· Hypromellose 1828

· Hypromellose 2208

· Hypromellose 2906

· Hypromellose 2910

The first two digits refer to the approximate percentage content of the methoxy group while the last two digits refer to the approximate percentage content of the hydroxypropoxy group, calculated on a dried basis.

In some textbooks, hypromellose types are classified on the basis of the degrees of methoxy and/or hydroxyproyl substitution into three main groups, which correspond to the USP codes as shown below:

· Hypromellose Type C: High Methoxy and High Hydroxypropyl content

· Hypromellose Type D: High Methoxy and Low Hydroxypropyl content

· Hypromellose Type E: Medium Methoxy and Medium Hydroxypropyl content

Type	Letter Code	Methoxy Content %	Hydroxypropyl Content %
1828	C	16.5-20.0	23.0-32.0
2208	D	19.0-24.0	4.0-12.0
2906	D	27.0-30.0	4.0-7.5
2910	E	28.0-30.0	7.0-12.0

It is not uncommon for some manufacturers to use their own codes for different grades of hypromellose. For example, Dupont (formely, Dow Chemical) uses codes E, F, and K, which principally indicate the degree of substitution.

· Hypromellose K grades correspond to Hypromellose 2208

· Hypromellose F grades correspond to Hypromellose 2906

· Hypromellose E grades correspond to Hypromellose 2910

In addition, the letter codes above may be accompanied by a number that indicates the viscosity of a 2% aqueous solution, usually multiplied by 100 as C or 1000 as M.

Some grades have additional acronyms that provide further information on the application of that particular grade. For instance, P stands for premium, LV for low viscosity, CR for controlled release, G for granular, or FG for food grade.

In the pharmaceutical sector, Hypromellose 2208, 2906 and 2910 are the grades most commonly used as binders, film coatings and matrix formulation. Hypromellose 1828 is also available, although not widely used in the development of dosage forms.