Polymer microparticles for drug delivery

DETAILED DESCRIPTION OF THE INVENTION The term microparticle is used herein to include nanoparticles.
The microparticles preferably have a size in the range 10 nm to 200.
mu.
m.
The water-soluble polymer is preferably soluble in both water and dichloromethane (DCM).
The term "biodegradable polymer" is used herein to include polymeric systems which can degrade into low molecular weight compounds which are known to be involved normally in metabolic pathways.
The term also includes polymer systems which can be attached in the biological milieu so that the integrity of the system, and in some cases of the macromolecules themselves, is affected and gives fragments or other degradation by-products which can move away from their site of action, but not necessarily from the body.
The ratio of biodegradable polymer to water-soluble polymer is in the range 99.
9:1.
0 to 10:90, more preferably 90:10 to 10:90.
Suitable biodegradable polymers for producing the microparticles are polyesters such as polylactide, polyglycolide, copolymers of lactide and glycolide, polyhydroxybutyrate, polycaprolactone, copolymers of lactic acid and lactone, copolymers of lactic acid and PEG, copolymers of a-hydroxy acids and .
alpha.
-amino acids (polydepsipeptides), polyanhydrides, polyorthoesters, polyphosphazenes, copolymers of hydroxybutyrate and hydroxyvalerate, poly(ethylene carbonate), copoly(ethylene carbonate).
polyethylene terephthalate or mixtures of these polymers.
The preferred resorbable/biodegradable polymers are lactide homopolymers poly(L-lactide), poly(D,L-lactide), and copolymers of lactide and glycolide such as 50:50 poly(DL lactide co-glycolide)(PLG).
The PLG preferably has a molecular weight in the range 5-100 kD.
While poly(ethylene glycol) (PEG) is the preferred water soluble polymer for mixing with the biodegradable polymer, other suitable water soluble polymers include poly(oxyethylene oxide)(PEO), poly(oxyethylene)-poly(oxypropylene) ?PEO-PPO! block copolymers such as tri-block PEO-PPO-PEO copolymers (POLOXAMERS