Hormone delivering system

Cascone, M.G., B. Sim and S. Downes, Blends of synthetic and natural polymers as drug deliver) systems for growth hormone. Biomaterials, 16 (1995) 569-574. 

In addition, the contraceptive exemplifies two other values of continuous, controlled delivery. One is the achievement of targeted drug delivery to a single organ (the uterus) of a type of agent (a birth control hormone) that previously had to be delivered system-ically to the whole body. The other is the ability to use—because of continuity of delivery—a biological substance (progesterone)... 

The administration of drugs to ease disease and chronic, severe pain or to provide benefits such as hormone replacement therapy is difficult because drugs taken orally may lose much of their potency in the harsh conditions of the digestive system. In addition, they are distributed throughout the entire body, not just where they are needed, and side effects can be significant. Recently, however, techniques have been developed to deliver drugs gradually over time, to the exact location in the body where they are needed, and even at the time when they are needed. 

Cellular Carriers. Erythrocytes, leukocytes, platelets, islets, hepatocytes, and fibroblasts have all been suggested as potential carriers for drugs and biological substances. They can be used to provide slow release of entrapped drugs in the circulatory system, to deliver drugs to a specific site in the body, as cellular transplants to provide missing enzymes and hormones (in... 

A noteworthy feature of this specialized circulation is that the regulatory hypothalamic hormones are delivered directly to the adenohypophysis by the portal system. Therefore, the concentration of these hormones remains very high because they are not diluted in the blood of the entire systemic circulation. 

The circulatory system carries out many important functions that contribute to homeostasis. It obtains oxygen from the lungs nutrients from the gastrointestinal tract and hormones from the endocrine glands and it delivers these substances to the tissues that need them. Furthermore, it removes metabolic waste products, such as carbon dioxide, lactic acid, and urea, from the tissues. Finally, it contributes to the actions of the immune system by transporting antibodies and leukocytes to areas of infection. Overall, the circulatory system plays a vital role in maintenance of optimal conditions for cell and tissue function. 

Polymeric membrane-based implantable drug delivery systems have been developed to deliver growth hormone, hormonal contraception, and leuprolide for the treatment of prostate cancer. Implanted sialic tubes loaded with lev-onorgestrel Norplant system) is used outside the United States to provide five years of sufficient sustained release of the... 

Though there are no drugs yet on the market from this particular system, the pyridine-pyridinium redox CDS has been widely exploited experimentally to deliver hormones and drugs to the brain (Bodor and Farag, 1984 Shek ef al., 1987). By using a variety of groups, R, in 27 from, for example, methyl through to octyl, the lipophilicity can be adjusted to provide optimum properties for passive transport. 

Other drug-delivery systems may include double emulsions, usually W/O/W, for transporting hydrophilic dmgs such as vaccines, vitamins, enzymes, hormones [441], The multiple emulsion also allows for slow release of the delivered drug and the time-release mechanism can be varied by adjusting the emulsion stability. Conversely, in detoxification (overdose) treatments, the active substance migrates from the outside to the inner phase. 

A simple way to circumvent the problem and improve the control is to use predictive control, often called feed forward. The idea is to use a control signal, CCff, which in some way reflects the expected time-course of CC that is needed to keep CO close to CL In technical systems this control is frequently called model predictive control (MPC [12]), because CCff is typically derived from a mathematical model. In biological systems, the feed forward is mostly delivered by nerve signals, more rarely by hormones. 

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