Is there a fast track ("Darmstrasse") for fluids in the small intestine? Evidence from magnetic resonance imaging

BACKGROUND

The transit and distribution pattern of fluids in the small intestine is a key parameter for the dissolution and absorption of drugs. Although some information is known about the small intestinal water content after administration of fluid volumes and meals, the intestinal transit of orally ingested fluids and solutions has been barely investigated. The aim of this three-arm, cross-over, 9-subject human study was to investigate the transit of orally ingested water in the small intestine under fasting and postprandial conditions using MRI. To identify the ingested water, manganese gluconate, which can be identified with T1-weighted MRI sequences, was added as a marker. Using Horos (DICOM software), quantification of the distribution of Mn2+ ions in the gastrointestinal tract in fasted versus fed state (standard meal by FDA guidance and a light meal) was possible. The distribution and approximate wetted intestinal length was very similar in the fasting and postprandial states, suggesting rapid transport of water ingested after a meal through the chyme-filled small intestine in continuation of the "Magenstrasse" (stomach road). In some subjects, manganese gluconate reached deeper parts of the small intestine even more quickly in the postprandial state than in the fasting arm of the study. A deeper understanding of the behaviour of solutes in the gastrointestinal tract is fundamental to a mechanistic explanation for the kinetic interaction between food and drug intake (food effects).

Assessment of food effects during clinical development

Food-drug interactions frequently hamper oral drug development due to various physicochemical, physiological and formulation-dependent mechanisms. This has stimulated the development of a range of promising biopharmaceutical assessment tools which, however, lack standardized settings and protocols. Hence, this manuscript aims to provide an overview of the general approach and the methodology used in food effect assessment and prediction. For in vitro dissolution-based predictions, the expected food effect mechanism should be carefully considered when selecting the level of complexity of the model, together with its drawbacks and advantages. Typically, in vitro dissolution profiles are then incorporated into physiologically based pharmacokinetic models, which can estimate the impact of food-drug interactions on bioavailability within 2-fold prediction error, at least. Positive food effects related to drug solubilization in the GI tract are easier to predict than negative food effects. Preclinical animal models also provide a good level of food effect prediction, with beagle dogs remaining the gold standard. When solubility-related food-drug interactions have large clinical impact, advanced formulation approaches can be used to improve fasted state pharmacokinetics, hence decreasing the fasted/fed difference in oral bioavailability. Finally, the knowledge from all studies should be combined to secure regulatory approval of the labelling instructions.

Fasted and fed state human duodenal fluids: Characterization, drug solubility, and comparison to simulated fluids and with human bioavailability

Accurate in vivo predictions of intestinal absorption of low solubility drugs require knowing their solubility in physiologically relevant dissolution media. Aspirated human intestinal fluids (HIF) are the gold standard, followed by simulated intestinal HIF in the fasted and fed state (FaSSIF/FeSSIF). However, current HIF characterization data vary, and there is also some controversy regarding the accuracy of FaSSIF and FeSSIF for predicting drug solubility in HIF. This study aimed at characterizing fasted and fed state duodenal HIF from 16 human volunteers with respect to pH, buffer capacity, osmolarity, surface tension, as well as protein, phospholipid, and bile salt content. The fasted and fed state HIF samples were further used to investigate the equilibrium solubility of 17 representative low-solubility small-molecule drugs, six of which were confidential industry compounds and 11 were known and characterized regarding chemical diversity. These solubility values were then compared to reported solubility values in fasted and fed state HIF, FaSSIF and FeSSIF, as well as with their human bioavailability for both states. The HIF compositions corresponded well to previously reported values and current FaSSIF and FeSSIF compositions. The drug solubility values in HIF (both fasted and fed states) were also well in line with reported solubility data for HIF, as well as simulated FaSSIF and FeSSIF. This indicates that the in vivo conditions in the proximal small intestine are well represented by simulated intestinal fluids in both composition and drug equilibrium solubility. However, increased drug solubility in the fed vs. fasted states in HIF did not correlate with the human bioavailability changes of the same drugs following oral administration in either state.

