FORMULATION AND EVALUATION OF MICROSPHERES PRESENTED BY DADHICHI K THAKKAR M.PHARM SEMISTER -I Guided by :-Dr UPENDRA PATEL DEPARTMENT OF PHARMACUETICAL TECHNOLOGY ARIHANT COLLEGE OF PHARMACY GUJARAT TECHNICAL UNIVERSITY. .
The oral route is considered as the most promising route of drug delivery. Conventional drug delivery system achieves as well as maintains the drug concentration within the therapeutically effective range needed for treatment, only when taken several times a day.
This results in a significant fluctuation in drug levels. A well defined controlled drug delivery system can overcome some of the problems of conventional therapy and enhance the therapeutic efficacy of a given drug..
There are various approaches in delivering a therapeutic susbstance to the target site in sustained controlled release fashion using microspheres as carrier for drug
SINGLE EMULSION BASED METHOD Aq.Solution/suspension of polymer Dispersion in organic phase (Oil/Chloroform) Microspheres in organic phase Microspheres in organic phase MICROSPHERES Stirring, Sonication CROSS LINKING Chemical cross linking (Glutaraldehyde/Formaldehyde/Butanol Heat denaturation Centrifugation, Washing, Separation
Aq.Solution of protein/polymer First emulsion (W/O) MICROSPHERES Dispersion in oil/organic phase Homogenization Separation, Washing, Drying Addition of aq. Solution of PVA Addition to large aq. Phase Denaturation/hardening Multiple emulsion Microspheres in solution DOUBLE EMULSION BASED METHOD
When two reactive monomers are dissolved in immiscible solvents, the monomers diffuse to the oil- water interface where they react to form a polymeric membrane that envelopes dispersed phase.
Drug is incorporated either by being dissolved in the polymerization medium or by adsorption onto the nanoparticles after polymerization completed.
The nanoparticle suspension is then purified to remove various stabilizers and surfactants employed for polymerization by ultracentrifugation and re- suspending the particles in an isotonic surfactant-free medium.
PHASE SEPARATION METHOD Aqueous/Organic.Solution of polymer Drug dispersed or dissolved in polymer solution MICROSPHERES Drug Separation, Washing, Drying Hardening Polymer rich globules Microspheres in aq./organic phase
An aqueous phase saturated with electrolytes (e.g., magnesium acetate, magnesium chloride) and containing PVA as a stabilizing and viscosity increasing agent is added under vigorous stirring to an acetone solution of polymer.
In this system, the miscibility of both phases is prevented by the saturation of the aqueous phase with electrolytes, according to a salting-out phenomenon.
The addition of the aqueous phase is continued until a phase inversion occurs and an o/w emulsion is formed
Modified release microspheres of indomethacin were prepared by the emulsion solvent diffusion technique using a synthetic polymer, Acrycoat s100.
Microspheres of diltiazem hydrochloride were formulated using combination of polyethylene glycol 6000 and Eudragit RS 100 and Eudragit RS 100 alone by solvent evaporation and non-solvent addition methods with an aim to prolong its release
One useful discovery made from the research of microspheres is a way to fight cancer on a molecular level. According to Wake Oncologists, "SIR-Spheres microspheres are radioactive polymer spheres that emit beta radiation . Physicians insert a catheter through the groin into the hepatic artery and deliver millions of microspheres directly to the tumor site. The SIR-Spheres microspheres target the liver tumors and spare healthy liver tissue. Approximately 55 physicians in the United States use Sirtex’s SIR-Spheres microspheres in more than 60 medical centers.
The concept of microsphere drug delivery systems offers certain advantages over the conventional drug delivery systems such as controlled and sustained delivery. Apart from that microspheres also allow drug targeting to various systems such as ocular , intranasal , oral and IV route .
Novel technologies like magnetic microspheres, immunomicrospheres offer great advantages and uses than conventional technologies .
Further more in future by combining various other strategies, microspheres will find the central place in novel drug delivery, particularly in diseased cellsorting ,diagnostics, gene and genetic materials, safe,targated and effective invivo delivery which may have implications in gene therapy.
This area of novel drug delivery has innumerable applications and there is a need for more research to be done in this area.