Stability and bioequivalence studies of two marketed formulations of coenzyme Q(10) in beagle dogs

Coenzyme Q(10) (CoQ(10)), a highly lipophilic compound present in the inner mitochondrial membrane, is essential for production of cellular energy in the form of ATP. CoQ(10) is used as an antioxidant and also in the treatmen t of various cardiovascular disorders. The relative bioavailabilities of po wder filled capsule (I) and oil-based formulation (II) of CoQ(10) were comp ared in beagle dogs in an open, randomized, multiple dose, cross-over desig n. Poor and slow absorption characteristics were observed for both the form ulations. The AUC, C-max, and T-max for formulation I and II are comparable (p<0.05) where the values for formulation I are 22.84+/-6.3 mu g ml(-1) h, 0.51+/0.11 mu g/ml, and 6.1+/-2.0 h whereas the values for formulation II are 24.32+/-5.6 mu g ml(-1) h, 0.55+/-0.16 mu g/ml, and 6.6+/-2.3 h, respec tively. Stability of CoQ(10) at various temperature and humidity conditions and its photostability were studied, Various antioxidants were evaluated t o determine the type and amount of antioxidant(s) required to improve the s tability of CoQ(10). Large extent of degradation was observed at 45 degrees C and 55 degrees C. The effect of humidity conditions on degradation was i nsignificant. Among the various antioxidants studied, mixture of ascorbic a cid (5%) and EDTA (0.1%) offered better protection than phenolic antioxidan ts such as butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT) , or propyl gallate (PG). Further, increasing concentrations of phenolic an tioxidants (from 0.1 to 0.3%) accelerated the degradation.