KEY CONCEPTS IN DRUG DELIVERY

Some drugs may pass through the body easily, while others are protein binding and transporters influence drug distribution. if the drug is highly protein bound, they are stuck to the blood stream. if the drug is very potent, it. membranes have transporters. some drugs look like endogenous substances. Blood-brain barrier cannot cross into the brain. the mode of administration determines whether the drug reaches its site. some compounds are turned reactive to enable effectively. UDP glycosyl transferase, n-acetyl transferase and monoamine oxidase are major drug metabolism pathways. cytochrome p450 enzyme--is a common pathway for metabolizing drugs. these enzymes differ from person to person. same dose of drug, differing levels of activity.

Liposomes are spherical envelops created by mixing phospholipids and cholesterol. Lipids gradually diffuse into the bodily fluid where the membrane envelop breaks and releases the drug. Liposomes are used in slow drug release, targeting the drug and minimizing toxicity.

Nanospheres are submicroscopic particles (10--1000nm) which cross through the GI tract because of their small size. They are made up of a variety of polymers, such as, Poly Methyl Methacrylate (PMMA), Polyethylene or Silica (silicon dioxide). Nanospheres are colloidal systems that entrap therapeutic agents within a colloidal matrix, or are attached to the particle surface by adsorption or conjugation processes. Different synthetic and natural materials are used to prepare these particles. These polymers are biodegradable, being degraded in vivo and eliminated by physiological metabolic pathways; therefore, they could be considered a useful strategy for human applications.

Moreover, these polymeric particles have attractive advantages, for instance sustained and controlled drug release over the time can be obtained and, in some cases, they are able to favor the transport of different GFs across the BBB.