Simulation of gastric lipolysis and prediction of felodipine release from a matrix tablet in the fed stomach

Opportunities for milk and milk-related systems as 'new' low-cost excipient drug delivery materials

Milk is well recognised as an amazing delivery system for essential lipids, poorly soluble nutrients, sugars, amino acids and delivery of critical biological molecules to sustain the infant and adult alike. It is also a safe and abundant resource with potential to act as a low-cost material for formulation of medicines, especially for paediatric patients and those in low economy settings. However, its use in low cost formulations has never developed beyond preclinical evaluation. Reasons for this are several-fold including variable composition and therefore regulatory challenges, as well as a lack of clear understanding around when milk or milk-related materials like infant formula could best be deployed by linking drug properties with excipient composition attributes, especially when taking digestion into account. This review collects the current understanding around these issues. It is apparent from the evolving understanding that while milk may be a bridge too far for translation as an excipient, infant formula is positioned to play a key role in the future because, as a powder-based excipient, it has the performance benefits of milk powder together with the controlled specifications during manufacture and versatility of application to function as a low cost lipid excipient to enable potential translation for the oral delivery of poorly water soluble drugs for key populations including paediatrics and low economy medicines.

Development and Bio-Predictive Evaluation of Biopharmaceutical Properties of Sustained-Release Tablets with a Novel GPR40 Agonist for a First-in-Human Clinical Trial

Sustained-release (SR) formulations may appear advantageous in first-in-human (FIH) study of innovative medicines. The newly developed SR matrix tablets require prolonged maintenance of API concentration in plasma and should be reliably assessed for the risk of uncontrolled release of the drug. In the present study, we describe the development of a robust SR matrix tablet with a novel G-protein-coupled receptor 40 (GPR40) agonist for first-in-human studies and introduce a general workflow for the successful development of SR formulations for innovative APIs. The hydrophilic matrix tablets containing the labeled API dose of 5, 30, or 120 mg were evaluated with several methods: standard USP II dissolution, bio-predictive dissolution tests, and the texture and matrix formation analysis. The standard dissolution tests allowed preselection of the prototypes with the targeted dissolution rate, while the subsequent studies in physiologically relevant conditions revealed unwanted and potentially harmful effects, such as dose dumping under an increased mechanical agitation. The developed formulations were exceptionally robust toward the mechanical and physicochemical conditions of the bio-predictive tests and assured a comparable drug delivery rate regardless of the prandial state and dose labeled. In conclusion, the introduced development strategy, when implemented into the development cycle of SR formulations with innovative APIs, may allow not only to reduce the risk of formulation-related failure of phase I clinical trial but also effectively and timely provide safe and reliable medicines for patients in the trial and their further therapy.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Impact of gastrointestinal tract variability on oral drug absorption and pharmacokinetics: An UNGAP review

The absorption of oral drugs is frequently plagued by significant variability with potentially serious therapeutic consequences. The source of variability can be traced back to interindividual variability in physiology, differences in special populations (age- and disease-dependent), drug and formulation properties, or food-drug interactions. Clinical evidence for the impact of some of these factors on drug pharmacokinetic variability is mounting: e.g. gastric pH and emptying time, small intestinal fluid properties, differences in pediatrics and the elderly, and surgical changes in gastrointestinal anatomy. However, the link of colonic factors variability (transit time, fluid composition, microbiome), sex differences (male vs. female) and gut-related diseases (chronic constipation, anorexia and cachexia) to drug absorption variability has not been firmly established yet. At the same time, a way to decrease oral drug pharmacokinetic variability is provided by the pharmaceutical industry: clinical evidence suggests that formulation approaches employed during drug development can decrease the variability in oral exposure. This review outlines the main drivers of oral drug exposure variability and potential approaches to overcome them, while highlighting existing knowledge gaps and guiding future studies in this area.

