Examination of lymphatic transport of puerarin in unconscious lymph duct-cannulated rats after administration in microemulsion drug delivery systems

The potential for microemulsion drug delivery systems to improve the lymphatic transport and the portal absorption of a poorly water-soluble drug, puerarin, were investigated in lymph-cannulated rats. SD rats were operated for lymph duct cannulation and were orally dosed with 3 ml puerarin microemulsion (0.6 mg/g, n = 6). The lymph and plasma were collected over 8 h and the concentrations of puerarin and triglyceride were measured. Similarly, control rats (non-lymph-cannulated, n = 6) were dosed orally with puerarin microemulsion and subsequently with puerarin injection intravenously. Plasma and lymph samples were analysed by HPLC. Lymph triglyceride was measured using an enzymatic colorimetric technique. The extent of lymphatic transport via the thoracic duct was 0.06% of the dose for the animals dosed with puerarin microemulsion. The systemic bioavailability of oral puerarin co-administered with lipid was only 16% in the lymph duct-cannulated rats compared with 40% in the controls. These data clearly indicate that the lymphatic transport process contributes significantly to intestinal absorption of puerarin and subsequently to its systemic bioavailability. The results imply that the pharmaceutical scientist may use microemulsion formulations to optimize lymph-targeting drug delivery systems, by improving the extent of lymphatic transport.