Controlled release systems administration, routes

Historically, the oral route of administration has been used the most for both conventional and novel drug-delivery systems. There are many obvious reasons for this, not the least of which would include acceptance by the patient and ease of administration. The types of sustained- and controlled-release systems employed for oral administration include virtually every currently known theoretical mechanism for such application. This is because there is more flexibility in dosage design, since constraints, such as sterility and potential damage at the site of administration, axe minimized. Because of this, it is convenient to discuss the different types of dosage forms by using those developed for oral administration as initial examples. 

It is estimated that 90% of all medicines usage is in oral forms and oral products consistently comprise more than half the annual drag delivery market. It is the preferred route of administration, being convenient, controlled by the patient and needs no skilled medical intervention. Considerable success has been achieved with various types of controlled-release systems for peroral delivery, which are used to prolong drag effects. 

J.R. Robinson, V.H. Li, and V.H. Lee, Influence of drug properties and routes of drug administration on the design of sustained and controlled release systems, in Controlled Drug Delivery Fundamentals and Applications, 2nd ed.. New York Marcel Dekker Inc pp. 4-94, 1987. 

Before treating the various classes of sustained- and controlled-release drug-delivery systems in this chapter, it is appropriate to note that drug delivery may be incorporated in other chapters where the various classes of drug products and routes of administration are discussed. In addition, the reader is referred to Chapter 14 on target-oriented drug-delivery systems. 

Sustained- and controlled-release devices for drug delivery in the vaginal and uterine areas are most often for the delivery of contraceptive steroid hormones. The advantages in administration by this route—prolonged release, minimal systemic side effects, and an increase in bioavailability—allow for less total drug than with an oral dose. First-pass metabolism that inactivates many steroid hormones can be avoided [183,184],... 

As pharmaceutical scientists gain experience and tackle the primary challenges of developing stable parenteral formulations of proteins, the horizons continue to expand and novel delivery systems and alternative routes of administration are being sought. The interest in protein drug delivery is reflected by the wealth of literature that covers this topic [150-154]. Typically, protein therapeutics are prepared as sterile products for parenteral administration, but in the past several years, there has been increased interest in pulmonary, oral, transdermal, and controlled-release injectable formulations and many advances have been made. Some of the more promising recent developments are summarized in this section. 

The design of controlled release drug delivery systems should be done with a thorough knowledge of the anatomy and physiology of the route of administration. The different barriers and drug delivery considerations for each route are summarized below. 

Polylactic acid has been studied extensively for controlled release applications ranging from the oral delivery of simple drugs such as indomethacin9 to the parental administration of complex proteins such as insulin.10 Polylactic acid of different molecular weights has been studied as matrix material for parenteral administration. Seki et al.11 used polylactic acid 6000 and Smith and Hunneyball8 used polylactic acid 100,000 for the controlled delivery of drugs by the parenteral route. Several polylactic acid systems have been studied for the controlled... 

This chapter has considered the controlled release of drugs from tablet coating systems. These systems are still the preferred route of drug administration due to... 

Drugs are applied topically primarily for local effects however, this route can be used to administer drugs for systemic action. Few drugs readily penetrate intact skin. The absorption of drugs that do penetrate the skin is proportional to the surface area over which they are applied and to their lipid solubility. Increased cutaneous blood flow also enhances absorption. Systemic toxicity can become evident when highly lipid-soluble substances (e.g. lipid-soluble insecticides) are absorbed through the skin. Controlled-release patches are now commonly used in human medicine for transcutaneous drug administration. 

Keywords Drug delivery systems Targeted drug delivery Nanoparticles Nanobiotechnology Personalized medicine Routes of drug administration Drug delivery devices Controlled release Protein/peptide delivery Drug formulations... 

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