The impact of lymphatic transport on the systemic disposition of lipophilic drugs

This work investigates the influence of drug absorption route (intestinal lymphatics vs. blood supply) on drug pharmacokinetics and tissue distribution. To achieve this aim, the pharmacokinetics and tissue distribution of model compounds [1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane, DDT; halofantrine] and lipids were assessed following intravenous delivery in lymph lipoproteins or plasma, and were found to differ significantly. For DDT, the clearance (CL) and volume of distribution (V_d) were higher, whereas for halofantrine, CL and V_d were lower, after entry in lymph versus plasma due, in particular, to differences in adipose tissue and liver uptake. In a recent study, halofantrine CL and V_d were similar following entry in lymph or entry in plasma into the systemic circulation of animals predosed with lymph, whereas in the current study, predosing lymph did not influence DDT CL and V_d. For compounds such as DDT, changes to the route of absorption may thus directly impact on pharmacokinetics and tissue distribution, whereas for halofantrine factors that influence lymphatic transport may, by altering systemic lipoprotein concentrations, indirectly impact pharmacokinetics and tissue distribution. Ultimately, careful control of dosing conditions (formulation, prandial state), and thus the extent of lymphatic transport, may be important in assuring reproducible efficacy and toxicity for lymphatically transported drugs.