Effect of pre-incubation with DAPP on P-gp transport of Rhodamine 123 across Caco-2 cell monolayer (basolateral to apical transport) and apparent Permeability Papp. Data represent the average of N = 6 ± SD. *p < 0.025. TEER values were measured before and after the treatment and at the end of the experiment. No changes in TEER values were seen which indicates the integrity of the monolayers. Treatment with DAPP lead to a statistically significant decrease in secretory flux compared with untreated control cells. Treatment with Verapamil represents a positive control for P-gp inhibition.