Modulated release metoprolol succinate formulation based on ionic interactions: In vivo proof of concept

Development of Extended-Release Mini-Tablets Containing Metoprolol Supported by Design of Experiments and Physiologically Based Biopharmaceutics Modeling

The development of extended-release dosage forms with adequate drug release is a challenge for pharmaceutical companies, mainly when the drug presents high solubility, as in Biopharmaceutics Classification System (BCS) class I. This study aimed to develop extended-release mini-tablets containing metoprolol succinate (MS), while integrating design of experiments (DOE) and physiologically based biopharmaceutics modeling (PBBM), to predict its absorption and to run virtual bioequivalence (VBE) studies in both fasted and fed states. Core mini-tablet formulations (F1, F2, and F3) were prepared by direct compression and coated using nine coating formulations planned using DOE, while varying the percentages of the controlled-release and the pore-forming polymers. The coated mini-tablets were submitted to a dissolution test; additional formulations were prepared that were optimized by simulating the dissolution profiles, and the best one was submitted to VBE studies using GastroPlus® software. An optimized formulation (FO) containing a mixture of immediate and extended-release mini-tablets showed to be bioequivalent to the reference drug product containing MS when running VBE studies in both fasted and fed states. The integration of DOE and PBBM showed to be an interesting approach in the development of extended-release mini-tablet formulation containing MS, and can be used to rationalize the development of dosage forms.

Polymer Distribution and Mechanism Conversion in Multiple Media of Phase-Separated Controlled-Release Film-Coating

Phase-separated films of water-insoluble ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be utilized to tailor drug release from coated pellets. In the present study, the effects of HPC levels and the pH, type, ionic strength and osmolarity of the media on the release profiles of soluble metoprolol succinates from the EC/HPC-coated pellets were investigated, and the differences in drug-release kinetics in multiple media were further elucidated through the HPC leaching and swelling kinetics of the pellets, morphology (SEM) and water uptake of the free films and the interaction between the coating polymers and the media compositions. Interestingly, the drug release rate from the pellets in different media was not in agreement with the drug solubility which have a positive correlation with the drug dissolution rate based on Noyes–Whitney equation law. In particular, the drug release rate in acetate buffer at pH 4.5 was faster than that in other media despite the solubility of drug was relatively lower, regardless of the HPC levels. It may be attributed to the mutual effect between the EC and acetate buffer, which improved the permeability of the film. In contrast, the release of drug in HCl solution was dependent on the HPC levels. Increasing the levels of HPC increased the effects of hydrogen ions on the polymer of HPC, which resulted in a lower viscosity and strength of the gel, forming the larger size of pores in polymer films, thus increasing the drug diffused from the coating film. Further findings in phosphate buffer showed a reduction in the drug release compared to that in other media, which was only sensitive to the osmolarity rather than the HPC level and pH of the buffer. Additionally, a mathematical theory was used to better explain and understand the experimentally measured different drug release patterns. In summary, the study revealed that the effects of the media overcompensated that of the drug solubility to some extent for controlled-release of the coating polymers, and the drug release mechanism in multiple media depend on EC and HPC rather than on HPC alone, which may have a potential to facilitate the optimization of ideally film-coated formulations.

Pharmacokinetic Variability of Drugs Used for Prophylactic Treatment of Migraine

In this review, we evaluate the variability in the pharmacokinetics of 11 drugs with established prophylactic effects in migraine to facilitate 'personalized medicine' with these drugs. PubMed was searched for 'single-dose' and 'steady-state' pharmacokinetic studies of these 11 drugs. The maximum plasma concentration was reported in 248 single-dose and 115 steady-state pharmacokinetic studies, and the area under the plasma concentration-time curve was reported in 299 single-dose studies and 112 steady-state pharmacokinetic studies. For each study, the coefficient of variation was calculated for maximum plasma concentration and area under the plasma concentration-time curve, and we divided the drug variability into two categories; high variability, coefficient of variation >40%, or low or moderate variability, coefficient of variation <40%. Based on the area under the plasma concentration-time curve in steady-state studies, the following drugs have high pharmacokinetic variability: propranolol in 92% (33/36), metoprolol in 85% (33/39), and amitriptyline in 60% (3/5) of studies. The following drugs have low or moderate variability: atenolol in 100% (2/2), valproate in 100% (15/15), topiramate in 88% (7/8), and naproxen and candesartan in 100% (2/2) of studies. For drugs with low or moderate pharmacokinetic variability, treatment can start without initial titration of doses, whereas titration is used to possibly enhance tolerability of topiramate and amitriptyline. The very high pharmacokinetic variability of metoprolol and propranolol can result in very high plasma concentrations in a small minority of patients, and those drugs should therefore be titrated up from a low initial dose, depending mainly on the occurrence of adverse events.

