IVIVC of controlled release formulations: Physiological–dynamical reasons for their failure

IVIVC Revised

PURPOSE

To revise the IVIVC considering the physiologically sound Finite Absorption Time (F.A.T.) and Finite Dissolution Time (F.D.T.) concepts.

METHODS

The estimates τ and τd for F.A.T. and F.D.T., respectively are constrained by the inequality τd ≤ τ; their relative magnitude is dependent on drug's BCS classification. A modified Levy plot, which includes the time estimates for τ and τd was developed. IVIVC were also considered in the light of τ and τd estimates. The modified Levy plot of theophylline, a class I drug, coupled with the rapid (30 min) and very rapid (15 min) dissolution time limits showed that drug dissolution/absorption of Class I drugs takes place in less than an hour. We reanalyzed a carbamazepine (Tegretol) bioequivalence study using PBFTPK models to reveal its complex absorption kinetics with two or three stages.

RESULTS

The modified Levy plot unveiled the short time span (~ 2 h) of the in vitro dissolution data in comparison with the duration of in vivo dissolution/absorption processes (~ 17 h). Similar results were observed with the modified IVIVC plots. Analysis of another set of carbamazepine data, using PBFTPK models, confirmed a three stages absorption process. Analysis of steady-state (Tegretol) data from a paediatric study using PBFTPK models, revealed a single input stage of duration 3.3 h. The corresponding modified Levy and IVIVC plots were found to be nonlinear.

CONCLUSIONS

The consideration of Levy plots and IVIVC in the light of the F.A.T. and F.D.T. concepts allows a better physiological insight of the in vitro and in vivo drug dissolution/absorption processes.

Revamping Biopharmaceutics-Pharmacokinetics with Scientific and Regulatory Implications for Oral Drug Absorption

PURPOSE

The Wagner-Nelson and Loo-Riegelman methods developed in the 1960s and used since for the construction of percent of drug absorbed as a function of time as well as in in vitro in vivo correlations are re-considered in the light of the physiologically sound Finite Absorption Time (F.A.T.) concept developed recently.

METHODS

The classical equations for the percentage of drug absorption as a function of time were modified by taking into account the termination of drug absorption at F.A.T., replacing the parameters associated with the assumption of infinite drug absorption.

RESULTS

Mathematical analysis using the relevant Physiologically Based Pharmacokinetic Finite Time (PBFTK) models assuming one- or two-compartment drug disposition, revealed that the modified %absorbed versus time curves are of bilinear type with an ascending limb intersecting the horizontal line at F.A.T. A computer-based methodology is described for the estimation of F.A.T. from experimental data. More than one linear ascending limb is found when more than one absorption phase is operating. Experimental data were analyzed and the estimates for F.A.T were found to be similar to those derived from nonlinear regression analysis using PBFTPK models.

CONCLUSION

These results place an end to the routinely reported exponential %absorbed versus time curves prevailing in biopharmaceutics-pharmacokinetics since their inception in the'60 s. These findings point to the use of the F.A.T. concept in drug absorption research and regulatory guidelines such as deconvolution techniques for the assessment of drug input rate, stochastic mean absorption time calculations, population analyses, in vitro in vivo correlations and bioequivalence guidelines.

In vitro-in vivo correlation of inhalable budesonide-loaded large porous particles for sustained treatment regimen of asthma

Large porous particles (LPPs) are well-known vehicles for drug delivery to the lungs. However, it remains uncertain whether or to which extent the in vitro drug release behavior of LPPs can be predictive of their in vivo performance (e.g., systemic exposure and therapeutic efficacy). With regard to this, three budesonide-loaded LPP formulations with identical composition but distinct in vitro drug release profiles were studied in vivo for their pharmacokinetic and pharmacodynamic behavior after delivery to rat lung, and finally, an in vitro/in vivo correlation (IVIVC) was established. All formulations reduced approximately 75% of the uptake by RAW264.7 macrophages compared with budesonide/lactose physical mixture and showed a drug release-dependent retention behavior in the lungs of rats. Likewise, the highest budesonide plasma concentration was measured for the formulation revealing the fastest in vitro drug release. After deconvolution of the plasma concentration/time profiles, the calculated in vivo drug release data were successfully utilized for a point-to-point IVIVC with the in vitro release profiles and the predictability of the developed IVIVC was acceptable. Finally, effective therapy was observed in an allergic asthma rat model for the sustained drug release formulations. Overall, the obtained in vitro results correlate well with the systemic drug exposure and the therapeutic performance of the investigated lung-delivered formulations, which can provide an experimental basis for IVIVC development in the pulmonary-controlled delivery system. STATEMENT OF SIGNIFICANCE: Large porous particles (LPPs) are well-known vehicles for drug delivery to the lungs. However, it remains uncertain whether or to which extent the in vitro drug release behavior of LPPs can be predicted by their in vivo performance (e.g., systemic exposure and therapeutic efficacy). With regard to this, three budesonide-loaded PLGA-based LPP formulations with identical composition but distinct in vitro drug release profiles were studied in vivo for their pharmacokinetic and pharmacodynamic behavior, and finally, an in vitro/in vivo correlation (IVIVC) was established. It was demonstrated that the influence of the in vitro drug release profile was obvious during lung retention, systemic exposure, and therapeutic efficacy measurements. An IVIVC (Level A) was successfully established for the budesonide-loaded LPPs delivered to the airspace of rats for the first time. Taken together, the present work will clearly support research and development activities in the field of controlled drug delivery to the lungs.

