Development of a new controlled-release formulation of chlorpheniramine maleate using in vitro/in vivo correlations

Current Applications of Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) in Pharmaceutical Analysis: Review

The present review encompasses various applications of multivariate curve resolution- alternating least squares (MCR-ALS) as a promising data handling, which is issued by analytical techniques in pharmaceutics. It involves different sections starting from a concise theory of MCR-ALS and four detailed applications in drugs analysis. Dissolution, stability, polymorphism, and quantification are the main four detailed applications. The data generated by analytical techniques associated with MCR-ALS deals accurately with different challenges compared to other chemometric tools. For each reviewed purpose, it was explained how MCR-ALS was applied and detailed information was given. Different approaches were introduced to overcome challenges that limit the use of MCR-ALS efficiently in pharmaceutical mixture were also discussed.

A nomogram to evaluate intrinsic absorption rate constants of potential oral prolonged-release candidates

The purpose of this study was to devise a simple method to determine whether or not a drug's absorption rate constant favored the selection of that drug for an oral prolonged-release drug delivery system (DDS). Computer simulations were used to observe the drug time-course in the DDS, the gastrointestinal tract, and the cumulative amount absorbed following administration of an 8-, 12-, and 24-hr zero-order DDS. For each DDS, the drug's intrinsic absorption rate constant, ka, was systematically varied from 0.1 to 10 hr-1. Results demonstrated that the DDS controlled the absorption rate whenever drug release was rate-limiting. However, the release rate did not determine the length of time that a DDS controlled the absorption rate. Instead, the duration of DDS-controlled absorption increased as the ka value increased. When ka > or = 2 hr-1, the DDS controlled more than 80% of the 8-, 12-, and 24-hr dosing intervals. Conversely, when ka < or = 0.12 hr-1, the DDS failed to control absorption. In conclusion, this investigation developed a technique to ascertain the rate-limiting step when a zero-order DDS releases a drug that undergoes first-order absorption. This technique was employed to construct a nomogram that allows its users to estimate the duration of control by an 8-, 12-, or 24-hr DDS based on the ka value for the drug.

Evaluation and comparison of dissolution data derived from different modified release dosage forms: an alternative method

Dissolution testing is an essential requirement for the development, establishment of in vitro dissolution and in vivo performance (IVIVR), registration and quality control of solid oral dosage forms. The objective of the present study was to investigate the effect of delivery system positioning in accordance with the USP 23-recommended dissolution methods and the proposed modification on drug release from controlled release systems having different operating release mechanisms, namely, swellable floatable, swellable sticking and osmotic pump. The delivery systems were evaluated by placing each dosage form either in the dissolution vessel in accordance with the USP 23 methods or over/below a designed ring/mesh device for achieving full surface exposure to the dissolution medium for sticking or floatable systems respectively. Results indicate that the overall release profiles from the sticking and floatable systems of theophylline are sensitive to their positioning in the dissolution vessel (P<0.05). Furthermore, release of diltiazem hydrochloride from the sticking system also demonstrated sensitivity (P<0.05). In contrast, the floatable dosage form of this latter drug with the application of a helical wire sinker, or when it was placed below the ring/mesh assembly, or by allowing the dosage form to float, did not show sensitivity (P>0.05) for the overall release behavior. This was attributed to the greater solubility of diltiazem hydrochloride (50% solubility in water at 25 degreesC) in comparison to theophylline which is a sparingly soluble drug (0.85% solubility in water at 25 degreesC). Drug release from the osmotic pump appeared to be identical under the given experimental conditions (P>0.05). Statistical analysis of data was performed by comparing the t50%, t70%, t90%; mean dissolution times (MDT50%, MDT70%, MDT90%); the "difference factor, f1" and "similarity factor, f2". It is concluded that the results derived from the application of the "similarity factor, f2" are superior to the individual time points (e.g. tx%) and MDTx% values in differentiating between overall release patterns or the border line release profile differences. It also became apparent that in the case of the swellable sticking systems full surface exposure to the dissolution medium results in greater release rate. For the osmotic pump the required osmotic pressure threshold necessary for constant rate drug delivery appears to have reached independent of the hydrodynamic conditions. A successful and more accurate evaluation of dissolution data can be derived when full surface exposure is considered and this can be accomplished by dissolution method modification with the aid of the designed ring/mesh assembly.