Model drug as pore former for controlled release of water-soluble metoprolol succinate from ethylcellulose-coated pellets without lag phase: opportunities and challenges

The objective of the present study was to evaluate the feasibility of using model drug metoprolol succinate (MS) as a pore former to modify the initial lag phase (i.e., a slow or non-release phase in the first 1-2 h) associated with the drug release from coated pellets. MS-layered cores with high drug-layering efficiency (97% w/w) were first prepared by spraying a highly concentrated drug aqueous solution (60% w/w, 70°C) on non-pareils without using other binders. The presence of MS in ethylcellulose (EC) coating solution significantly improved the coating process by reducing pellets sticking, which often occurs during organic coating. There may be a maximum physical compatibility of MS with EC, and the physical state of the drug in the functional coating layer of EC/MS (80:20) was simultaneously crystalline and non-crystalline (amorphous or solid molecule solution). The lag phase associated with hydroxypropylcellulose (HPC) as a pore former was not observed when MS was used as a pore former. The drug release from EC/MS-coated pellets was pH independent, inversely proportional to the coating levels, and directly related to the pore former levels. The functional coating layer with MS as a pore former was not completely stabilized without curing. Curing at 60°C for 1 day could substantially improve the stability of EC/MS-coated pellets. The physical state of the drug in the free film of EC/MS (85:15) changed partially from amorphous to crystal when cured at 60°C for 1 day, which should be attributed to the incompatibility of the drug with EC.

Computer-based evolutionary search for a nonlinear conversion function for establishing in vitro-in vivo correlation (IVIVC) of oral drug formulations

Establishment of in vitro-in vivo correlation (IVIVC) accelerates optimization of desirable drug formulations and/or modification of the manufacturing processes in the scale-up and post-approval periods. This article presents a method of finding the optimal conversion function for establishing Level A point-to-point IVIVC, based on a computer-based evolutionary search technique. Gene expression programming (GEP) is a technique for optimizing a mathematical expression tree with the help of a genetic algorithm. A parameter optimization routine, which minimizes the number of parameters in the mathematical expression trees and estimates the best-fit parameter values, was implemented in the GEP algorithm. Feasibility of the computer program was investigated using the in vitro and in vivo data for sustained release diltiazem formulations. It provided a mathematical equation that, from their in vitro dissolution profiles, successfully predicts the plasma concentration profiles of three different formulations of diltiazem following oral administration. Because the present approach does not use intravenous injection data like conventional IVIVC analyses, it is widely applicable to the evaluation of various oral formulations.

Design and optimization of colon-targeted system of theophylline for chronotherapy of nocturnal asthma

The objective of the present work was to develop a delayed-onset controlled-release colon-targeted system of theophylline, and to achieve the chronotherapy of nocturnal asthma. The formulation consisted of a core tablet containing hydroxypropyl methylcellulose used for achieving controlled release of drug, and a Eudragit S100:ethyl cellulose (EC) coating capable of delaying the drug release. The system was optimized using a 3(2) full factorial design, wherein two factors [ratio of Eudragit S100:EC and the coating level (% w/w)] were evaluated for lag time, t(50) and t(80) . The optimum formulation consisted of Eudragit S100:EC in a 60:40 ratio and a coating level of 7.5% (w/w). Results showed that the tablets prepared according to the optimized values released no drug in the upper part of gastrointestinal tract; drug release was initiated at pH 6.4 (colon) after a lag time of 5 h. In vivo evaluation (pharmacokinetic studies and roentgenography) in rabbits revealed that the tablet remained intact until it reaches the colon and the drug release was initiated after a lag time of 5 h. Thus, it can be concluded that the developed system exhibited a promising colonic targeting and hence may be used for chronotherapy of nocturnal asthma.

Development and optimization of metoprolol succinate gastroretentive drug delivery system

Metoprolol succinate (MS) gastroretentive (GR) controlled release system was formulated to increase gastric residence time leading to improved drug bioavailability. Box-Behnken model was followed using novel combinations of sodium alginate (SA), sodium carboxymethylcellulose (NaCMC), magnesium alumino metasilicate (MAS) as independent variables. Floating lag time (Flag), t25, t50, t75, diffusion exponent as dependent variables revealed that the amount of SA, NaCMC and MAS have a significant effect (p < 0.05) on t25, t50, t75 and Flag. MSGR tablets were prepared and evaluated for mass, thickness, hardness, friability, drug content and floating property. Tablets were studied for dissolution for 24 h and exhibited controlled release of MS with floating for 16 h. The release profile of the optimized batch MS01 fitted first-order kinetics (R2 = 0.9868, n = 0.543), indicating non-Fickian diffusion or anomalous transport by diffusion and swelling.