Nanoformulation strategies for improving intestinal permeability of drugs: A more precise look at permeability assessment methods and pharmacokinetic properties changes

The therapeutic efficacy of orally administered drugs is often restricted by their inherent limited oral bioavailability. Low water solubility, limited permeability through the intestinal barrier, instability in harsh environment of the gastrointestinal (GI) tract and being substrate of the efflux pumps and the cytochrome P450 (CYP) can impair oral drug bioavailability resulting in erratic and variable plasma drug profile. As more drugs with low membrane permeability are developed, new interest is growing to enhance their intestinal permeability and bioavailability. A wide variety of nanosystems have been developed to improve drug transport and absorption. Sufficient evidence exists to suggest that nanoparticles are able to increase the transepithelial transport of drug molecules. However, key questions remained unanswered. What types of nanoparticles are more efficient? What are preclinical (or clinical) achievements of each type of nanoformulation in terms of pharmacokinetic (PK) parameters? Addressing this issue in this paper, we have reviewed the current literature regarding permeability enhancement, permeability assessment methods and changes in PK parameters following administration of various nanoformulations. Although permeability enhancement by various nanoformulations holds great promise for oral drug delivery, many challenges still need to be addressed before development of more clinically successful nanoproducts.

Relative bioavailability of an extemporaneously prepared aprepitant oral suspension in healthy adults

Purpose

Use of aprepitant for chemotherapy-induced nausea and vomiting prophylaxis in patients unable to swallow capsules is hindered by the lack of a commercially available oral liquid formulation in many jurisdictions. A stable oral suspension can be extemporaneously prepared using commercially available capsules. We aimed to determine the bioavailability of this aprepitant suspension relative to the capsule.

Methods

This two-period crossover study enrolled 17 healthy adult volunteers. Volunteers received a single 125 mg aprepitant dose during each study period. Order of formulation presentation (capsule vs suspension first) was randomized. Thirteen blood samples were collected over a 48-h period. Aprepitant plasma concentrations were determined using liquid chromatography-mass spectroscopy. Relative bioavailability was defined as the geometric least squares mean ratio for area under the concentration versus time curve (AUC) from time zero to infinity of the aprepitant suspension versus the capsule. Bioequivalence, defined as per Health Canada guidelines, was assessed as a secondary aim.

Results

Relative bioavailability of the aprepitant suspension was 82.3% (90% CI: 69.09-98.00%). Bioequivalence was not established: geometric least squares mean ratios (suspension/capsule) for AUC time zero to 48 h and maximum concentration were 87.8% (90% CI: 75.48–102.16%) and 86.1% (90% CI: 75.59–98.16%), respectively. No serious adverse events were observed.

Conclusions

With a relative bioavailability of 82.3%, the extemporaneous aprepitant oral suspension was well-absorbed relative to the capsule. Though not bioequivalent to the oral capsule, the clinical use of this aprepitant oral suspension in adult and pediatric patients unable to swallow capsules is likely to be effective and safe.

Neurokinin 1 receptor antagonists in the prevention of chemotherapy-induced nausea and vomiting: focus on fosaprepitant

Chemotherapy-induced nausea and vomiting (CINV) remains a challenge in cancer care. Improved understanding of CINV pathophysiology has triggered the development of new antiemetic therapeutic options, such as selective neurokinin-1 (NK₁) receptor antagonists (RAs), which effectively prevent CINV when added to a standard antiemetic regimen (serotonin-3 RA and dexamethasone). Aprepitant and its water-soluble prodrug, fosaprepitant dimeglumine, are the most widely used NK₁ RAs, with extensive clinical use worldwide. Recently, a Phase III trial prospectively evaluated fosaprepitant-based antiemetic therapy for CINV prevention in a large, well-defined nonanthracycline- and cyclophosphamide-based moderately emetogenic chemotherapy population. Fosaprepitant demonstrated significantly improved efficacy outcomes compared with a control regimen and was generally well tolerated, indicating that NK₁ RAs are a valuable therapeutic option in this setting.

