Development and characterization of multiparticulate system as an alternative to unit dosage forms containing drugs with diverse release profiles

Background

Currently, the Bilayer tablets, Tablet in tablet and Inlay tablets composed of Glimepiride (GMP) and Pioglitazone (PGH) as immediate release part, and Metformin (MFH) as sustained-release part are available for the treatment of type II diabetes mellitus (T2DM). In these products, there is a possibility of the incomplete release of immediate release part (GMP and PGH) due to their entrapment into high viscosity gel barrier of MFH sustained-release part when drug product comes in contact with media. Therefore, the present study was aimed to deliver the above combination drugs in the form of hard gelatin capsules (as unit dosage form) containing MFH sustained-release (MFH-SR) pellets and immediate release pellets of PGH and GMP (PG-IR).

Results

The MFH-SR and GP-IR pellets, prepared by extrusion and spheronization technique, were optimized based on the drug content and % cumulative drug release. The MFH-SR pellets formulation (batch A6) has shown maximum drug content, and sustained-release of MFH similar to marketed glucophage tablet while, the GP-IR pellets formulation (batch B5) has displayed maximum drug contents and immediate release of GMP and PGH; thus, these batches were considered for further characterizations. The optimized MFH-SR and GP-IR formulations have shown particle sizes of 0.23 ± 0.0010 mm and 0.35 ± 0.0018 mm, respectively. Besides, the formulations exhibited good micromeritics properties. The in vivo pharmacokinetic study in rabbits has demonstrated comparable bioavailability of the drugs from pellets and the marketed formulations following oral administration. Further, the pellets were found to be stable for 6 months at 40 ± 2 °C/75% ± 5%RH.

Conclusions

The study results revealed that the multiparticulate systems with varied release profiles could be a promising approach to overcome drug release issues associated with the unit dosage forms.

Relationship between amorphous solid dispersion in vivo absorption and in vitro dissolution: phase behavior during dissolution, speciation, and membrane mass transport

Enzalutamide is a fast crystallizing, hydrophobic compound that has solubility limited absorption in vivo. Given the low aqueous solubility of this compound, it was of interest to evaluate amorphous formulations in vitro and in vivo. Amorphous solid dispersions (ASD) of enzalutamide were prepared with the hydrophilic polymers, hydroxypropyl methylcellulose acetate succinate (HPMCAS) and copovidone (PVPVA). A side-by-side diffusion cell was developed as an in vitro characterization tool to discriminate enzalutamide ASDs based upon the solute thermodynamic activity achieved during dissolution and its impact on the subsequent membrane transport rates, phase behavior, and drug speciation. The same formulations were then tested in vivo in rats using oral dosing of ASD suspensions. Different levels of plasma exposure were observed between the ASDs, which could be correlated to the phase behaviors of the ASDs following dissolution. Unsurprisingly, ASDs that underwent crystallization show lower plasma exposures. However, differences were also observed between ASDs that dissolved to form nanosized amorphous drug aggregates versus those that dissolved to yield only supersaturated solutions, with the former outperforming the latter in terms of the plasma exposure. These observations highlight the importance of thoroughly understanding the phase behavior of an amorphous formulation following dissolution and the need to discriminate between different types of precipitation, specifically crystallization versus glass liquid phase separation to form nanosized amorphous aggregates.

An insight into cochleates, a potential drug delivery system

Cochleates are solid particulates made up of large continuous lipid bilayer sheets rolled up in a spiral structure with little or no internal aqueous phase. Cochleates improve the oral bioavailability and efficacy of the drugs by decreasing side effects.

In vitro and in vivo studies on HPMC-K-100 M matrices containing naproxen sodium

Controlled release (CR) matrix tablets of naproxen sodium were prepared by wet granulation using hydroxypropyl methyl cellulose (HPMC-K-100 CR) as the hydrophilic rate controlling polymer. The effect of the concentration of the polymer and different fillers on the in vitro drug release rate was studied. The studies indicated that the drug release can be modulated by varying the concentration of the polymer and the fillers. An optimized formulation subjected to accelerated stability studies for 3 months revealed that the developed CR tablets are stable. A complete cross-over bioavailability study of the optimized formulation of the developed CR tablets and marketed immediate release tablets was performed in 6 healthy male volunteers. The extent of absorption of drug from the CR tablets was significantly higher than that for the marketed naproxen sodium tablet due to lower elimination rate and longer half-life.

