USP-NF packaging system suitability : a simple yet powerful tool for differentiating packaging performances in terms of water permeability

Introduction
Controlling water vapour transmission is essential for maintaining the stability of moisture-sensitive drugs, since moisture can degrade active pharmaceutical ingredients (APIs) and affect dosage performance. To determine the more effective protective option, we compared the water vapour permeability of two packaging materials using the standardized USP <671> method, which provides reliable and specific transmission rates to distinguish between the performance of different types of packaging.

Objective
To compare the performance of two models of multidose bottles intended for solid oral forms, in terms of water vapor permeability, according to the protocol defined by USP <671>.

Materials and Methods
In this study, the two packaging models tested were.
Bottle A : body made of high-density polyethylene (HDPE) with a snap-on cap made of low-density polyethylene (LDPE) (Laboratoires des Gélules et des Azymes, La Seyne-sur-Mer, France).
Bottle B : body made of polyethylene terephthalate (PET) with a snap-on cap made of LDPE (Laboratoires des Gélules et des Azymes, La Seyne-sur-Mer, France).
The protocol used complies with chapter USP <671> of the United States Pharmacopeia and aims to compare the performance of these two multi-dose bottle models intended for solid oral dosage forms, in terms of water vapor permeability. For this, 12 bottles of each model were filled to one-third of their volume with silica gel, hermetically sealed, then placed in a climatic chamber maintained at 40 ± 2 °C and 75 ± 5 % relative humidity (RH) for 35 days. The weight of the bottles was measured on days 7, 14, 21, 28, and 35 (± 1h). For each bottle, a curve representing the change in weight (in grams) over time was plotted, and the slope (expressed in g/day/bottle) was calculated by linear regression. The average slopes and their standard deviations were then determined for each group.

Results
Bottle A exhibited an average permeability rate of 3.525 ± 0.61367 mg/day/bottle, whereas Bottle B showed a notably higher rate : 17.85 ± 0.235488 mg/day/bottle. These results clearly demonstrate a difference in barrier performance between the two types of bottle tested. Furthermore, the obtained curves demonstrate linear mass gain progression and good intra-series reproducibility.

Discussion
The results clearly show that the HDPE/LDPE bottle (Bottle A) is more effective at preventing water vapour transmission than the PET/LDPE bottle (Bottle B), with a permeability rate approximately five times lower. This significant difference is consistent with the intrinsic properties of the materials used : HDPE is renowned for its exceptional moisture barrier properties, whereas PET, despite its good mechanical properties and transparency, tends to exhibit higher water vapour permeability.

Keywords : Drug Packaging, Drug Storage, Drug Compounding.