Hydroxypropyl Methylcellulose|HPMC

Hydroxypropyl Methylcellulose is a derivative of cellulose and is a semisynthetic excipient used in oral liquid, ophthalmic, nasal, topical, and oral solid dosage form preparations. It is a tasteless, odorless granular, or fibrous powder. Hydroxypropyl Methylcellulose is commonly known as 

• HPMC
• Hypromellose
• Methocel
  

Numbering System

• USP 32 defines the substitution by numbering systems for HPMC or Hypromellose.
• A 4-digit numbering system is used.
• The first two digits show the %age of the methoxy group.
• The last 2 digits show the %age content of the hydroxypropoxy group.

Examples

• Hypromellose 2208
• Hypromellose 2906
• Hypromellose 2910

2208 is known as K grade and 2910 is known as E grade

Nomenclature

• For HPMC the initial alphabets K,E, F represent methoxyl hydroxypropyl substitutions in the polymer.
• After alphabet the  numeric value represents the viscosity of HPMC in millipascal second of that specific grade determined at 2% concentration in water at 20 °C.
• M represent 1000
• LV is Low Viscosity
• VLV is a Very Low Viscosity

Example

• HPMC K 100 M
• HPMC K 100 LV

Grades 

HPMC is available in different viscosity grades and molecular weight.

Different grades areas

• K100 M
• K100 LV
• E 15 LV
• E5
• VLV

Uses of  HPMC

HPMC  is used as

• Tablet & Capsule Binder
• Film-Forming Agent
• Thickening Agent 
• Viscosity Enhancer
• Thickening Agent
• Matrix forming Agent for
  • Sustained release
  • Modified Release
  • Extended-Release
• Wetting agent for contact lenses.
• In Nasal preparations. 0.1%

HPMC As Binder

2-5% w/w solution of HPMC is used as a tablet and capsule binder for wet granulation and dry granulation.

As Film Former

• 2-20% w/w HPMC solution is used in tablet coating to mask the unpleasant taste and it form the layer of polymer over the tablet.
• Low viscosity grades are used for aqueous solution coating.
• High viscosity grades are used for organic solvent coating.

As Matrix

• HPMC is used in tablet and capsules dosage form to modify the drug release profile.
• High viscosity grades of HPMC are used in 10-80% concentration for tablet and capsule formulations to form a matrix.
• The matrix is formed on contact with the water and it entraps the drug and alters its release according to requirements.

In Oral liquids

• HPMC is used to increase the viscosity of oral liquid formulations.
• It is also used s a thickening agent at concentration 0.25-5%.

In Topical Preparations

• HPMC is used to increase the viscosity of topical formulations.
• It acts as a thickening agent in topical preparations.

In Ophthalmic Preparations

• HPMC is used in ophthalmic preparations because it forms a more clear solution than methylcellulose
• it is used in artificial tears and to enhance the viscosity of eye drops and used concentration is 0.45-1%.
• HPMC in liquid preparations may promote microbial growth so antimicrobial agents should be added in ophthalmic preparations.

Solubility

It is soluble in cold water and insoluble in hot water.

Storage

HPMC absorbs moisture from the environment so it should be stored in a tightly closed container.