Determining the polymer threshold amount for achieving robust drug release from HPMC and HPC matrix tablets containing a high-dose BCS class I model drug: in vitro and in vivo studies

It is challenging to achieve mechanically robust drug-release profiles from hydrophilic matrices containing a high dose of a drug with good solubility. However, a mechanically robust drug release over prolonged period of time can be achieved, especially if the viscosity and amount of the polymer is sufficiently high, above the "threshold values." The goal of this research was to determine the hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose (HPMC) polymer threshold amount that would enable robust drug release from matrix tablets containing a high dose of levetiracetam as a class I model drug according to the Biopharmaceutical Classification System (BCS). For this purpose, formulations containing HPC or HPMC of similar viscosity range, but in different amounts, were prepared. Based on the dissolution results, two final formulations were selected for additional in vitro and in vivo evaluation to confirm the robustness and to show bioequivalence. Tablets were exposed to various stress conditions in vitro with the use of different mechanically stress-inducing dissolution methods. The in vitro results were compared with in vivo results obtained from fasted and fed bioequivalence studies. Under both conditions, the formulations were bioequivalent and food had a negligible influence on the pharmacokinetic parameters C max and area under the curve (AUC). It was concluded that the drug release from both selected formulations is mechanically robust and that HPC and HPMC polymers with intrinsic viscosities above 9 dL/g and in quantities above 30% enable good mechanical resistance, which ensures bioequivalence. In addition, HPC matrices were found to be more mechanically robust compared to HPMC.

In-vitro/in-vivo characterization of trans-resveratrol-loaded nanoparticulate drug delivery system for oral administration

OBJECTIVES

The current studies entail successful formulation of systematically optimized (OPT) nanoparticulate drug delivery system to increase the oral bioavailability using Eudragit RL 100 of trans-resveratrol (t-RVT), and evaluate their in-vitro/in-vivo performance.

METHODS

t-RVT-loaded Eudragit RL 100 nanoparticles (t-RVT NPs) were prepared by nanoprecipitation method. The nanoparticles (NPs) were systematically optimized using 3(2) central composite design and the OPT formulation located using overlay plot. The pharmacokinetic and in-vivo biodistribution of t-RVT NPs were investigated in rats, and various levels of in-vitro/in-vivo correlation (IVIVC) were established.

KEY FINDINGS

The OPT formulation (mean particle size: 180 nm) indicated marked improvement in drug release profile vis-à-vis pure drug and marketed formulation (MKT). Augmentation in the values of Ka (5.64-fold) and AUC0-24 (7.25-fold) indicated significant enhancement in the rate and extent of bioavailability by the optimized trans-resveratrol-loaded Eudragit RL 100 nanoparticles (OPT-t-RVT NPs) compared with pure drug. Level A of IVIVC was successfully established. OPT-t-RVT NPs showed 4.11-fold rose in the values of t-RVT concentrations in liver. In-situ single pass intestinal perfusion studies construed remarkable enhancement in the absorptivity and permeability parameters of OPT-t-RVT NPs.

CONCLUSIONS

The results, therefore, insight into the role of solubility enhancement and trounce enterohepatic recirculation for improving the oral bioavailability of t-RVT.

Controlled release of ropinirole hydrochloride from a multiple barrier layer tablet dosage form: effect of polymer type on pharmacokinetics and IVIVC

The purpose of the present study was to control in vitro burst effect of the highly water-soluble drug, ropinirole hydrochloride to reduce in vivo dose dumping and to establish in vitro-in vivo correlation. The pharmacokinetics of two entirely different tablet formulation technologies is also explored in this study. For pharmacokinetics study, FDA recommends at least 10% difference in drug release for formulations to be studied but here a different approach was adopted. The formulations F8A and F9A having similar dissolution profiles among themselves and with Requip® XL™ (f 2 value 72, 77, 71 respectively) were evaluated. The C max of formulation F8A comprising hypromellose 100,000 cP was 1005.16 pg/ml as compared to 973.70 pg/ml of formulation F9A comprising hypromellose 4000 cP irrespective of T max of 5 and 5.75 h, respectively. The difference in release and extent of absorption in vivo was due to synergistic effect of complex RH release mechanism; however, AUC0-t and AUC0-∞ values were comparable. The level A correlation using the Wagner-Nelson method supported the findings where R (2) was 0.7597 and 0.9675 respectively for formulation F8A and F9A. Thus, in vivo studies are required for proving the therapeutic equivalency of different formulation technologies even though f 2 ≥ 50. The technology was demonstrated effectively at industrial manufacturing scale of 200,000 tablets.

