Modeling weight variability in a pan coating process using Monte Carlo simulations

Abstract

The primary objective of the current study was to investigate process variables affecting weight gain mass coating variability (CV m ) in pan coating devices using novel videoimaging techniques and Monte Carlo simulations. Experimental information such as the tablet location, circulation time distribution, velocity distribution, projected surface area, and spray dynamics was the main input to the simulations. The data on the dynamics of tablet movement were obtained using novel video-imaging methods. The effects of pan speed, pan loading, tablet size, coating time, spray flux distribution, and spray area and shape were investigated. CV m was found to be inversely proportional to the square root of coating time. The spray shape was not found to affect the CV m of the process significantly, but an increase in the spray area led to lower CV m s. Coating experiments were conducted to verify the predictions from the Monte Carlo simulations, and the trends predicted from the model were in good agreement. It was observed that the Monte Carlo simulations underpredicted CV m s in comparison to the experiments. The model developed can provide a basis for adjustments in process parameters required during scale-up operations and can be useful in predicting the process changes that are needed to achieve the same CV m when a variable is altered.

Improvement of Tablet Coating Uniformity Using a Quality by Design Approach

“…9a) that, in general, for higher speed, lower values of the SD/WG were observed, indicating that tablet-to-tablet variability decreased with increasing speed. This is in agreement with previously published studies (4,6). However, the effect of pan speed was small compared with other effects (i.e., the effect of weight gain) within the chosen range of speed.…”

“…It has been shown in previous studies that the tablet-totablet coating variability is inversely proportional to the square root of weight gain (28) or coating time (3,6,30). In this study, the evolution of the RSD as a function of square root of weight gain for all lots is displayed in Fig.…”

Influence of Process Parameters on Tablet Bed Microenvironmental Factors During Pan Coating

“…An overlap of spray regions would result in regions with much wetter conditions than desired, and tablets passing through those regions would receive additional spray, which could then lead to coating defects. Film roughness has been shown to be strongly affected by the balance between droplet spreading and drying, with a rougher film produced at a higher atomization air pressure (28). Excessive atomization air pressure can result in the production of smaller droplets that dry completely before reaching the tablet surface, leading to spray drying, loss of efficiency, and, in some cases, logo infilling or "orange peeling" coating defects.…”

Modeling of Pan Coating Processes: Prediction of Tablet Content Uniformity and Determination of Critical Process Parameters

“…The seed particle (tracer) was simulated by a random walk in the x and y directions with a step size in the x-direction based on the rotation speed of the rotor and a step size in the y-direction fitted to experimental results. Similarly Pandey et al 9 used a Monte Carlo approach to simulate the weight variability in a pan coating process. Typically they needed both the spray zone shape and the tablet movement information as model inputs.…”