Fosaprepitant Dimeglumine: A Review in the Prevention of Nausea and Vomiting Associated with Chemotherapy

Intravenous fosaprepitant dimeglumine (Emend(®) for injection, IVEmend(®); henceforth referred to as fosaprepitant) is a prodrug of and is rapidly converted to the antiemetic aprepitant, and is approved in several countries worldwide (as part of an antiemetic regimen) for the prevention of nausea and vomiting associated with highly and moderately emetogenic chemotherapy (HEC and MEC). This narrative review discusses the pharmacological properties of intravenous fosaprepitant and its clinical efficacy and tolerability in the prevention of nausea and vomiting associated with HEC and MEC. In large, randomized phase III clinical trials, a single intravenous dose of fosaprepitant 150 mg was an effective and generally well tolerated addition to an antiemetic regimen that included dexamethasone and a serotonin 5-HT3 receptor antagonist in adult cancer patients undergoing treatment with HEC or MEC. It was also noninferior to an oral aprepitant-based regimen in adult cancer patients undergoing HEC treatment. The tolerability profile of a fosaprepitant-based regimen was typical of that in patients receiving emetogenic chemotherapy, and adverse events were generally consistent with those observed with an aprepitant-based regimen. Fosaprepitant provides a useful addition to antiemetic therapy regimens.

Differential clinical pharmacology of rolapitant in delayed chemotherapy-induced nausea and vomiting (CINV)

Rolapitant is a highly selective neurokinin-1 receptor antagonist, orally administered for a single dose of 180 mg before chemotherapy with granisetron D1, dexamethasone 8 mg BID on day 2-4. It has a unique pharmacological characteristic of a long plasma half-life (between 163 and 183 hours); this long half-life makes a single use sufficient to cover the delayed emesis risk period. No major drug-drug interactions between rolapitant and dexamethasone or other cytochrome P450 inducers or inhibitors were observed. The clinical efficacy of rolapitant was studied in two phase III trials in highly emetogenic chemotherapy and in one clinical trial in moderately emetogenic chemotherapy. The primary endpoint was the proportion of patients achieving a complete response (defined as no emesis or use of rescue medication) in the delayed phase (>24-120 hours after chemotherapy). In comparison to granisetron (10 μg/kg intravenously) and dexamethasone (20 mg orally) on day 1, and dexamethasone (8 mg orally) twice daily on days 2-4 and placebo, rolapitant showed superior efficacy in the control of delayed and overall emesis. This review aims at revising the pharmacological characteristics of rolapitant, offering an updated review of the available clinical efficacy and safety data of rolapitant in different clinical settings, highlighting the place of rolapitant in the management of chemotherapy-induced nausea and vomiting (CINV) among currently available guidelines, and exploring the future directions of CINV management.

A randomized trial of olanzapine versus palonosetron versus infused ondansetron for the treatment of breakthrough chemotherapy-induced nausea and vomiting in patients undergoing hematopoietic stem cell transplantation

PURPOSE

The primary aim of this study was to compare the effectiveness of olanzapine, palonosetron and ondansetron infusion (standard of care) for the treatment of breakthrough chemotherapy-induced nausea and vomiting (CINV) in patients undergoing hematopoietic stem cell transplantation (HSCT).

METHOD

It was a randomized open-label prospective study. Sixty-two patients were randomized to receive either ondansetron 32-mg infusion over 24 h, or olanzapine wafer 10 mg once daily in addition to ondansetron 8 mg IV three times a day or a single dose of palonosetron 0.25 mg IV instead of ondansetron. All groups were allowed rescue antiemetics. The primary endpoint was a composite outcome of no emesis, no use of rescue medication, and nausea score reduction of ≥50 %. The secondary endpoint was nausea score reduction of ≥50 %. Both endpoints were measured at 24 and 48 h after initiation of the study treatment. Statistical analysis was conducted using a double-sided Fisher's exact test.

RESULT

The primary endpoint was achieved in 6, 45, and 18 %, and 6, 64, and 18 % of ondansetron versus olanzapine versus palonosetron patient groups at 24 and 48 h, respectively. The secondary outcome was observed in 17, 60, and 62 %, and 35, 71, and 43 % of ondansetron versus olanzapine versus palonosetron patient groups at 24 and 48 h, respectively. Serious adverse drug reactions were not reported in any arms. Time to engraftment was not significantly different between the arms.

CONCLUSIONS

Olanzapine was an effective treatment of breakthrough CINV. A single dose of palonosetron significantly reduced nausea up to 24 h.