Hydroxypropyl methylcellulose – what a tongue-twister! In this case, the acronym HPMC is so much easier to pronounce. But what does it mean when we say that we use HPMC capsules for our products?

HPMC is also known as E464. It originated as an excipient in pharmaceutical products, most often in the form of fine powder for tablet production. It consists of modified cellulose from a sustainable vegetable source, e.g., cotton, pine or poplar.

Since the end of the 00’es, HPMC has also been used for capsule production. HPMC is a water-soluble substance which dissolves in the digestive tract to allow the dietary supplement content of the capsule to be absorbed by the intestines. If HPMC capsules end up in nature, they will decompose and release primarily carbon (C) and water (H₂O). The disintegration time of a capsule in the digestive tract is between 30 and 75 minutes.

In contrast to gelatine capsules, HPMC capsules do not contain amino acids that may produce chemical reactions when exposed to the contents of the capsule.

Plastic - do you know the actual meaning of the term?

HPMC is referred to as an artificial substance; however, this is not quite true. It is a semi-synthetic material produced on the basis of natural substances. It is also not quite true when HPMC is categorised as microplastic.

Let’s clarify this: To most people, plastic is a substance produced from mineral oil, e.g., plastic bags. In materials chemistry, the term plastic is used for describing materials that are made from synthetic or natural substances and which is mouldable.

Consequently, it is not wrong to say that HPMC is a plastic but it may confuse people. HPMC is a water-soluble, bio-compatible and bio-degradable material – and thus is misleading to talk about HPMC as microplastic in terms of environment impact.

References

• Al-Tabakha, Moawia M. (2010): HPMC capsules: current status and future prospects. In Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Societe canadienne des sciences pharmaceutiques 13 (3), pp. 428-442. DOI: 10.18433/J3K881
• Deshmukh, K.; et al. (Eds.) (2017): Biopolymer Composites in Electronics. Biopolymer Composites With High Dielectric Performance: Interface Engineering: Elsevier.
• Majee, Sutapa Biswas; Avlani, Dhruti; Biswas, Gopa Roy (2017): HPMC AS CAPSULE SHELL MATERIAL: PHYSICOCHEMICAL, PHARMACEUTICAL AND BIOPHARMACEUTICAL PROPERTIES. In Int J Pharm Pharm Sci 9 (10), p. 1. DOI: 10.22159/ijpps.2017v9i10.20707.
• Williams, R. O.; Sykora, M. A.; Mahaguna, V. (2001): Method to recover a lipophilic drug from hydroxypropyl methylcellulose matrix tablets. In AAPS PharmSciTech 2 (2), E8. DOI: 10.1208/pt020208