Exploring Excipient Functionality - Pharmaceutical Technology

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PharmTech Europe

Exploring Excipient Functionality
This technical forum is part of a special issue on Solid Dosage and Excipients.

Pharmaceutical Technology
Volume 35, pp. s6-s11

Pharmaceutical sugars

Jennifer Trevor, PhD, senior business development manager, Ferro Pfanstiehl Laboratories

The International Pharmaceutical Excipients Council (IPEC) provides 13 broad categories of excipients for solid dosage forms based upon function: binders, disintegrants, fillers, lubricants, glidants, compression aids, colors, sweeteners, preservatives, suspending/dispering agents, film-formers/coatings, flavors, and printing inks. Key features of excipients used in solid dosage manufacturing have traditionally been based upon flowability and particle size, among other characteristics.

One factor to consider when choosing an excipient is the desired release characteristics, whether it be immediate, sustained, or modified release (1). Quick-dissolving tablets have garnered more attention of late, especially with regard to using trehalose, a disaccharide of glucose, in solid-dosage formulation (2). One important feature that make this an attractive excipient for this usage is that it does not absorb water readily in the crystalline state, which lends to enhanced stability and reduced stickiness (3). Ohtake et al. recently wrote an extensive review article on the unique usages of trehalose in solid dosage forms. The authors noted that the information on trehalose-containing pharmaceuticals in the US is limited; however, there are a number of patents claiming the use of trehalose in solid-dosage applications.

Another attractive attribute of trehalose is the avoidance of Schiff bases from the reaction of aldehydic sugars with primary and secondary amines, such as what occurs with lactose. Trehalose does not react with amino groups and therefore is an attractive choice as a bulking agent. Additionally, anhydrous trehalose is not subject to undue hardness, such as lactose, and dissolves readily. Thus, the potential for developing trehalose in solid-dosage formulations is expanding.

Pharmaceutical sugars section references

1. V. Joshi, Drug Delivery Technol. 2 (6), 1–4 (2002).

2. S. Ohtake and J. Wang, J. Pharm. Sci. , DOI: 10.1002/jps.22458, Feb. 18, 2011.

3. K. Takeuchi and N. Banno, Fragrance J. 7 (7), 39–47 (1998).

Film coatings in taste-masking and moisture protection

Phil Butler, technical sales manager, coatings of pharma ingredients and services at BASF

Coating of solid oral dosage forms is an effective and economical route to providing moisture protection and taste-masking properties to moisture sensitive and bitter- tasting active ingredients (1). To achieve both properties using the same polymer, chemical functionality needs to be designed to provide not only insolubility in saliva (pH 6.8–7.2) for protection from unpleasant taste, but also reduced affinity to water for moisture protection.

Figure 1: Solubility of methyl methacrylate and diethylaminoethyl methacrylate copolymer dispersion.
Methyl methacrylate and diethylaminoethyl methacrylate copolymer dispersion (Kollicoat Smartseal 30 D, BASF SE) provides this dual functionality along with a fast release of active ingredients in the stomach (see Figure 1). The diethylaminoethyl basic functional groups result in an insoluble polymer at basic and neutral pH values and a quick-dissolving polymer at pH values below 5.5 (2).

Figure 2: Quinine hydrochloride dissolution in ph 6.8 phosphate buffer.
The performance as a taste-masking agent was evaluated by a human-taste panel. This assessment correlates very well with results from in vitro dissolution tests at pH 6.8 (see Figure 2), which proved to be a reasonable substitute and therefore suitable for quality-control purposes. The results in Figure 3 demonstrate that coating levels of 4–5 mg/cm2 of a Kollicoat Smartseal 30 D based formulation can effectively mask the unpleasant taste of quinine hydrochloride tablets.


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