The Dynamic Intestinal Absorption Model (Diamod®), an in vitro tool to study the interconnected kinetics of gastrointestinal solubility, supersaturation, precipitation, and intestinal permeation processes of oral drugs.

This study aimed at developing the Diamod® as a dynamic gastrointestinal transfer model with physically interconnected permeation. The Diamod® was validated by studying the impact of the intraluminal dilution of a cyclodextrin-based itraconazole solution and the negative food effect for indinavir sulfate for which clinical data are available demonstrating that the systemic exposure was strongly mediated by interconnected solubility, precipitation, and permeation processes. The Diamod® accurately simulated the impact of water intake on the gastrointestinal behavior of a Sporanox® solution. Water intake significantly decreased the duodenal solute concentrations of itraconazole as compared to no intake of water. Despite this duodenal behavior the amount of permeated itraconazole was not affected by water intake as observed in vivo. Next to this, the Diamod® accurately simulated the negative food effect for indinavir sulfate. Different fasted and fed state experiments demonstrated that this negative food effect was mediated by an increased stomach pH, entrapment of indinavir in colloidal structures and the slower gastric emptying of indinavir under fed state conditions. Therefore, it can be concluded that the Diamod® is a useful in vitro model to mechanistically study the gastrointestinal performance of drugs.

Desolvation behavior of indinavir sulfate ethanol and follow-up by terahertz spectroscopy.

Active pharmaceutical ingredients are composed of single-component or multicomponent crystals. Multicomponent crystals include salts, co-crystals, and solvates. Indinavir sulfate is the ethanol solvate form of indinavir that is known to deliquesce through moisture absorption. However, the detailed behavior of solvent molecules in the crystal has not been investigated. In this study, we studied the desolvation mechanism of indinavir sulfate ethanol and investigated the behavior of solvent molecules in the solid from. Indinavir sulfate ethanol contained 1.7 molecules of ethanol, 0.7 of which desolvated at room temperature. They were originally two ethanol solvent molecules; one molecule of ethanol desolvated at room temperature, and the conformation of the remaining ethanol and t-butyl groups changed in conjunction with the removal of one ethanol molecule. Desolvation could hardly be detected by powder X-ray diffraction; however, it was detected using terahertz spectroscopy. Terahertz measurement of desolvation showed a high correlation with thermogravimetry data, suggesting that desolvation could be observed non-destructively using terahertz spectroscopy. We concluded that indinavir sulfate 1 ethanol deliquesced at 60% relative humidity, and it turned into an amorphous solid after drying.

Biorelevant dissolution testing of a weak base: Interlaboratory reproducibility and investigation of parameters controlling in vitro precipitation.

Following a previous study which aimed to determine the interlaboratory reproducibility of biorelevant dissolution testing in the USP 2 apparatus for commercial formulations of two weak acids (ibuprofen and zafirlukast), this study attempts to determine the interlaboratory reproducibility using a similar protocol for a commercially available formulation of a weak base, indinavir. Fourteen partners including twelve industrial and two academic partners participated in this study. To ensure uniformity, all partners were provided with a standardized protocol to perform (i) a single medium dissolution test in fasted state simulated gastric and intestinal fluids (FaSSGF and FaSSIF, respectively) and (ii) a two-stage dissolution experiment simulating gastrointestinal transfer. Optionally, partners could run a single-stage dissolution test in fed state simulated intestinal fluid (FeSSIF). For each dissolution test, one Crixivan® capsule (containing 400 mg indinavir as its sulfate salt) was added as dose of interest. For the single medium dissolution test in FaSSIF, all partners observed rapid release of indinavir resulting in supersaturated concentrations, followed by precipitation to equilibrium solubility. The degree and period of supersaturation varied among the participating laboratories. Average dissolution profiles in FeSSIF appeared to be highly reproducible with dissolved concentrations remaining lower than the thermodynamic solubility of indinavir in FeSSIF. For the two-stage dissolution test, most partners observed supersaturated concentrations in the intestinal compartment; two partners observed no supersaturation due to immediate precipitation. Given the fact that a high interlaboratory but low intralaboratory variability was observed when supersaturation/precipitation occurred, an undefined factor was hypothesized as a potential cause of the variability in precipitation. Hence, the impact of several experimental factors on the supersaturation and precipitation behavior of indinavir was investigated in a next step. The investigation indicated that variability is likely attributable to a combination of factors, especially, the time elapsed between sampling and dilution of the sample with the mobile phase. Therefore, when designing a test in which supersaturation and precipitation is anticipated, stringent control of the test methodology, especially regarding sampling and dilution, is needed.

Gastrointestinal dissolution, supersaturation and precipitation of the weak base indinavir in healthy volunteers.