Keeping a critical eye on the science and the regulation of oral drug absorption: a review

This review starts with an introduction on the theoretical aspects of biopharmaceutics and developments in this field from mid-1950s to late 1970s. It critically addresses issues related to fundamental processes in oral drug absorption such as the complex interplay between drugs and the gastrointestinal system. Special emphasis is placed on drug dissolution and permeability phenomena as well as on the mathematical modeling of oral drug absorption. The review ends with regulatory aspects of oral drug absorption focusing on bioequivalence studies and the US Food and Drug Administration and European Medicines Agency guidelines dealing with Biopharmaceutics Classification System and Biopharmaceutic Drug Disposition Classification System.

A novel beads-based dissolution method for the in vitro evaluation of extended release HPMC matrix tablets and the correlation with the in vivo data

The aim of this work was to establish alternative in vitro dissolution method with good discrimination and in vivo predictability for the evaluation of HPMC extended release matrix tablets. For this purpose, two different HPMC matrix tablet formulations were first evaluated by a range of conventional dissolution testing methods using apparatus 1, apparatus 2, and apparatus 3 according to US Pharmacopoeia. Obtained results showed low discrimination between the tested samples. Afterward, a novel dissolution testing method which combines plastic beads and apparatus 3 was developed with the aim to better mimic the mechanical forces that occur in vivo. Results showed that sufficiently large mechanical stress with high dips per minute program setting (apparatus 3) was needed to obtain in vitro discriminative results, which are in accordance with the in vivo data. The in vivo relevance of the method was confirmed with the establishment of the level A in vitro-in vivo correlation.

Elucidating the role of dose in the biopharmaceutics classification of drugs: the concepts of critical dose, effective in vivo solubility, and dose-dependent BCS

PURPOSE

To develop a dose dependent version of BCS and identify a critical dose after which the amount absorbed is independent from the dose.

METHODS

We utilized a mathematical model of drug absorption in order to produce simulations of the fraction of dose absorbed (F) and the amount absorbed as function of the dose for the various classes of BCS and the marginal cases in between classes.

RESULTS

Simulations based on the mathematical model of F versus dose produced patterns of a constant F throughout a wide range of doses for drugs of Classes I, II and III, justifying biowaiver claim. For Classes I and III the pattern of a constant F stops at a critical dose Dose(cr) after which the amount of drug absorbed, is independent from the dose. For doses higher than Dose(cr), Class I drugs become Class II and Class III drugs become Class IV. Dose(cr) was used to define an in vivo effective solubility as S(eff) = Dose(cr)/250 ml. Literature data were used to support our simulation results.

CONCLUSIONS

A new biopharmaceutic classification of drugs is proposed, based on F, separating drugs into three regions, taking into account the dose, and Dose(cr), while the regions for claiming biowaiver are clearly defined.

Selection of the most suitable dissolution method for an extended release formulation based on IVIVC level A obtained on cynomolgus monkey

OBJECTIVE

The purpose of this study is primarily to identify the most suitable in vitro dissolution method(s) for their ability to predict the in vivo performance of extended release prototype tablet formulations designed for a new chemical entity, Biopharmaceutic Classification System class II drug, weak base, based on the data collected in cynomolgus monkey.

MATERIALS AND METHODS

Different types of buffer at different pH were selected as dissolution medium resulting in a broad variety of release patterns (slow to fast). The in vivo and in vitro data were put in relation.

RESULTS

As a consequence of the discrimination between both tested formulations, the in vitro-in vivo correlation (IVIVC) qualities and shapes changed significantly. The obtained level A showed that the simple HCl medium was superior to biorelevant media and media containing surfactant when investigating IVIVCs in cynomolgus monkey. In addition, the results of dissolution in HCl suggested rather a diffusion mechanism of the extended release matrix formulation as the main factor of the release.

CONCLUSION

Adjusting dissolution testing conditions to match the behavior of the formulations in vitro with that in vivo by taking into account the properties of the drug and the formulation is a straightforward and useful approach in identifying a predictive method in the development of the IVIVC. These investigations will definitely help by derisking of new formulations as well as by rating changes in existing formulations with regard to their impact on bioavailability before entry into human.