Quantitative Prediction of Oral Bioavailability of a Lipophilic Antineoplastic Drug Bexarotene Administered in Lipidic Formulation Using a Combined In Vitro Lipolysis/Microsomal Metabolism Approach

Inclusion of Medium-Chain Triglyceride in Lipid-Based Formulation of Cannabidiol Facilitates Micellar Solubilization In Vitro, but In Vivo Performance Remains Superior with Pure Sesame Oil Vehicle

Oral sesame oil-based formulation facilitates the delivery of poorly water-soluble drug cannabidiol (CBD) to the lymphatic system and blood circulation. However, this natural oil-based formulation also leads to considerable variability in absorption of CBD. In this work, the performance of lipid-based formulations with the addition of medium-chain triglyceride (MCT) or surfactants to the sesame oil vehicle has been tested in vitro and in vivo using CBD as a model drug. The in vitro lipolysis has shown that addition of the MCT leads to a higher distribution of CBD into the micellar phase. Further addition of surfactants to MCT-containing formulations did not improve distribution of the drug into the micellar phase. In vivo, formulations containing MCT led to lower or similar concentrations of CBD in serum, lymph and MLNs, but with reduced variability. MCT improves the emulsification and micellar solubilization of CBD, but surfactants did not facilitate further the rate and extent of lipolysis. Even though addition of MCT reduces the variability, the in vivo performance for the extent of both lymphatic transport and systemic bioavailability remains superior with a pure natural oil vehicle.

A Novel Co-Crystal of Bexarotene and Ligustrazine Improves Pharmacokinetics and Tissue Distribution of Bexarotene in SD Rats

Bexarotene (BEX), a specific retinoic acid X receptor (RXR) agonist granted by Food and Drug Administration (FDA) approval for the clinical treatment of T cell lymphoma, has now been found to exert pharmacological effects in the nervous system, with low bioavailability and poor cerebral distribution limiting its application in treatment on neurological disorders. Pharmaceutical co-crystal was a helpful method to improve the bioavailability and tissue distribution of active pharmaceutical ingredients (APIs). Here, 2bexarotene-ligustrazine (2BEX-LIG), a novel co-crystal system of BEX and ligustrazine (LIG) of which with BEX is an API, was constructed with satisfactory stability and enhanced solubility. The pharmacokinetics characteristics of BEX were detected, and the results showed that the absolute bioavailability and the cerebral concentration of BEX in rats administrated with 2BEX-LIG were enhanced from 22.89% to 42.86% and increased by 3.4-fold, respectively, compared with those in rats administrated an equivalent of BEX. Hence, our present study indicated that the novel co-crystal of 2BEX-LIG contributed to improving BEX oral bioavailability and cerebral distribution, thereby providing significant advantages for clinical application of brain tumors and other neurological diseases.

Lymphatic Transport of Drugs after Intestinal Absorption: Impact of Drug Formulation and Physicochemical Properties

PURPOSE

To provide a comprehensive and up-to-date overview focusing on the extent of lymphatic transport of drugs following intestinal absorption and to summarize available data on the impact of molecular weight, lipophilicity, formulation and prandial state.

METHODS

Literature was searched for in vivo studies quantifying extent of lymphatic transport of drugs after enteral dosing. Pharmacokinetic data were extracted and summarized. Influence of molecular weight, log P, formulation and prandial state was analyzed using relative bioavailability via lymph (F_RL) as the parameter for comparison. The methods and animal models used in the studies were also summarized.

RESULTS

Pharmacokinetic data on lymphatic transport were available for 103 drugs. Significantly higher F_RL [median (IQR)] was observed in advanced lipid based formulations [54.4% (52.0)] and oil solutions [38.9% (60.8)] compared to simple formulations [2.0% (27.1)], p < 0.0001 and p = 0.004, respectively. Advanced lipid based formulations also provided substantial F_RL in drugs with log P < 5, which was not observed in simple formulations and oil solutions. No relation was found between F_RL and molecular weight. There were 10 distinct methods used for in vivo testing of lymphatic transport after intestinal absorption so far.

CONCLUSION

Advanced lipid based formulations provide superior ability to increase lymphatic absorption in drugs of various molecular weights and in drugs with moderate to low lipophilicity.

A novel nucleoside rescue metabolic pathway may be responsible for therapeutic effect of orally administered cordycepin

Although adenosine and its analogues have been assessed in the past as potential drug candidates due to the important role of adenosine in physiology, only little is known about their absorption following oral administration. In this work, we have studied the oral absorption and disposition pathways of cordycepin, an adenosine analogue. In vitro biopharmaceutical properties and in vivo oral absorption and disposition of cordycepin were assessed in rats. Despite the fact that numerous studies showed efficacy following oral dosing of cordycepin, we found that intact cordycepin was not absorbed following oral administration to rats. However, 3′-deoxyinosine, a metabolite of cordycepin previously considered to be inactive, was absorbed into the systemic blood circulation. Further investigation was performed to study the conversion of 3′-deoxyinosine to cordycepin 5′-triphosphate in vitro using macrophage-like RAW264.7 cells. It demonstrated that cordycepin 5′-triphosphate, the active metabolite of cordycepin, can be formed not only from cordycepin, but also from 3′-deoxyinosine. The novel nucleoside rescue metabolic pathway proposed in this study could be responsible for therapeutic effects of adenosine and other analogues of adenosine following oral administration. These findings may have importance in understanding the physiology and pathophysiology associated with adenosine, as well as drug discovery and development utilising adenosine analogues.