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Komal R. Nikam*et al. /International Journal Of Pharmacy&Technology ISSN: 0975-766X CODEN: IJPTFI Available through Online Review Article www.ijptonline.com NOVEL TRENDS IN PARENTERAL DRUG DELIVERY SYSTEM: REVIEW Komal R. Nikam *, Mahendra G. Pawar, Shivraj P. Jadhav, Vinod A. Bairagi Department of Pharmaceutics, K.B.H.S.S.T’s College of Pharmacy, Malegaon- 423105, Maharashtra, (India) Email: [email protected] Received on 09-05-2013 Accepted on 22-05-2013 Abstract Drug with narrow therapeutic index, poor bioavailability are generally given by parenteral route which is effective one in case of unconsciousness, nausea, in emergency clinical episodes. To maintain a therapeutic effective concentration of the drug, it requires frequent injections which ultimately lead to patient discomfort. But parenteral route offers rapid onset of action with rapid declines of systemic drug level. So to provide a targeted and sustained release of drug in predictable manner major progress has been done in the field of formulation technologies. This article explore various prolonged release parenteral drug delivery system and their strategies of preparation, potential benefits, drawbacks and in-vitro testing methods. Key Words: Parenteral, Sustained, therapeutic index, targeted. Introduction Parenteral preparations are sterile preparations intended for administration by injection, infusion or implantation into the human or animal body. Parenteral preparations may require the use of excipients 1, for example: To make the preparation isotonic with respect to blood, To adjust the pH, to increase solubility, To prevent deterioration of the active substances or To provide adequate antimicrobial properties, but not to adversely affect the intended medicinal action of the preparation or, at the concentrations used, to cause toxicity or undue local irritation. A number of technological advances have been made in the area of parenteral drug delivery, leading to the development of sophisticated systems that allow drug targeting and the sustained or controlled release of parenteral medicines 2. IJPT | July-2013 | Vol. 5 | Issue No.2 | 2549-2577 Page 2549 Komal R. Nikam*et al. /International Journal Of Pharmacy&Technology Parenteral formulations by intravascular route offer exclusive opportunity for direct access to the bloodstream and rapid onset of drug action as well as target to specific organ and tissue sites 3. This review article mainly focus on recent advances in parenteral drug delivery system with its implementation in pharmaceutical field. We have made discussion on injectables, implants and infusion devices which are classified as shown in figure 1. Figure 1: Classification of Parenteral Drug Delivery. IJPT | July-2013 | Vol. 5 | Issue No.2 | 2549-2577 Page 2550 Komal R. Nikam*et al. /International Journal Of Pharmacy&Technology I. Injectable: Injections are sterile solutions, emulsions or suspensions. They are prepared by dissolving, emulsifying or suspending the active substance(s) and any added excipients in water, in a suitable non-aqueous liquid, that may be non-sterile where justified, or in a mixture of these vehicles 4. The most commonly used approaches are as follows 5. 1) Use of viscous, water miscible vehicles such as an aqueous solution of gelatin or poly vinyl pyrrolidine. 2) Use of water immiscible vehicles such as vegetable oil plus water repelling agent such as aluminium mono stearate. 3) Formation of thixotropic suspensions 4) Preparation of water insoluble drug derivatives such as salts, complexes and esters etc. 5) Dispersion in polymeric micro spheres or microcapsules such as lactide glycolide homopolymer or copolymers. 1) Injectable Controlled Release Formulation: The injectable depot formulation was developed with the primary objective of simulating the continuous drug administration of IV infusion. It often results in reduced drug dose, decreased side effects, enhanced patient compliance and improved drug utilization 6. Reasons for development of Parenteral Depot System (PDS) 7: No surgical removal of depleted system is required as it is metabolized in non toxicological by product. The drug release from this system can be controlled by Diffusion of drug through the polymer, Erosion of the polymer surface with concomitant release of physically entrapped drug, Cleavage of covalent bond between the polymer bulks or at the surface followed by diffusional drug loss. Depot formulation may be classified on the basis of the process used for controlled drug release as follows 6, 8: i. Dissolution controlled depot formulation ii. Adsorption type depot formulation iii. Encapsulation type depot formulation iv. Esterfication type depot formulation IJPT | July-2013 | Vol. 5 | Issue No.2 | 2549-2577 Page 2551 Komal R. Nikam*et al. /International Journal Of Pharmacy&Technology i) Dissolution controlled depot formulation In this depot formulation the rate of absorption is controlled by the slow dissolution of drug particles in the tissue fluid surrounding the formulation. The rate of dissolution (Q/t) d under sink condition is defined by: (Q/t) d = SA.ds.Cs/Hd Where SA = surface area of the drug particles in contact with the medium ds= is the diffusion coefficient of drug molecules in the medium Cs=is the saturation solubility of the drug in the medium. Hd = thickness of the hydrodynamic diffusion layer surrounding each drug particle. Basically two approaches like complex or salt formation and suspension form of drug control the dissolution of drug to prolong the absorption and hence the therapeutic activity of the drug. A] Formation of salt or complexes with low aqueous solubility: Some examples of this type of formulation include Penicillin G procaine, penicillin G benzathine, Naloxone pamoate and naltrexone Zn tannate. All these produces prolonged therapeutic activites. B] Aqueous Suspension: Suspension of macro crystals are known to dissolve more slowly than small crystals this is called macro crystal principle and can be applied to control the rate of drug dissolution e.g.: aqueous suspension of testosterone isobutyrate for I.M injection in contrast with the suspension in plain peanut oil i.e. without gelation with aluminium monostearate or with aqueous suspension this macrocrystal principle was followed fairly well. Its prolonged action is partly because these thixotropic suspensions tend to form compact and cohesive depots at the site of intramuscular injection. This leads to slow release and partly because of the low aqueous solubility. ii) Adsorption type depot formulation: Here drug molecule is bind to adsorbents, free species of the drug is available for adsorption as soon as the unbound drug molecules are adsorbed a fraction of the bound drug molecule is released to maintain equilibrium 9. E.g. vaccine preparations in which the antigens are bound to highly dispersed aluminium hydroxide gel to sustain their release and hence prolong the duration of stimulation of antibody formation. Other examples include insulin-Zn-Protein complex, isophane insulin suspension and Gliobin-Zn-insulin injection USP. IJPT | July-2013 | Vol. 5 | Issue No.2 | 2549-2577 Page 2552 Komal R. Nikam*et al. /International Journal Of Pharmacy&Technology iii) Encapsulation-type depot preparations: This type of preparation is prepared by encapsulating drug solids within a permeation barrier or dispersing drug particles in a diffusion matrix. The release of drug is controlled by the rate of permeation across the permeation barrier and the rate of biodegradation of the barrier macromolecules. Both permeation barrier and diffusion matrix are fabricated from biodegradable or bioabsorbable macromolecules, such as gelatin, dextran, polylacticacid, lactide-glycolide copolymers, phospholipids, long-chain fatty acids and glycerides. Typical examples are naltrexone pamoate-releasing biodegradable microcapsule, liposomes, and norethindrone- releasing biodegradable lactide-glycolide copolymer beads. iv)Esterification-type depot preparations: This depot preparation is prepared by esterifying a drug to form a bioconvertible prodrug-type ester and then formulating it in an Injectable formulation. This chemical approach depends upon number of enzyme (esterase) present at the injection site. This formulation forms a drug reservoir at the site of Injection. The rate of drug absorption is controlled by the interfacial partitioning of drug esters from the reservoir to the tissue fluid and the rate of bioconversion of drug esters to regenerate active drug molecules. It is exemplified by the fluphenazine enanthate, nandrolone decanoate in oleaginous solution. 2) Colloidal Dispersions i) Liposomes: Liposomes are formed by the self-assembly of phospholipid molecules in an aqueous environment as shown figure 2. Figure 2: Structure of Liposome The amphiphilic phospholipid molecules form a closed bilayer vessicle in an attempt to shield their hydrophobic groups from the aqueous environment while still maintaining contact with the aqueous phase via the hydrophilic head group 10 . IJPT | July-2013 | Vol. 5 | Issue No.2 | 2549-2577 Page 2553 Komal R. Nikam*et al. /International Journal Of Pharmacy&Technology Different methods of preparation are as following 11: Sonication High pressure homoginization Detergent dialysis Lipid – alcohol - water injection Reverse phase evaporation Dehydration – rehydration Applications: In Cancer Therapy: As liposomes are rapidly cleared from the circulation and largely taken up by the liver macrophages 12 there use in cancer therapy