CONTROLLED DRUG DELIVERY SYSTEMS

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CONTROLLED DRUG DELIVERY SYSTEMS:

CONTROLLED DRUG DELIVERY SYSTEMS Submitted by: K.V.V.S.Narayana Reddy Dept of pharmaceutics Toxicity level Injection Controlled release Therapeutic Level Time

HISTORY:

HISTORY Wurster technique 1949 Coacervation (liquid encapsulation) 1953 Mircroencapsulation 1960’s Implants 1970’s Transdermal 1980’s Site directed systems 1990’s

Why controlled drug delivery ?:

Why controlled drug delivery ? In general most of the pharmaceutical industries existence, drug delivery induced simple, fast-acting responses(conventional forms) via oral or injection delivery routes Problems associated with this approach: Reduced potencies because of partial degradation( 1 st pass metabolism) Toxic levels of administration( if excess dose) Increase costs associated with excess dosing Compliance issue due to administration pain

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As the cost and complexity of individual drug molecules has risen the problems with the classical delivery strategies over took their benefits. Goal of more sophisticated drug delivery techniques Deliver exactly to a target site to limit side effects distribute drugs through specific areas of the body without degradation Maintain a therapeutic drug level for prolonged periods of time 4.Predictable controllable release rates 5.Reduce dosing frequency so increasing patient compliance Toxicity level Injection Controlled release Therapeutic Level Time

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ADVANTAGES DISADVANTAGES Total dose is low. Dose dumping. Reduced GI side effects. Reduced potential for accurate dose adjustment. Reduced dosing frequency. Need of additional patient education Better patient acceptance and compliance. Stability problem Less fluctuation at plasma drug levels. More uniform drug effect Improved efficacy/safety ratio.

CLASSIFICATION:

CLASSIFICATION Dissolution Controlled Release Diffusion Controlled Release Diffusion & Dissolution Controlled Release System Ion- exchange Resins pH- Independent Formulations Osmotically Controlled Release Altered Density Formulations

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Osmotic core containing drug Drug solution Rigid semi permeable membrane Systems in controlled drug delivery Flexible membrane In type A drug containing a solid core together with electrolyte which is dissolving by the incoming water, the electrolyte provides high osmotic pressure difference. In second system the drug is in solution with a semi permeable membrane, and the electrolyte surrounds the bag both systems have single or multiple holes bored through the membrane to allow the drug release Similarly high osmotic pressure required to pump the drug in 1 st system and compression of membrane in second system. Type A Type B Osmotic core with out drug

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DISSOLUTION: in chemistry, the process of dissolving a solid substance into a solvent to make a solution DIFFUSION: Diffusion describes the spread of particles through random motion from regions of higher concentration to regions of lower concentration.

TWO TYPES OF DISSOLUTION CONTROLLED SYSTEMS:

TWO TYPES OF DISSOLUTION CONTROLLED SYSTEMS DISSOLVING COAT DRUG LAYER VARIOUS THICKNESS OF DISSOLVING COAT SINGLE BEAD TYPE DEVICE BEADS CONTAINING DRUG WITH DIFFERENT THICKNESS OF DOSSOLVING COATS

dc/dt= dissolution rate kD= dissolution rate constant D= diffusion coefficient Cs= saturation solubility of the solid c=concentration of the solute in bulk solution:

dc/ dt = dissolution rate k D = dissolution rate constant D= diffusion coefficient Cs= saturation solubility of the solid c=concentration of the solute in bulk solution The dissolution process in steady state is described by Noyes- whitney equation: dc dt k D A(c s -c) A(c s -c) D h

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PRODUCT ACTIVE INGREDIENTS MANUFACTURER ORNADE SPANSULES PHENYLPROPANOLAMINE HYDROCHLORIDE SMITH KLINE BEECHAM DIAMOX SEQUELS ACETAZOLAMIDE LEDERLE NICOBID TEMPLES NICOTINIC ACID RORER PRNTRITOL TEMPLES PENTAERYTHRIOTL RORER POLARAMINENREPETABS DEXCHLORPHENIRAMINE SCHERING ENCAPSULATED DISSOLUTION PRODUCTS MATRIX DISSOLUTION PRODUCTS PRODUCT ACTIVE INGREDIENTS MANUFACTURER DIMETANE EXTENTABS BROMPHENIRAMINE ROBINS QUINIDEX EXTENTABS QUINIDINE SULPHATE ROBINS MESTINON TIMESPANS PYRIDOSTIGMINE BROMIDE ICN TENUATE CHRONOTABS DIETHYLPROPION HCL MERREL