Formulation and preparation of controlled release pellets of salbutamol by the air suspension technique

A controlled release preparation of salbutamol may improve patient compliance, minimise side effects and be valuable in the treatment of nocturnal asthma by extending drug action throughout the night. The aim of the study was therefore to formulate a controlled release pellet preparation of salbutamol via the air suspension technique. The study established that curing for 24 h at 38 +/- 0.5 degrees C was necessary for homogeneous film coats of Eudragit RS30D and hence stable drug release characteristics. Pellets coated with 6% Eudragit RS30D (polymer), 12.5% triethyl citrate (plasticiser) and 0.5% magnesium stearate (antitackiness agent) displayed desirable controlled drug release characteristics over the 8 h testing period. The manufacturing conditions employed in the study were shown to be reproducible thus ensuring reproducibility of drug release characteristics between batches of salbutamol controlled release pellets. Short term stability testing on the newly formulated pellets indicated no significant change in drug release characteristics relative to the initial drug release data when stored for 8 weeks at room temperature 20 +/- 2 degrees C or 37 degrees C with 80% Relative Humidity or at low temperature (5 +/- 1 degrees C). However, pellets stored at 40 degrees C showed a slower in-vitro drug release after 8 weeks of storage and therefore failed to maintain their initial drug release profile.

Design and evaluation of transdermal chlorpheniramine maleate drug delivery system

The study was to develop a transdermal therapeutic system for chlorpheniramine maleate (CPM). The diffusion characteristics of CPM were determined using Franz diffusion cells, from gelled ethanol-water solutions of CPM (5, 10, and 20%). TESTSKIN Living Skin Equivalent (LSE) was used to study the enhancement effect of ethanol-water solutions. The 0.6 volume fraction of ethanol gave the highest diffusion rate of CPM (Jss = 1.591 mg/cm2h). The diffusion and partition coefficient data revealed that changes in ethanol volume fraction of the vehicle and ethylene vinyl acetate (EVA) membrane characteristics directly affect CPM partitioning and diffusion across EVA membranes and EVA-pressure sensitive adhesive (PSA) laminates. The data also suggest a possible interaction of CPM with the PSA. The steady state fluxes attained with 20% CPM gel is 34 micrograms/cm2h, which is enough to keep the drug within its therapeutic plasma levels.

Correlation of in vitro release rate and in vivo absorption characteristics of four chlorpheniramine maleate extended-release formulations

An in vitro/in vivo correlation was established for four formulations of chlorpheniramine maleate (histamine, H1-blocker) extended-release tablets exhibiting different in vitro release rate characteristics. In vitro release rate data were obtained for 12 individual tablets of each formulation using the USP Apparatus 2, paddle stirrer at 50 rpm in 1000 ml of distilled water at 37.0 +/- 0.5 degrees C. Inspection of the individual and mean release rate data indicated that the in vitro release rate of chlorpheniramine maleate was consistent with the intended design of the four extended-release formulations. The in vivo bioavailability and pharmacokinetics of these formulations were evaluated in 24 healthy subjects under fasting conditions. Wagner Nelson analyses of the in vivo data revealed extended release absorption profiles for all four formulations. Linear regression analyses of the mean percentage of dose absorbed versus the mean in vitro release resulted in a statistically significant correlation (r2 greater than 0.98, P less than 0.001) for each formulation. Qualitative rank-order correlations were observed among all combinations of in vitro and in vivo parameters. These data support a Level A correlation between the in vitro release rate profiles and the in vivo absorption for chlorpheniramine maleate determined under fasting conditions.