coenzyme Q10 (0.21-0.25 mcg/ml) are extremely low and such low values have not been reported in the literature for healthy subjects [Chopra et al. 1998, Kaikkonen et al. 1997, Miles et al. 2002, Tang et al. 2001]. If this is not due to methodology problems here, these values in fact reflect a pathologic condition.
3. Likewise, the Tmax and t1/2 for all the five formulations (1.3-4.1 and 4.1-5.8 h, respectively) are much lower than reported values. The t1/2 values are exceptionally low. The literature values range from six to eight hours for Tmax and about 33 hours for t1/2 [Miles et al. 2002, Tomono et al. 1986]. The authors do not appear to be familiar with the published literature in this area.
4. There is some discrepancy in the AUC data. While the blood samples were drawn for 12 hours after dosing, AUCs reported are for 0-20 h in both Tables 1 and 2.
5. Calculation of the elimination half-life values from the 12 h data is not valid considering that the reported half-life for coenzyme Q10 is about 33 hours.
6. The AUC data (Table 1) does not show any significant difference between the 4 products in Study 1 and this clearly implies that there would be no differences in their clinical effects. This being the case, differences in Tmax values cannot be expected to confer any advantage for the product with a shorter Tmax, namely the fast melting formulation.
In summary, this is a poorly designed study that lacks in scientific rigor and utility. The primary purpose of the study appears to be the promotion of a particular product. While not adding anything new, it could create confusion particularly with respect to the interpretation of pharmacokinetic data as applied to dietary supplements.
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