DIFFUSIONAL SYSTEMS:

DIFFUSIONAL SYSTEMS Diffusional systems are characterized by the release rate of a drug being dependent on its diffusion through an inert membrane barrier. Usually this barrier is an insoluble polymer It is classified in to 2 types: Reservoir devices Matrix devices RESERVOIR DEVICES Reservoir devices are characterised by a core of drug, the reservoir is sorrounded by a polymeric membrane. The nature of the membrane determines the rate of release of drug from the system. The process of diffusion is generally described by a series of equations that were first detailed by FICKS : J= -D dc/ dx

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Where D = is the diffusion coefficient of the drug. dc/ dx = is the rate of change in concentration C relative to a distance X in the membrane. Drug reservoir Membrane membrane C m(o) C m(d) d C (d) C (o) C m(o) & C m(d) = represents concentrations of drug at inside surfaces of the membrane. C (o) & C (d) = represents concentrations of drug in the adjacent regions. d = is the thickness of the diffusion layer It is usefull to make the assumption that the drug on either side of the membrane is in equilibrium with its respective membrane surface, so the concentration just inside the membrane surface can be related to the concentration in the adjacent region by the following equations: K= C m(o) / C (d) at x=0 K= C m(d) /C (d) at x=d K Is the partition coeffecient

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ADVANTAGES OF RESERVOIR DIFFUSIONAL SYSTEMS: zero order delivery is possible. release rate variable with polymer type. DISADVANTAGES: System must be physically removed from implant sites. Difficult to deliver high molecular weight compounds. Potentially toxic if system fails. Product Active ingredient Manufacturer Nico-400 Nicotinic acid Jones Nitro-bid Nitroglycerin Marion Cerespan Papaverine hydrochloride rorer RESERVOIR DIFFUSIONAL PRODUCTS

MATRIX DEVICES:

MATRIX DEVICES In matrix devices drug is dispersed homogeneously through out a polymer matrix. In this model drug in the out side layer exposed to the bathing solution is dissolved first and then diffuses out of the matrix, this process continues with the interface between the bathing solution and the solid drug moving towards the interior. So for this system to be diffusion-controlled, the rate of dissolution of drug particles with in the matrix must be much faster that the diffusion rate of dissolved drug leaving the matrix. Drug dispersed in polymer polymer

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Derivation of the mathematical model to describe this system involves the following assumptions: A pseudo-steady state is maintained during drug release. The diameter of the drug particles is less than the average distance of drug diffusion through the matrix. The bathing solution provides sink conditions at all times. The diffusion coefficient of drug in the matrix remains constant. The equation which describes the rate of release of drugs dispersed in an inert matrix system have been derived by HIGUCHI. dM dh = C o dh - C s /2 dM = change in the amount of drug released per unit area dh = change in the thickness of the zone of matrix that has been depleted of drug Co = total amount of drug in a unit volume of matrix Cs = saturated concentration of the drug with in the matrix.

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ADVANTAGES: Easier to produce than reservoir devices. Can deliver high molecular weight compounds DISADVANTAGES: Cannot obtain zero-order release Removal of remaining matrix is necessary for implanted systems. MATRIX DIFFUSIONAL PRODUCTS Product Active ingredient Manufacturer Desoxyn-gradumet Methamphetamine hydrochloride Abbott Fero-gradumet Ferrous sulfate Abbott

COMBINATION OF DIFFUSION AND DISSOLUTION:

COMBINATION OF DIFFUSION AND DISSOLUTION It is type of swelling controlled system Here the drug is dissolved in the polymer, but instead of an insoluble polymer, as in previous systems, swelling of the polymer occurs. This allow entrance of water, which causes dissolution of the drug and diffusion out of the swollen matrix. In these systems the release rate is highly dependent on the polymer-swelling rate, drug solubility , and the amount of soluble fraction in the matrix. This system usually minimizes burst effects, since polymer swelling must occur before drug release.

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