Solid Lipid Microparticles for Oral Delivery of Catalase: Focus on the Protein Structural Integrity and Gastric Protection

Protein inactivation either during the production process or along the gastrointestinal tract is the major problem associated with the development of oral delivery systems for biological drugs. This work presents an evaluation of the structural integrity and the biological activity of a model protein, catalase, after its encapsulation in glyceryl trimyristate-based solid lipid microparticles (SLMs) obtained by the spray congealing technology. Circular dichroism and fluorescence spectroscopies were used to assess the integrity of catalase released from SLMs. The results confirmed that no conformational change occurred during the production process and both the secondary and tertiary structures were retained. Catalase is highly sensitive to temperature and undergoes denaturation above 60 °C; nevertheless, spray congealing allowed the retention of most biological activity due to the loading of the drug at the solid state, markedly reducing the risk of denaturation. Catalase activity after exposure to simulated gastric conditions (considering both acidic pH and the presence of gastric digestive hydrolases) ranged from 35 to 95% depending on the carrier: increasing of both the fatty acid chain length and the degree of substitution of the glyceride enhanced residual enzyme activity. SLMs allowed the protein release in a simulated intestinal environment and were not cytotoxic against HT29 cells. In conclusion, the encapsulation of proteins into SLMs by spray congealing might be a promising strategy for the formulation of nontoxic and inexpensive oral biotherapeutic products.

Physiological Considerations and In Vitro Strategies for Evaluating the Influence of Food on Drug Release from Extended-Release Formulations

Food effects on oral drug bioavailability are a consequence of the complex interplay between drug, formulation and human gastrointestinal (GI) physiology. Accordingly, the prediction of the direction and the extent of food effects is often difficult. With respect to novel formulations, biorelevant in vitro methods can be extremely powerful tools to simulate the effect of food-induced changes on the physiological GI conditions on drug release and absorption. However, the selection of suitable in vitro methods should be based on a thorough understanding not only of human GI physiology but also of the drug and formulation properties. This review focuses on in vitro methods that can be applied to evaluate the effect of food intake on drug release from extended release (ER) products during preclinical formulation development. With the aid of different examples, it will be demonstrated that the combined and targeted use of various biorelevant in vitro methods can be extremely useful for understanding drug release from ER products in the fed state and to be able to forecast formulation-associated risks such as dose dumping in early stages of formulation development.

The impact of food intake on the luminal environment and performance of oral drug products with a view to in vitro and in silico simulations: a PEARRL review

Objectives

Using the type of meal and dosing conditions suggested by regulatory agencies as a basis, this review has two specific objectives: first, to summarize our understanding on the impact of food intake on luminal environment and drug product performance and second, to summarize the usefulness and limitations of available in vitro and in silico methodologies for the evaluation of drug product performance after food intake.

Key findings

Characterization of the luminal environment and studies evaluating product performance in the lumen, under conditions suggested by regulatory agencies for simulating the fed state, are limited. Various in vitro methodologies have been proposed for evaluating drug product performance in the fed state, but systematic validation is lacking. Physiologically based pharmacokinetic (PBPK) modelling approaches require the use of in vitro biorelevant data and, to date, have been used primarily for investigating the mechanisms via which an already observed food effect is mediated.

Summary

Better understanding of the impact of changes induced by the meal administration conditions suggested by regulatory agencies on the luminal fate of the drug product is needed. Relevant information will be useful for optimizing the in vitro test methods and increasing the usefulness of PBPK modelling methodologies.

The impact of food components on the intrinsic dissolution rate of ketoconazole

To accurately predict the in vivo performance of drugs from an in vitro dissolution test, the dissolution conditions used are supposed to be similar to those present in the gastrointestinal milieu. Post-prandial gastric fluid contains partially digested food mixtures consisting of fat, protein and carbohydrate. Despite this, the compendia dissolution medium recommended to simulate the gastric fluid is still composed of a simple solution of hydrochloric acid and sodium chloride with or without the addition of pepsin. Therefore, in this investigation, biorelevant dissolution media were developed to evaluate the impact of food constituents; milk with different fat contents, egg albumin, gelatin, casein, gluten, carbohydrates and amino acids on the intrinsic dissolution behavior of ketoconazole. Most of the food additives that were evaluated enhanced the apparent solubility of the drug but to different extents. The greatest enhancement in dissolution was observed in media containing either neutral amino acids or media based on milk mixtures. The formation of complexes between the drug and the additives most likely accounted for the solubilizing effect and in milk-containing media, the effect was attributed to the whole complex structure of milk rather than simply its fat content. These results highlight the potential effect of the type of ingested meal on drug dissolution and subsequent bioavailability.

