In vitro interactions between aged garlic extract and drugs used for the treatment of cardiovascular and diabetic patients

Disease preventing effects gained by garlic consumption have been recognized since early period of history, making commercially available garlic supplements attractive to the general public. Possible pharmacokinetic interactions which could occur between applied drugs and aged garlic extract (AGE) are unknown. To test in vitro impact of some garlic phytochemicals on P-glycoprotein (Pgp), the most recognized efflux transporter, and the effect of AGE on passive membrane permeability, absorptive and secretory intestinal transporters. Rat small intestine and Caco-2 cell monolayers, mounted in side-by-side diffusion chambers were used. Hydrophilic sulphur compounds increased Pgp mediated Rhodamine 123 (Rho123) efflux, whereas the lipophilic ones increased Pgp efflux through rat ileum but not through Caco-2 cell monolayers. Increased activities of secretory (Pgp, multidrug-resistance associated protein 2) and absorptive (monocarboxylate transporter 1, organic anion transporting polypeptide) transporters involved in drug absorption were observed in rat small intestine and Caco-2 cell monolayers in the presence of AGE. Transport of drugs mediated by breast cancer resistance protein and H+-oligopeptide transporter 1 was activated in rat intestine but inhibited through Caco-2 cells. Passive membrane permeability of tested compounds remained unaltered through rat small intestine, while significant changes were observed with Caco-2 cell monolayers. Due to the observed in vitro pharmacokinetic interactions between AGE and investigated cardiovascular, antidiabetic and antiviral drugs, in vivo absorption changes are possible, but the magnitude of change depends on the most profound process involved (influx, efflux, passive diffusion) in compounds permeability.