Coenzyme Q10 oral bioavailability: effect of formulation type

Coenzyme Q10 (Q10) has a poor bioavailability due to its very low aqueous solubility and high molecular weight. The purpose of this review is to discuss the different types of Q10 drug delivery systems (DDS) ranging from the simple oily dispersions to the nanotechnology-oriented systems such as nanocrystals, self-nanoemulsified drug delivery systems, etc. to overcome the solubility issue. The basics of these approaches were discussed in relationship to the effect of Q10 absorption. For that purpose, the percentage of the drug absorbed to the blood stream out of the administered dose was calculated as the fraction absorbed (Fa%). The Fa% for the nanoemulsions discussed in this article did not correlate with droplet size. In human studies most of the delivery systems had a low Fa% being in the range from 1.53 to 12.48 %. The highest Fa% value was found to be for the self-emulsified drug delivery systems (SEDDS). In dogs studies, the Fa% values ranged between 0.28 (cyclodextrin complex) and 4.8 %. In rat studies, some other DDS like emulsions and solubilized formulations showed Fa% of around 0.22 %. The relationship between the average Fa% in rats, dogs and humans was found to be 1:15:20. One recent study applied both oral and intravenous delivery of Q10; the orally tested SEDDS formulation had an absolute bioavailability of 2.2 % corresponding to Fa% = 0.04 %. The studies with Q10 formulations based only on in vitro data were also discussed and assessed regarding the influence of formulation on solubility, release and/or uptake.