Prediction of the in vivo performance of enteric coated pellets in the fasted state under selected biorelevant dissolution conditions

The purpose of this research was to predict the in vivo dissolution of lansoprazole from enteric coated pellets in the fasted state using a biorelevant flow-through dissolution method with low flow rates and volumes close to those in vivo. Additionally, a novel rotating stirring element, composed from magnet inserted in a silicone tube, was used to produce the movement of the pellets and expose them to slightly increased physical stress. Obtained dissolution results were compared to the dissolution results of our previous work using the USP IV with higher flow rate (11 ml/min). As drug release from enteric coated pellets usually starts in the small intestine, the influence of pellets' residence time in the gastric medium and additionally the effect of different media on drug release was studied. Prolongation of residence time in an acidic medium had only minor effect on the release rate after initial lag time, but significantly reduced the total amount of the drug released from both tested formulations, which was attributed to the drug's degradation in an acidic medium. The increased physical load on the pellets induced by the rotating stirring element compensated for the decrease of flow rate from 11 ml/min using the USP IV to 3 ml/min using the non-compendial system. Considering also gastric emptying kinetics good prediction of the in vivo release was achieved compared to in vivo absorption data obtained from a pharmacokinetic study under fasting conditions. Thus, using more physiologically relevant dissolution conditions, expressed through low volume and lower flow rate, and in combination with increased mechanical stress we obtained equally good in vitro/in vivo correlation as using USP IV and higher flow rates. Comparison of the dissolution results obtained with two different systems provided additional insight into product behaviour and improved prediction of in vivo performance.

Release characteristics of quetiapine fumarate extended release tablets under biorelevant stress test conditions

The aim of the present work was the investigation of robustness and reliability of drug release from 50 to 400 mg quetiapine extended release HPMC matrix tablets towards mechanical stresses of biorelevant intensity. The tests were performed under standard conditions (USP apparatus II) as well as under simulated gastrointestinal stress conditions. Mechanical stresses including pressure and agitation were applied by using the biorelevant dissolution stress test apparatus as it has been introduced recently. Test algorithms already established in previous studies were applied to simulate fasting gastrointestinal conditions. The dissolution experiments demonstrated striking differences in the product performance among standard and stress test conditions as well as dose strengths. In USP apparatus II, dissolution profiles were affected mainly by media pH. The dissolution experiments performed in biorelevant dissolution stress test device demonstrated that stress events of biorelevant intensity provoked accelerated drug release from the tablets.

Fed and fasted state gastro-intestinal in vitro lipolysis: In vitro in vivo relations of a conventional tablet, a SNEDDS and a solidified SNEDDS

The present study aims at evaluating the ability of a gastro-intestinal in vitro lipolysis model to predict the performance of two lipid formulations and a conventional tablet containing a poorly soluble drug, cinnarizine, in dogs, both in the fasted and fed state. A self-nano-emulsifying drug delivery system (SNEDDS) was either dosed in a hard gelatin capsule (SNEDDS-C) or loaded onto a porous tablet core (SNEDDS-T) and compared to a marketed conventional tablet (Conv) in an in vitro lipolysis model. The model simulates the digestion in the stomach and intestine during either the fasted or the fed state. Whole fat milk (3.5%) was used in the fed state model to mimic the dynamic lipolysis events after ingestion of food. The results were compared to a dog study published in this issue. In the fasted state in vitro lipolysis model, the amount of solubilized cinnarizine decreased in the order SNEDDS-C>SNEDDS-T>Conv, which correlated well with the in vivo bioavailability. In the fed state in vitro lipolysis model, cinnarizine was solubilized to the same degree for all formulations. Compared to the fasted state model, only the performance of the conventional tablet was improved, indicating food effect. This correlated with the in vivo study, where the tablet was the only formulation with a significant food effect. The fasted state model correlated well with the in vivo results and although the fed state model did not accurately predict the fed state in vivo results, it could predict which formulation that would exhibit a food effect.