This study investigated the impact of relevant gastrointestinal conditions on the intraluminal dissolution, supersaturation and precipitation behavior of the weakly basic drug indinavir. The influence of (i) concomitant PPI intake and (ii) the nutritional state on the gastrointestinal behavior of indinavir was assessed in order to identify the underlying mechanisms responsible for previously reported interactions. Five healthy volunteers were recruited into a crossover study containing the following arms: fasted state, fed state and fasted state with concomitant proton pump inhibitor (PPI) use. In each condition, one Crixivan® capsule (400mg indinavir) was orally administered with 240mL of water. Gastric and duodenal fluids, aspirated as a function of time, were monitored for total and dissolved indinavir concentrations on a UPLC-MS/MS system. Indinavir's thermodynamic solubility was determined in individual aspirates to evaluate supersaturation. The bioaccessible fraction of indinavir in aspirated duodenal fluids was determined in an ex vivo permeation experiment through an artificial membrane. A nearly complete dissolution of indinavir in the fasted stomach was observed (90±3%). Regardless of dosing conditions, less indinavir was in solution in the duodenum compared to the stomach. Duodenal supersaturation was observed in all three testing conditions. The highest degrees of duodenal supersaturation (6.5±5.9) were observed in the fasted state. Concomitant PPI use resulted in an increased gastric pH and a smaller fraction of indinavir being dissolved (58±24%), eventually resulting in lower intestinal concentrations. In fed state conditions, drug release from the capsule was delayed and more gradually, although a similar fraction of the intragastric indinavir dissolved compared to the fasted state (83±12%). Indinavir was still present in the lumen of the duodenum three hours after oral administration, although it already reached 70% (on average) of the fasted state concentrations (expressed as AUC0-3h). Based on a 2-h permeation experiment, the bioaccessible fraction of indinavir was 2.6-fold lower in a fed state sample compared to a fasted state sample. Our data indicate that the reported reduction in indinavir's bioavailability after concomitant PPI administration is caused by an elevated gastric pH resulting in less indinavir in solution in the stomach and, subsequently, reduced duodenal concentrations. In fed state conditions, however, intestinal micellar entrapment of indinavir appeared to cause the reported reduced bioavailability, regardless of duodenal concentrations.

Cápsulas de sulfato de indinavir: desenvolvimento farmacotécnico-industrial, desenvolvimento do método de dissolução e avaliação / Indinavir sulfate capsules: pharmaceutics-technical-industrial and dissolution method development and evaluation

O sulfato de indinavir é um inibidor da protease no ciclo do vírus da imunodeficiência humana (HIV). O objetivo deste trabalho foi o desenvolvimento da formulação, desenvolvimento e avaliação da metodologia para dissolução, estudo micromerítico, transposição de escala industrial, estudo de estabilidade e estudo comparativo para cápsulas de sulfato de indinavir 500 mg (equivalente a 400 mg de indinavir). Para o desenvolvimento farmacotécnico, realizou-se uma planificação qualitativa de diluentes. As metodologias analíticas para peso médio, desintegração, umidade e uniformidade de peso, seguiram The United States Pharmacopeia 28, enquanto que a metodologia utilizada para dissolução foi desenvolvida e avaliada atendendo à Resolução RE nº 899, de 29 de maio de 2003, da Agência Nacional de Vigilância Sanitária (ANVISA). Os resultados demonstraram que a formulação selecionada correspondeu às especificações de controle físico-químico, além de apresentar viabilidade econômica. Os resultados obtidos com o desenvolvimento e avaliação do método para dissolução mostram que o método atende aos requisitos de Boas Práticas de Fabricação e Controle, pois apresentam a reprodutibilidade, a precisão, a robustez e finalmente a confiabilidade requerida para um método analítico. As cápsulas desenvolvidas de sulfato de indinavir, quando comparadas com o medicamento de referência, são equivalentes entre si, frente a diferentes parâmetros avaliados.

Indinavir sulfate is a protease inhibitor in the cycle of the human immunodeficiency virus (HIV). The purpose of this study was the development of formulation, and its evaluation methodology for dissolution, rheological study, scale transposition, stability study and comparative study for indinavir sulfate 500 mg capsules (equivalent to 400 mg of indinavir). A qualitative design of diluents has been performed for the pharmaceutics development. The analytical methodologies for medium weight, disintegration, humidity and uniformity of weight followed The United States Pharmacopeia 28, while the methodology used for dissolution was developed and evaluated in accordance with Resolution RE nº 899, as of May 29, 2003, issued by the Agência Nacional de Vigilância Sanitária [National Agency for Sanitary Surveillance] (ANVISA). The results have evidenced that the selected formulation corresponds to the specifications of physical-chemical control, besides showing its economic feasibility. The results obtained from the development and evaluation of dissolution method have evidenced that the method complies with the requirements of Good Manufacturing and Control Practices, since it shows the reproducibility, the precision, the robustness and finally the reliability required for an analytical method. The developed indinavir sulfate capsules, when compared with the reference drug, are equivalent, in the light of different evaluated parameters.

Study on the Pharmacokinetics and Bioequivalance of Domestic Indinavir Sulfate in Healthy Chinese Volunteers / 中国药房

0.05)in the main pharmacokinetic parameters between the domestic preparation and the imported preparation,which suggests they are bioequivalent.