I am going to ask about drug delivery system. I would like to know when the drug travels in the blood stream, How much of drug will lose because of enzym in blood stream. It is good to protect drug from blood environment.

I believe it is all dependent upon the type of drug, narcotic vs antibiotic and what the drug is used for, pleasure, infection, etc.

Can you elaborate?

Yes, it depends on the type of drug. Nearly all drugs take effect on their target tissue by first traveling through the blood stream. The rate at which the drug enters the bloodstream depends on the route of administration and the chemical structure of the drug. If it is taken orally then it enters the blood through the gastrointestinal tract and its rate of uptake depends on the rate at which it passes through the epithelial lining of the gut (cells or extracellular matrix proteins). If it is delivered through the skin (transdermal) the rate of uptake into the blood will depend on the rate the drug diffuses through the epithelium of the skin and into the capillaries of the skin. Also, drug can simply be directly injected into the bloodstream. There are other mechanisms used to 'force' drug into the bloodstream such as electroporation. Once in the circulatory system, drug will interact with proteins and enzymes in the blood and eventually be taken to the target tissue, liver, kidneys, or non-target tissues where it is metabolized and eventually excreted through the urine. The entire process is called: absorption/administration, distribution, metabolism and excretion/elimination or ADME for short. It is all very dependent on the chemical nature of the drug.

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