Parenteral Delivery of Peptides and Proteins - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 545

11.4 Polymers Used in Parenteral Delivery of P/P

Polymers used in the formulation of delivery systems for either P/P drugs or other
conventional drugs must be biocompatible and have reasonable mechanical strength.
Specific applications of the delivery systems may depict other desirable properties
such as whether the release of the drug should occur through permeation from a poly-
meric membrane or by degradation of the polymeric matrix [132] . These polymers can
be broadly classified as nondegradable and degradable or biodegradable polymers.

11.4.1 Nondegradable Polymers
Nondegradable polymers, due to their limitations over their biodegradable counterparts,
are generally now not in much use except for applications in implantable systems. This
category of polymers is very limited and includes hydrophilic polymers such as poly-
acrylamide or hydrophobic polymers such as ethylene vinyl acetate (EVAc) copoly-
mer and silicone elastomers [133,134] . These nonbiodegradable polymers are listed
in Table 11.1 . Silicone elastomers when fabricated into matrices have been shown
to release macromolecules for more than 100 days [133,134] . The release rates from

Table 11.1 Polymers Used in the Formulation of Drug Delivery Systems for P/P Drugs

Chemical Class Polymer

1. Nonbiodegradable polymers

Synthetic and semisynthetic polymers
Cellulose derivatives

Carboxymethyl cellulose, cellulose acetate, cellulose acetate
propionate, ethyl cellulose, hydroxypropyl methylcellulose

Silicones Colloidal silica, polydimethylsiloxane, polymethacrylates,

poly(methyl methacrylate), polyhydro(ethylmethacrylate)

Miscellaneous Ethyl vinyl acetate, polyvinyl pyrrolidone, poloxamers, poloxamines

2. �iodegradable polymers �iodegradable polymers

Synthetic polymers
Polyamides Poly(imino carbonates), polyamino acids

Polyanhydrides Poly(sebacic acid), poly(adipic acid), poly(terphthalic acid)

Polyesters Poly(lactic acid), poly(glycolic acid), poly(hydroxy butyrate),

poly(-caprolactone), poly(-malic acid), poly(dioxanones)

Phosphorous-based
polymers

Polyphosphates, polyphosphazenes, polyphosphonates

Miscellaneous Polyacetals, poly(cyano acrylates), polydihydropyrans, polyortho

esters, polyurethane

Natural polymers
Polysaccharides

Agarose, alginate, carrageenan, chitosan, cyclodextrins, dextran,
hyaluronic acid, pectin

Proteins Albumin, collagen, gelatin