Design of controlled release delivery systems using a modified pharmacokinetic approach: a case study for drugs having a short elimination half-life and a narrow therapeutic index

The objectives of peroral controlled release drug delivery systems (CRDDS) are to maintain therapeutically effective plasma drug concentration levels for a longer duration thereby reducing the dosing frequency and to minimise the plasma drug concentration fluctuations at steady state by delivering drug in a controlled and a reproducible manner. Drug delivery rate, duration of delivery and the dosing interval are the target features for any temporal CRDDS. The classical pharmacokinetic model for designing CRDDS [Drug Dev. Ind. Pharm. 15 (1989) 1073] assumes the time of drug delivery (t(del)) to be less than the dosing interval. However, termination of drug release from such a CRDDS at t(del) and/or a declining drug input function towards the terminal phase of t(del) from a first order kinetic CRDDS can have severe implications on plasma drug concentration and steady state fluctuations for a drug with very short half-life. A case study is presented in this paper, wherein by means of theoretical calculations using a classical pharmacokinetic approach, it is shown that a first order kinetic CRDDS for hypothetical drugs with short elimination half-life and different pharmacokinetic conditions would result in sub-therapeutic plasma concentrations at least for some time during the dosing interval at steady state. In order to avoid sub-therapeutic plasma drug concentrations a modification in classical pharmacokinetic model is proposed and discussed through theoretical calculations for different hypothetical pharmacokinetic situations and a practical single dose pharmacokinetic study with a first order kinetic CRDDS for nifedipine (a short half-life drug; about 2h). It is shown that improved therapeutic efficacy could be expected from a CRDDS developed based on proposed modification in the classical pharmacokinetic model.

Pharmacodynamic aspects of sustained release preparations

The sustained release (SR) mode of drug administration has certain features that have an important impact on the magnitude of the pharmacologic response: (a) it minimizes fluctuation in blood drug concentrations (i.e. between peak and trough). However, due to the pronounced non-linear relationship between drug concentration and pharmacologic effect (i.e. pharmacodynamics) the impact of this property differs considerably as a function of the shape of the pharmacodynamic profile and the position of the specific range of concentrations on the curve of this profile; (b) it produces a slow input rate which tends to minimize the body's counteraction to the drug's intervening effect on regulated physiological processes; and (c) it provides a continuous mode of drug administration. This important pharmacodynamic characteristic may produce, in certain cases, an opposite clinical effect than that attained by an intermittent (pulsatile) mode of administration of the same drug. For many drugs with non-concentration-dependent pharmacodynamics, the exposure time, rather than the AUC, is the relevant parameter and it can therefore be optimized by SR preparations. The slow input function may minimize hysteresis in cases where the site of action is not in a rapid equilibrium with the blood circulation. The pharmacodynamics of the desired effect(s) and/or adverse effect(s) may also be influenced by the site of administration, especially in cases where the drug is delivered directly to its site of action. These factors demonstrate the important influence of the mode of administration on the pharmacological and clinical outcomes. In addition, they highlight the need to include these pharmacodynamic considerations in all stages from drug development to the optimization of their clinical use.

Percutaneous permeation of basic compounds through shed snake skin as a model membrane

Relationships between the in-vitro permeability of basic compounds through shed snake skin as a suitable model membrane for human stratum corneum and their physiochemical properties were investigated. Compounds with low pKa values were selected to compare the permeabilities of non-ionized forms of the compounds. Steady-state penetration was achieved immediately without a lag time for all compounds. Flux rate and permeability coefficient were calculated from the steady-state penetration data and relationships between these parameters and the physicochemical properties were investigated. The results showed that permeability may be controlled by the lipophilicity and the molecular size of the compounds. Equations were developed to predict the permeability from the molecular weights and the partition coefficients of basic compounds.

Relative bioavailability of oral sustained-release and regular-release oxprenolol tablets at steady-state

The relative bioavailability of a test sustained-release (SR) oxprenolol tablet against an approved regular-release (RR) tablet has been investigated at steady-state. In a randomized two-way crossover study, one tablet of 160 mg SR oxprenolol once every 24 h and one tablet of 80 mg RR oxprenolol once every 12 h were given to 12 healthy volunteers for 5 days. Blood samples were collected from each subject just prior to each dose-administration on days 1 through 4, and at scheduled time points on day 5 and analysed for oxprenolol concentration using HPLC. The SR tablet resulted in 42 per cent reduction in mean peak drug levels (p = 0.0341) and a statistically non-significant 14 per cent increase in mean trough levels (p = 0.8357) than the RR tablet. However it required 160 per cent longer time to reach average steady-state concentrations (Css) on day 5 (1.38 h for SR versus 0.53 h for RR; p = 0.0205). The mean area under the plasma drug concentration-time curve at steady state (AUC96-120) with the SR tablet was approximately 18 per cent lower than that observed with the RR tablet, and the degree of fluctuation (DF) was reduced by 30 per cent (2.81 for SR versus 4.11 for RR; p = 0.0069). On average, a single dose of SR tablet and two doses of RR tablets maintained the drug levels above a constant Css of 204.6 ng ml-1 for 7.88 and 7.65 h, respectively (p = 0.3513).