Effects of Cyclodextrins and Phospholipids in Enhancing Dissolution of Indomethacin

Phospholipid-based solid drug formulations for oral bioavailability enhancement: A meta-analysis

Low bioavailability nowadays often represents a challenge in oral dosage form development. Solid formulations composed of drug and phospholipid (PL), which, upon contact with water, eventually form multilamellar liposomes (i.e. 'proliposomes'), are an emerging approach to solve such issue. Regarded as an 'improved' version of liposomes concerning storage stability, the potential and versatility of a range of such formulations for oral drug delivery have been extensively discussed. However, a systematic and quantitative analysis of the studies that applied solid PL for oral bioavailability enhancement is currently lacking. Such analysis is necessary for providing an overview of the research progress and addressing the question on how promising this approach can be on bioavailability enhancement. The current review performed a systematic search of references in three evidence-based English databases, Medline, Embase, and SciFinder, from the year of 1985 up till March 2015. A total of 112 research articles and 82 patents that involved solid PL-based formulations were identified. The majority of such formulations was intended for oral drug delivery (55%) and was developed to address low bioavailability issues (49%). A final of 54 studies that applied such formulations for bioavailability enhancement of 43 different drugs with poor water solubility and/or permeability were identified. These proof-of-concept studies with in vitro (n=31) and/or animal (n=23) evidences have been systematically summarized. Meta-analyses were conducted to measure the overall enhancement power (percent increase compared to control group) of solid PL formulations on drugs' solubility, permeability and oral bioavailability, which were found to be 127.4% (95% CI [86.1, 168.7]), 59.6% (95% CI [30.1, 89.0]), and 18.5% (95% CI [10.1, 26.9]) respectively. Correlations between the enhancement factors and in silico physiochemical properties of drugs were also performed to check if such approach can be used to identify the best candidates for oral solid PL formulation. In addition to scientific literature, 13 solid PL formulation-related patents that addressed the issue of low oral bioavailability have been identified and summarized; whereas no clinical study was identified from the current search. By providing systematic information and meta-analysis on studies that applied the principle of 'proliposomes' for oral bioavailability enhancement, the current review should be insightful for formulation scientists who wish to adopt the PL based approach to overcome the solubility, permeability and bioavailability issues of orally delivered drugs.

Quantitative relationship between the chemical structure of antisense nucleosides and their capacity to interact with cyclomalto-octaose

The interaction of twelve 8-substituted-2'-deoxyadenosine and seventeen 5-substituted-2'-deoxyuridine derivatives (antisense nucleosides) with cyclomalto-octaose (GCD) was determined by charge-transfer chromatography and the relative strength of the interaction was calculated. The majority of antisense nucleosides (14 deoxyuridine and 11 deoxyadenosine derivatives) interacted with GCD, which probably led to inclusion complex formation. Stepwise regression analysis proved that the strength of interaction was related to the length of the apolar alkyl chain of substituents and the bulkiness of the nucleoside ring structure. The effect of double or triple bonds in the chain was negligible.

Modification of the apparent lipophilicity of steroidal drugs with gamma-cyclodextrin

The interaction between 17 steroidal drugs and gamma-cyclo-dextrin (gamma-CD) was determined by charge-transfer chromatography and the relative strength of interaction was calculated. The relationship between the strength of interaction and the physico-chemical parameters of steroidal drugs was elucidated with principal component analysis. Gamma-CD interacted with each steroidal drug decreasing the apparent hydrophobicity of the guest molecules. Calculations indicated that the interaction between the drugs and gamma-CD is of mixed character: steric, hydrophobic and electronic forces are involved in the complex formation. The marked influence of gamma-CD on the apparent hydrophobicity of drugs suggests that this interaction may modify the biological properties (absorption, uptake, half-life etc.) of drug-gamma-CD complexes resulting in modified efficacy.

Charge-transfer chromatographic study of the complex formation of some steroidal drugs with carboxymethyl-gamma-cyclodextrin

The interaction between 15 steroidal drugs and carboxymethyl-gamma-cyclodextrin (CM-gamma-CD) was studied by reversed-phase charge-transfer thin-layer chromatography and the relative strength of interaction was calculated. CM-gamma-CD formed inclusion complexes with each compound, the complex always being less hydrophobic than the uncomplexed drug. The inclusion-forming capacity of drugs differed considerably depending on their chemical structures. The linear correlation between the hydrophobicity and specific hydrophobic surface area of anticancer drugs indicated that they can be considered as a homologous series of compounds, although their chemical structures are different. Hydrophobicity of drugs significantly influenced the strength of interaction, indicating the involvement of hydrophobic forces in the binding of drugs to CM-gamma-CD. The marked influence of CM-gamma-CD on the hydrophobicity of drugs suggests that this interaction may modify the biological properties (adsorption, uptake, half-life, etc.) of drug-CM-gamma-CD complexes drug, resulting in modified efficacy.