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Introduction Colloid drug delivery systems CDDSs are vesicular dosage forms They include liposomes niosomes nanospheres and nanocapsules Their size avoids any risk of embolism following intravenous injection CDDSs were initially designed and were studied as drug carriers for targeting purposes The assumption was the expected ability of CDDSs to concert the drug at the therapeutic target andor divert if from the toxicological one Some interesting results have been obtained with drugs possessing a narrow therapeutic margin such as anticancer drugs In addition CDDSs were shown to be able to act as sustained-release dosage forms when injected subcutaneously However the oral route of administration has the advantage of conveniences versatility and safety and is preferred whenever the physicochemical properties of a drug allow adequate bioavailability Many drugs are rendered ineffective after oral administration because of their chemical ability or susceptibility to enzymes in the GI tract or because of their hydrophilic character and ionizability at various pH values or because of their high Mr or Insolubility So CDDs could be able to protect drugs from GI degradation Candidate drugs for entrapment in CDDS could be peptides hormones enzymes clotting factors etc for example all of which exhibit poor oral bioavailability Since the discovery of liposomes in the 60s most of the studies involving CDDSs have examined parenteral routes Their use as oral delivery systems only began in the 70s and has not been completely investigated Furthermore nano-spheres and nanocapsules were developed as more promising tools Niosomes themselves are unilamellar or multilamellar vesicles which are analogues of liposomes Niosomes are formed mainly by self-assembly of synthetic non-ionic surfactants with the optional combination of cholesterol and charged surfactants The ability to entrap solutes allows them to be used as drug carriers The fact that they are made of bilayer membranes allows them like liposomes to be used as model cells observing their response to osmotic gradients membrane phase behaviour and membrane permeability for example The characteristics of
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