25-06-2013, 03:55 PM
TARGETED DRUG DELIVERY SYSTEM
TARGETED DRUG.pptx (Size: 1.12 MB / Downloads: 71)
INTRODUCTION:
DRUG DELIVERY is a special form of drug delivery system where the pharmacologically active agent or medicament is selectively targeted or delivered only to its site of action or absorption and not to the non-target organs or tissues or cells. The drug may be delivered
To the capillary bed of the active sites,
To the specific type of cell (or) even an intracellular region. Ex- tumour cells but not to normal cells,
To a specific organ (or) tissues by complexing with the carrier that recognizes the target
REASON FOR DRUG TARGETING:
In the treatment or prevention or diseases.
Pharmaceutical drug instability in conventional dosage form solubility ,biopharmaceutical low absorption, high-membrane bounding, biological instability, pharmacokinetic / pharmacodynamic short halflife, large volume of distribution, low specificity, clinical, low therapeutic index.
CONCEPT AND COMPONENTS OF TDDS
Targeting of drugs to special cells and tissues of the body without their becoming a part of systemic circulation is a very novel idea. If a drug can be administered in a form such that it reaches the receptor sites in sufficient concentration without disturbing in extraneous tissue cells.
Such products are prepared by considering-
1.specific properties of target cells.
2.nature of markers or transport carriers or vehicles, which convey drug to specific receptors.
3.ligands and physically modulated components.
MAGNETIC MICROSPHERES:-
These are the microspheres containing substance inside which can be easily targeted by applying external magnetic field.
Magnetic microspheres were developed:
a)To minimize renal clearance
b) To increase target site specificity
c) To entrap a wide variety of drugs
d) In the entrapment of localised tumours in the religions of well defined blood supply
e) For controlled release of peptide protein drugs such as LHRH, which have the short half life and otherwise need to be injected once or more daily as conventional parenteral formulation.
f)To minimize reticulo endothelial clearance target site specificity.
IMPORTANT CHARACTERISTICS OF MICROSPHERES & MAGNETIC MICROSPHERES:
Particle size of a drug carrier can affect the degree of drug entrapment.
Increase in size of the albumin microspheres due to the hydration can alter its body distribution.
Use of sub-micron size microspheres minimises the incidence of pulmonary embolism that often encounters with particles greater than 7µm or particles which aggregate upon their vivo administration.
The retention of magnetic microspheres at the target site is dependent on the “magnetic content” of the carrier & the magnitude of the “applied magnetic field”.
Although high magnetic content allows the use of smaller magnetic fields, it reduces the effective space available within the carrier for the drug entrapment.
In targeting using MM, the magnetic field content of the carrier & the magnitude of applied magnetic field are important.
INTRACELLULAR TARGETING:
Certain cytotoxic drugs are active intracellular, but are normally discarded due to their poor intracellular influx.
The poor efficacy of many therapeutic substances for intracellular bacterial & parasitic therapy is known.
The intracellular delivery of the drugs by suitable means can obviate these problems.
For e.g. the biologically active streptomycin was released from albumin microspheres inside the phagocytic cells after ingestion and intracellular degradation of microspheres.