Novel/conceptual floating pulsatile system using high internal phase emulsion based porous material intended for chronotherapy

The aim of the present study was to design a novel/conceptual delivery system using ibuprofen, anticipated for chronotherapy in arthritis with porous material to overcome the formulation limits (multiple steps, polymers, excipients) and to optimize drug loading for a desired release profile suitable for in vitro investigations. The objective of this delivery system lies in the availability of maximum drug amount for absorption in the wee hours as recommended. Drug loading using 3(2) factorial design on porous carrier, synthesized by high internal phase emulsion technique using styrene and divinylbenzene, was done via solvent evaporation using methanol and dichloromethane. The system was evaluated in vitro for drug loading, encapsulation efficiency, and surface characterization by scanning electron, atomic force microscopy, and customized drug release study. This study examined critical parameters such as solvent volume, drug amount, and solvent polarity on investigations related to drug adsorption and release mostly favoring low-polarity solvent dichloromethane. Overall release in all batches ranged 0.98-52% in acidic medium and 71-94% in basic medium. These results exhibit uniqueness in achieving the least drug release of 0.98%, an ideal one, without using any release modifiers, making it distinct from other approaches/technologies for time and controlled release and for chronotherapy.

Modulation and optimization of drug release from uncoated low density porous carrier based delivery system

The purpose of this research work was to explore an application of uncoated porous drug carrier prepared by single-step drug adsorption for a delivery system based on integration of floating and pulsatile principles intended for chronotherapy. This objective was achieved by utilizing 3(2) factorial design, solvent volume (X(1)) and drug amount (X(2)) as selected variables, for drug adsorption using solvents, methanol, and dichloromethane (DCM), of varying polarity. Nitrogen adsorption (N(2)), scanning electron microscopy of cross-sections, and atomic force microscopy were done to study adsorption patterns and their effect on release pattern. Drug release study was customized by performing for 6 h in acidic environment to mimic gastroretention followed by basic environment akin to transit phase. Correlation between porous data from mercury and N(2) adsorption was probably studied for the first time. Observed regression analysis values for pore volume, surface area, and drug release indicated the influence of selected variables. Total release range in acidic medium was 12.77-24.57% for methanol, 8.79-15.26% for DCM, and final release of 69.45-92.23% for methanol, and 60.16-99.99% for DCM influenced by varying internal geometries was observed. Present form of drug delivery system devoid of any additives/excipients influencing drug release shows distinct behavior from other approaches/technologies in chronotherapy by (a) observing desired low drug release (8%) in acidic medium, (b) overcoming the limitations of process variables caused by multiple formulation steps and different characteristic polymers, (c) reducing time consumption due to single step process, and (d) extending as controlled/extended release.

Ion pair-mediated transport of metoprolol across a three lipid-component PAMPA system

Parallel Artificial Membrane Permeability Assay (PAMPA) is a method to screen drug candidates for membrane permeability. The objective was to characterize the transport of a model weak base, metoprolol, across a three lipid-component PAMPA system (denoted A-PAMPA, for anionic-PAMPA) and challenge ion pairing as a mechanism for metoprolol transport. A-PAMPA was designed to mimic the lipid composition of the enterocyte's plasma membrane and included 1,2-dioleoyl-sn-glycero-3-[phospho-l-serine] (PS18:1) as an anionic lipid-component. Metoprolol flux was measured across A-PAMPA, as well as across three other PAMPA systems. Permeability studies were conducted under various conditions, with varying pH, ionic strength, and presence/absence of competing cations. Permeabilities of mannitol and benzoic acid, as model neutral and anionic solutes, were also measured. PAMPA membrane fluidity was inferred from anisotropy measurements in liposomes. Ion pairing between metoprolol and PS18:1 was assessed via NMR. Metoprolol transport across A-PAMPA was dominated by an ion pair-mediated mechanism (i.e. metoprolol-PS18:1 complex), rather than a membrane fluidity-mediated mechanism. Compared to other PAMPA systems, metoprolol permeability across A-PAMPA and PS18:1 was high. Permeability and anisotropy values suggested PS18:1 selectively facilitated metoprolol transport, while neutral lipid did not. Additional studies supporting ion pairing of metoprolol across A-PAMPA showed that a) metoprolol transport was self-inhibited across A-PAMPA but not across neutral lipid PAMPA; b) competing cations reduced metoprolol permeability across A-PAMPA but not across neutral lipid PAMPA; and c) NMR spectrum of a mixture of metoprolol and PS18:1 showed a broadening of some metoprolol peaks, presumably due to metoprolol interaction with anionic lipid. Metoprolol transport across a three lipid-component PAMPA system that contained anionic lipid was facilitated by apparent ion pairing.