Polymers are widely used in pharmaceutical products and it is difficult to develop a modern dosage form without any use of polymers. The main applications of polymer in pharmaceuticals include – as release controlling, binding, coating, suspending, emulsifying, and flocculating agents.
Hydroxypropyl methylcellulose (HPMC) or is a most commonly used polymer refers to soluble methylcellulose ethers. Hypromellose is used as a binder, hydrophilic matrix former, thickening agent and film former. HPMC a popular matrix forming material in oral controlled delivery systems are available in various viscosity grades ranging from 4000–100,000 mPas.
Most widely used types of HPMC in modified-release formulations are the Hypromellose 2208 (also known as K chemistry or grade) and Hypromellose 2910 (also known as E chemistry or grade). Where the first two digits (22/29) refer to the approximate percentage content of the more methoxy group (OCH3), and the second two digits (08/10) refer to the approximate percentage content of the more hydroxypropoxy group (OCH2CH(OH)CH3).
Such variations in the ratios of methoxy and hydroxypropoxyl substitutions and molecular weight affect their properties such as organic solubility, thermal gelation temperature in aqueous solution, swelling, diffusion, and drug-release rate. Where methoxy group indicates hydrophobicity and hydroxypropoxy group indicates hydrophilicity.
Hypromellose 2208 (K type)
- Methoxy group: 20-24
- Hydroxypropoxy group: 7 -12
Hypromellose 2910 (E type)
- Methoxy group: 28-30
- Hydroxypropoxy group: 7 -12
Based on the methoxy and hydroxypropoxy group ratio of HPMC K-type and E-type, K-type HPMC show better water solubility. That’s why for higher dissolution in initial time point most of the XR/CR formula used K-type HPMC.
HPMC matrix show sustained release pattern by two mechanisms
- Swelling & diffusion: Suitable for high soluble drug
- Erosion & dissolution: Suitable for low soluble drug
A list of common polymer and their application in pharmaceutical products
Hypromellose: Bioadhesive material; coating agent; controlled-release agent; dispersing agent; dissolution enhancer; emulsifying agent; emulsion stabilizer; extended-release agent; film-forming agent; foaming agent; granulation aid; modified-release agent; mucoadhesive; release-modifying agent; solubilizing agent; stabilizing agent; suspending agent; sustained-release agent; tablet binder; thickening agent; viscosity-increasing agent.
Hydroxypropyl Cellulose: Coating agent; emulsifying agent; stabilizing agent; suspending agent; tablet binder; thickening agent; viscosity-increasing agent.
Methylcellulose: Coating agent; emulsifying agent; suspending agent; tablet and capsule disintegrant; tablet binder; viscosity-increasing agent.
Few Polymer Brand Used in Pharmaceutical Products
- Methocel
- Ethocel
- Eudragit
- Kollicoat
- Benecel
Different Polymers and Their Uses
- Cellulose Acetate (semipermeable) - Prolonged release tablet
- Cellulose Acetate Phthalate (soluble in >pH 6) - Delayed release tablet
- Ethylcellulose (Insoluble) - Prolonged release tablet
- Hydroxypropyl cellulose (Soluble) - Immediate release tablet)
- Hypromellose (Soluble) - Immediate release tablet)
- Polyvinyl Alcohol (Soluble) - Immediate release tablet)
- Shellac (Soluble in >pH 7) - (Delayed release and Prolonged release tablet)
