for drug with high dose, with mixture of a drug/cyclodextrin Complex isproblematic, eg, paracetamol. The same phenomenon can also beemployed for the osmotic systems · Use of Swell-able polymers:Polyethylene oxide, vinyl acetatecopolymer have even swelling rate which causes drug release at constant rate.Also, the pressure build up while swelling doesnot rupture the system · Use of wicking agents: Theseagents may improve the surface area of drug along with aqueous fluids.
E.g.Sodium lauryl sulfate and colloidal silicon dioxide, etc.
Ensotrol® technology works on the same principle for drugadministration via osmotic system.· Use of effervescent mixture: It can be new tactic to deliver poorly water-soluble drugsfrom osmotic delivery systems. After administration, the effervescent mixture having drug is deliveredunder pressure via delivery hole in the membrane Effervescent mixture of citric acid and sodium bicarbonate produces carbondi-oxide which build up pressure in the osmotic system and finally release the drug at steady rate · Co-compression of drug with excipients: Different excipients can beused to alter the solubility of drugs with mechanisms likesaturation solubility, pH dependentsolubility. For instance, such excipients are organic acids, buffering agent, etc. · Useof alternative salt form: Change in salt form of drug may improve solubility. It is observed that the salt of drug is too soluble to maintain a saturated solution and thus zero order release for the estimated delivery life ofdosage form. Afterwards osmotic pump is designed with this salt form that give extendedrelease up to 24 h.· Resin Modulation approach:Ion-exchange resin methods are frequently used to alter the solubility ofdrugs.
Some of the resins used in osmotic systems are Poly (4-vinyl pyridine), Pentaerythritol, citric and adipic acids. Classification of OsmoticDDS Osmotic DrugDelivery Devices fall in two categories: · Implantable:1 Implantable osmotic pump2 Oral osmotic Pump 1.Implantable osmotic pump 2 Oral osmotic pump A )Single chamber osmotic pump: B).Multi chamber osmotic pump C) Modified osmotic pump 1. Oral osmotic pump A. the Roseand Nelson pump: Origin: This drug delivery system was initially designed by the Australian scientists Rose and Nelson, in1955 when they were administering drug to the sheep and cattle gut Components This drug delivery system contains three chambers 1 .Drug chamber 2.
Salt chamber holding salt bridge 3. Water chamber 4. Semi permeable membrane Working Semipermeable divides thesalt and water compartment as the water enters from water tosalt chamber due to gradient build up by osmotic pressure the salt chamber extends and forcesthe drug chamber . Drug coms out of the orificeand finally pumped from the DDS to the diseased area. B. Higuchi Leeper osmotic pump This DDS is the advancement of Rose and Nelson pump, in itsdesign in a way that ithas no waterchamber.
Components 1 Saltchamber 2 Drug chamber3 Semi permeable membrane 4 A rigidhousing Working As is has no water chamber so throughthe of imbibition method drug enters thesystem and activates it .On implantation ofdevice the biologicalliquid present in the environment enters the salt chamber whichcomprises of thefluid solution, on enteringbiological fluid absorbs MgSO4 and build up aosmotic pressure that in turn forces the movable partition towards drug chamber and drug comesout of theorifice Modification Through this systempulsatile deliveryis accomplished . Pressure is the critical factor.
This is done by drilling the orificewith stretching elastic material upto the specific concentrationpressure build up open the orifice and drug is deliveredone more time after drug release pressure reduces and orifice getclosed. Application: This system is employed