Take Control of Your Formulations – An essential guide for selecting METHOCEL™ hydroxypropyl methylcellulose excipients

SYNOPSIS

Controlled release (CR) formulations are revolutionizing drug delivery across the pharmaceutical landscape. Offering advantages like enhanced therapeutic outcomes and patient convenience, this innovative drug formulation is experiencing rapid global growth. The popularity of CR formulations is particularly notable in epilepsy, diabetes, hypertension and chronic pain management, where safe, longterm treatment is needed.

However, as the market progresses to address the ever evolving and unique needs of patients, CR formulations are becoming more complex. To keep pace, the next generation of cutting-edge CR delivery systems demand even more from functional excipients.

Polymeric excipient solutions, like METHOCEL™ hydroxypropyl methylcellulose (HPMC), serve as a foundation for CR performance – essential for facilitating the gradual release of active ingredients over an extended period of time. Without them, CR mechanisms wouldn’t be possible. But do you know exactly how excipient properties impact CR performance?

Understanding this is pivotal for achieving tailored release profiles with differentiated performance – and staying one step ahead in the CR landscape with advanced formulations.

Ready to take control of your formulation?

Learn why excipient choice matters – using METHOCEL™ HPMC as an example – and unlock four considerations for mastering robust CR delivery performance.

WHY METHOCEL™ HPMC CHOICE MATTERS

Patients prefer solid oral dosage forms. And hydrophilic matrix systems are among the most widely used means for controlled drug delivery in solid oral dosage.

Functional excipients are essential in CR formulations as they help to control the release of the active ingredient over a specified time period; supporting therapeutic efficacy and patient compliance. Many innovative CR formulations, including hydrophilic matrix tablets, utilize high molecular weight, watersoluble cellulose ethers, like HPMC, to achieve desired CR performance. However, with an array of HPMC solutions (and other excipients) available – all with different molecular weights, degrees of substitution and viscosity – formulators face the challenge of selecting the most suitable HPMC type or grade to meet their specific release performance targets.

The first step in choosing the right excipient requires comprehensive knowledge of how the molecule’s specific properties influence drug release. To support formulators in leveraging the best excipient for their unique CR needs, we have outlined four things every CR drug manufacturer should know about HPMC chemistry.

1. Cellulose ether chemistry

The CR mechanism of a hydrophilic matrix tablet is achieved through the formation of a robust and continuous hydrogel layer around the matrix tablet. It forms when the tablet contacts an aqueous media – like fluid in the gastrointestinal tract – and HPMC particles near the tablet surface hydrate, swell, and coalesce; creating a swollen gel layer around the matrix core.

This gel later acts as a barrier, controlling the release of active ingredients from the dosage form and thereby regulating its release rate. At first glance, the excipient’s gel strength may appear essential for achieving the hydrogel layer. However, there are other factors at play. Don’t forget powder dissolution temperature (PDT)

Take methylcellulose (MC) and HPMC excipients as an example. Both produce clear and viscous solutions when dissolved at low temperatures, but MC forms a strong gel and HPMC forms a weak gel upon heating (Figure 1). , If gel strength is strongly linked to the development of the swollen hydrogel layer, this suggests that MC would outperform HPMC in CR applications. However, it does not.

HPMC excipients emerge as superior for CR functionality – despite forming weaker gels. The reason for this is because powder dissolution temperature (PDT) is a key factor to consider (Figure 2). Excipients are present as dry particles (and not as dissolved solutions) in CR matrix tablets, and they must first hydrate from dry state, swell and combine with other particles nearby to form the hydrogel layer. This suggests that the temperature at which the polymeric powder dissolves is a more important parameter for CR performance.

Key takeaway for formulators?

Polymer chemistry – whether it is MC or HPMC – impacts temperature-dependent hydration of the excipient particles (or PDT) in a matrix tablet. HPMC excipients – especially K-Chemistry grades – exhibit the highest PDTs (above body temperature), meaning they can more readily hydrate at physiological temperature to form a hydrogel layer around the matrix tablet.

2. Particle size

Another key factor for attaining a strong and uniform hydrogel layer – and facilitating reliable CR performance – is achieving a percolating network of HPMC particles throughout the matrix tablet. This is a continuous lattice of equally distributed HPMC particles, close enough to hydrate and coalesce and form the hydrogel layer.

The size of HPMC particles affects how well this network forms throughout the tablet. For example, smaller HPMC particles (45-125 µm) form a robust, contiguous hydrogel layer with low porosity upon hydration – reducing API release rates. However, larger HPMC particles (125–355 µm) form less contiguous swollen hydrogels with greater pore sizes, leading to faster API release rates.

Key takeaway for formulators?

The particle size of HPMC affects the ability of the excipient to form a percolating network of particles throughout the matrix tablet. If HPMC particles are larger, a higher concentration of HPMC will be needed to achieve this connected grid and slower release profiles.

See the full brochure on “Take Control of Your Formulations” here

(click the picture to download the brochure)

Source: IFF, brochure “Take Control of Your Formulations”, pharma.iff.com

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