What is it: HPMC is a chemically modified cellulose polymer that is off-white in color and considered safe for human consumption. It is most commonly used as an alternative to gelatin and gluten in vegan-friendly products
Hydroxypropyl Methylcellulose (HPMC) is multifunctional as a lubricant, foam enhancer and stabilizer, thickener, emulsion stabilizer and film former for hair and skin care products. HPMC is especially useful in surfactant systems for its foam enhancing properties, helping with the formation of bubble structure, leading to richer, longer lasting lather. HPMC has a high tolerance for both salt and alcohol.
Techniques for Dispersion
- The preferred method is to begin by heating approximately 1/3 of the total formulation water to 167°F (75°C) or higher. Add the HPMC to the vortex of agitated and heated water. Mix until fully dispersed. HMPC will not dissolve at this temperature. After complete dispersion, add the remaining water at room temperature or colder and continue mixing for 30 minutes after the total solution has cooled to 77°F. (25°C) or less. Proceed with the formulation.
- If heating is impossible, it is preferred to slurry the HPMC in a non-solvating media, such as glycerin or PEG, then add the slurry to the vortex of vigorously agitated water. Adding HPMC directly to cold water is not preferred, but if necessary, must be done very slowly under vigorous agitation. Expect longer mixing times for complete dissolution.
- Alternative to Gelatin: It serves as an alternative to gelatin because of its vegetarian source and its physical similarities to gelatin. This is extremely useful if you need to make your own supplements since it can help vegetarians and those with dietary restrictions consume supplements and medications.
- Alternative to Gluten: It is also a very good replacement for gluten in gluten-free food. In baking bread, it limits “both the diffusion and the loss of water from the bread crumb and the interactions between starch and protein macromolecules,” which results in softer gluten-free bread and reduces staleness during storage.
Other uses: It acts as a thickening agent, coating polymer, binder, and bioadhesive in pharmaceutical, food, and industrial manufacturing.
Is it safe?: In an FDA study with rats, there were no significant toxic effects other than growth retardation once HPMC reached levels of 20 to 30% of the rats’ diet. This study noted that growth retardation may be contributed to malnutrition and not the amount of HPMC. In another study, rabbits were injected with 2% HPMC for over a month and there were no observations of toxicity or irritation. Overall, the FDA sees it as a non-toxic and non-irritating inactive ingredient that is safe for human use and consumption.
Common HPMC sources:
- Supplement capsules
- Drug carrier
- Coating agent
- Emulsifier in ointments
- Tabletting agent
- Eye drops
- Bakery goods
- Ice cream
- Salad dressing
- Sauce mix
- Building materials
- Printing and dyeing of textiles
- HPMC: A versatile hydrophilic polymer
Thursday, November 02, 2006 08:00 IST
Subal C BasakThe advancement of drug delivery is, and will always be dependent on polymers as both drug encapsulants and vehicles of drug carriage: either protecting a drug during its passage through body (or in storage by preventing moisture entry) until its release, or controlling its release. An appropriate selection of the polymer matrix is necessary in order to develop a successful drug delivery system. In fact the focus on developing novel techniques using polymer, to deliver drugs more efficiently has resulted in a more cost-effectively new pharmaceuticals as well as extending the life of existing patent franchise. Hydroxypropyl methylcellulose is the dominant vehicle used for the preparation of oral controlled drug delivery systems. HPMC is the abbreviation for hydroxypropyl methylcellulose, which has the official name of hypromellose in the USP and the European Pharmacopoeia. One of the HPMC’s most significant characteristics is the high swellability, which has a noteworthy effect on the release behavior of an incorporated drug.Physicochemical properties: HPMC is a cellulose ether, prepared from alkali treated cellulose that is reacted with methyl chloride and propylene oxide. The substitution group, -OCH2CH(CH3)OH, forms on each anhydroglucose unit of the polymeric cellulose chain, contains a secondary hydroxyl on the number two carbon and may also be considered to form a propylene glycol ether of cellulose. HPMC possesses varying ratios of hydroxypropyl and methyl substitution, a factor which influences organic solubility and the thermal gelation temperature of aqueous solutions. Thus HPMC is a propylene glycol ether of methylcellulose; its structural formula is depicted in Fig. 1. Patents disclosing the process of making HPMC were granted to Dow Chemical in 1960 (US 2949252). The physicochemical properties are affected by: the methoxy group content; the hydroxypropoxy group content; and the molecular weight. The USP distinguishes four different types of HPMC, classified according to their relative methoxy and hydroxypropoxy content: HPMC 1828, HPMC 2208, HPMC 2906 and HPMC 2910. The USP describes a method to determine viscosity of an aqueous 2% solution of the polymer using suitable viscometer.The viscosity ranges from 3 to100000 mPas. The apparent viscosity serves as a measure for the average chain length of the polymer. Examples of HPMC polymers of low viscosity grade include those available under the brand names Methocel E5, Methocel E15 LV, Methocel F 50 LV and Methocel K 100 LV whose viscosities at 2% are 5, 15, 50 and 100 mPas, respectively. Examples of HPMC polymers having medium viscosity include those available under the brand names Methocel E4M and Methocel K4M both of whose viscosity is 4000 mPas. High viscosity HPMC includes K15M and K100M whose viscosities are 15000 and 100000 mPas, respectively. The molecular weight ranges from 13000 to 208000.Pharmaceutical uses of HPMC: HPMC has been used in food and pharmaceutical industries in the USA and European countries for many years. It has many pharmaceutical uses, as a drug carrier, a coating agent, a tabletting agent, an emulsifier in ointments, a thickener in suspensions, a non-ionic surfactant, a binder, and a film forming agent. HPMC has properties know as reversible thermal gelation that is the basis of many above mentioned applications – it forms gels when heated but return to solubility when cooled. HPMC forms hydrophilic matrices which mainly act by diffusion in controlling the release of a drug from the matrices. When exposed to an aqueous medium, such matrix does not disintegrate, but immediately after hydration develops a highly viscous gelatinous surface barrier which controls the drug release from and the liquid penetration into the centre of the matrix system.HPMC capsules: Two-piece capsules have been used for almost a century in the pharmaceutical field, and gelatin has been adopted as the main material of these capsules due to its excellent characteristic as a gelatinizer. Several materials have been examined as a substitute for the gelatin in two-piece hard capsules. HPMC has become a successful alternative material for two-piece capsules and is actually on the market in the world. HPMC capsules have been developed for both pharmaceutical products and dietary supplements. QUALI-V, developed by Shionogi Qualicaps, is the first HPMC capsule developed for eventual use in pharmaceutical products. HPMC capsules will be of interest for those who, for religious, cultural or other reasons wish to avoid capsules made from animal derived component.HPMC as medicine: It belongs to the group of medicines known as artificial tears. It is used to relieve dryness and irritation caused by reduced tear flow.Other uses: Food uses include as emulsifier, thickening agent, stabilizer, gellant, film former, protective colloid, fat barrier, suspending agent in food products; including bakery goods, ice creams, salad dressings, and sauce mixes etc. The gels produced from HPMC have desirable fat like functional properties. HPMC used in food use does not have impact on nutritional quality of the food, as the methylcelluoses are not digestible and make no caloric contribution to the diet. In baked products, it improves tenderness and extends shelf life. It is used in personal care products as a thickening agent and foam stabilizer. HPMC can also be used in chemical industries as film-forming agent in petrochemical, building materials, agrochemical, ink, printing and dyeing of textile, paper making etc.
- (The author isreader in PharmacyAnnamalai University, Tamil Nadu)