Not Much Ado About Coatings

There are more than 100 different coatings used on tablets and capsules. While many have a biological effect—enteric coatings or controlled- release coatings that delay releasing the active(s)—others simply add visual appeal and, more importantly, brand recognition. 

The classic example is the “purple pill.” The product’s proper name is Nexium, and even if you’ve never taken it, you probably knew that thanks to brand messaging on TV and elsewhere. You probably also have personal experience—or what we now call a narrative—about which prescription and nonprescription medicines you take. It likely includes a visual mental model of those tablets and capsules. 

I call this a “visual landscape” of your daily routine, and it’s a strong engagement factor in determining how likely you are to take a tablet or capsule as prescribed. I’ve previously published research [1], as have others [2, 3], about the strong influence size, shape, and color can have on the public’s uptake of and adherence to medicine in tablet or capsule form. There is no sign that the effects of these physical factors will abate. In fact, manufacturers are getting more adventurous with tablet morphologies lately, and it is not uncommon to have branding play a role in determining a tablet’s configuration. 

In some cases, a company’s logo brings to mind the shape of the tablet, and sometimes the tablet resembles the brand’s logo. Both serve as powerful visual signals that you have the “real McCoy,” the original, branded, innovator drug product. When done well, the result is a perception of higher quality that justifies a higher price than the generic form. The innovator tablet may even have a more powerful placebo effect than its generic counterpart. The tablet’s form may also offer a modicum of counterfeiting protection. 

More of the Same? 

As for the next generation of coatings, the recent trends will likely continue: Visual branding coupled with dissolution-control characteristics and protection of the active ingredient(s). PK/PD studies haven’t resolved any systematic differences between the various non-enteric coatings in terms of drug product efficacy, so there’s every reason to continue pursuing different—and perhaps better—coatings. As the resolution of QC assays become continues to increase, differentiation of the effects of excipients are becoming evident [4]. It raises the question of how differential effects will look when studied in a clinical context. Are they relevant? If not, what level of difference makes them relevant? 

Utility Versus Marketability 

The pharmaceutical industry doesn’t spend much R&D money on coatings, so people can’t work from some agreed-upon set of optimized practices that balance the utility of a coating with its marketability. It’s more trial and error than anything, and unless there’s an adverse market event, safety concern, or consumer signal, manufacturers are unlikely to get much feedback from the market about the coatings they use. In short, people are subtly motivated by coatings, but they don’t care about them. 

Furthermore, I’m not sure we need to make people care about them. Conversely, if a coating were to look good and provide an unarguable benefit—resistance to photo-degradation and moisture cross-permeability while preventing bacteria from accumulating on the surface of tablets kept on countertops, in pockets, etc.—then it could be a gamechanger. In that case, we’d need to assess the unintended consequences before the coating was used on marketed products. For instance, would a bacteriostatic or bactericidal coating disrupt the patient’s gut microbiome? 

The truth is, no matter how much money is spent to develop coatings, the public will continue to swallow coated tablets and capsules by the billions every year. But please don’t let that stop you, formulators, from making improvements. After all, corded telephones worked just fine, so why would anyone need a smartphone? Wait. Excuse me. I need to reply to a colleague’s text. 

References 

1. Locwin, B. (2011). The effect of size, shape, and color on medication tolerability and acceptance. Tablets & Capsules (9)1, 24-28. 

2. Stegemann, S. et al. (2011). OTC products: Understanding consumer expectations and perceptions. Tablets & Capsules (9)1, 14-18. 

3. Bar-Shalom, D. et al. (2016). The quest for easier-to-swallow tablets. Tablets & Capsules 14(1), 35- 39. 

4. Afonso-Pereira, F. et al. (2016). Sex differences in excipient effects: Enhancement in ranitidine bioavailability in the presence of polyethylene glycol in male, but not female, rats. Int J Pharm 506(1), 237-244.