The role of oral controlled release matrix tablets in drug delivery systems

Formulations that are able to control the release of drug have become an integral part of the pharmaceutical industry. In particular oral drug delivery has been the focus of pharmaceutical research for many years. This type of drug delivery has been at the centre of research due to its many benefits over conventional dosage. The focus of this review is on matrix tablets due to their widely use and simplicity of the formulation. This includes the discussion of various types of matrix tablets and factors affecting the drug release from these formulations. The mechanism of drug release from HPMC matrices is also discussed.

Biorelevant in-vitro performance testing of orally administered dosage forms

Objectives

This review focuses on the evolution and current status of biorelevant media and hydrodynamics, and discusses the usefulness of biorelevant performance testing in the evaluation of specific dosage form related lumenal processes.

Key findings

During the last 15 years our knowledge of the gastrointestinal environment (including the lower gut) has improved dramatically and biorelevant media composition and, to a lesser extent, biorelevant hydrodynamics, have been refined. Biorelevant dissolution/release testing is useful for the evaluation of formulation and food effects on plasma levels after administration of immediate release dosage forms containing low solubility compounds and after administration of extended release products. Lumenal disintegration times of immediate release dosage forms and the bile acid sequestering activity of resins in the lumen can also be successfully forecasted with biorelevant in vitro testing.

Summary

Biorelevant in-vitro performance testing is an important tool for evaluating intralumenal dosage form performance. Since the formulation of new active pharmaceutical ingredients for oral delivery is more challenging than ever before, efforts to improve the predictability of biorelevant tests are expected to continue.

From drug delivery systems to drug release, dissolution, IVIVC, BCS, BDDCS, bioequivalence and biowaivers

This is a summary report of the conference on drug absorption and bioequivalence issues held in Titania Hotel in Athens (Greece) from the 28(th) to the 30(th) of May 2009. The conference included presentations which were mainly divided into three sections. The first section focused on modern drug delivery systems such as polymer nanotechnology, cell immobilization techniques to deliver drugs into the brain, nanosized liposomes used in drug eluting stents, encapsulation of drug implants in biocompatible polymers, and application of differential scanning calorimetry as a tool to study liposomal stability. The importance of drug release and dissolution were also discussed by placing special emphasis on camptothecins and oral prolonged release formulations. The complexity of the luminal environment and the value of dissolution in lyophilized products were also highlighted. The second session of the conference included presentations on the Biopharmaceutics Classification Scheme (BCS), the Biopharmaceutics Drug Disposition Classification System (BDDCS), and the role of transporters in the classification of drugs. The current status of biowaivers and a modern view on non-linear in vitro-in vivo (IVIVC) correlations were also addressed. Finally, this section ended with a special topic on biorelevant dissolution media and methods. The third day of the conference was dedicated to bioequivalence. Emphasis was placed on high within-subject variability and its impact on study design. Two unresolved issues of bioequivalence were also discussed: the use of generic antiepileptic drugs and the role of metabolites in bioequivalence assessment. Finally, the conference closed with a presentation of the current regulatory status of WHO and EMEA.

Mechanistic study of the azithromycin dosage-form-dependent food effect

PURPOSE

Azithromycin capsules are known to exhibit a negative food effect, manifest as a decrease in azithromycin bioavailability in the fed state. Azithromycin tablets are known to be bioequivalent to capsules in the fasted state, but do not exhibit a food effect. In the present study, the involvement of gastric degradation of azithromycin to des-cladinose azithromycin (DCA) has been investigated as a possible mechanism for the observed capsule food effect.

METHODS

Healthy volunteers were dosed with azithromycin tablets and capsules, fasted and fed, in a four-way randomized crossover study. Serum levels of DCA were measured as a function of time post-dose. Natural log-transformed PK parameters were statistically analyzed using an ANOVA model appropriate for the study design.

RESULTS

When capsules were dosed to fed subjects, the systemic AUC for DCA was 243% of the value observed after fasted-state dosing, and the DCA C(max) was 270% of the value observed after fasted-state dosing. When azithromycin tablets were dosed in the fasted and fed states, there was no significant difference in systemic DCA.

CONCLUSION

Gastric degradation of azithromycin to DCA is the likely mechanism for the observed negative food effect observed for azithromycin capsules. This effect is not observed for tablets. These observations suggest that azithromycin capsules exhibit slow and/or delayed disintegration in the fed stomach, resulting in extended gastric residence and degradation of a portion of the gastrically retained azithromycin.