Oral drug administration routes, limitations

Hydrophobic polymers are often used to deliver biomacromolecules regardless of the route of administration. The rapid transit time of approximately 8 hours limits the time of a device in the gastrointestinal (GI) system, consequently the mechanisms possible for oral drug release are limited. The predominant method of release from hydrophobic polymers has been degradation, or biodegradation, of a polymeric matrix by hydrolysis (Figure 11.1). In fact, all of the hydrophobic polymers described in this chapter for use as oral protein or peptide delivery are hydrolytically unstable. 

Oral Delivery Systems. The oral route of drug administration has been the most popular one, however, it is not without problems and constrains. First of all, the total gastrointestinal residence time limits the time frame or "window" for oral absorption. The... 

One of the key pieces to development of a successful drug product is the ability to deliver the drug to the site of action with minimal discomfort or inconvenience to the patient. For small molecule therapeutics, there is a wide range of options available for drug administration. Delivery via injection (IV, IM, and SC), oral, nasal, ocular, transmucosal (buccal, vaginal, and rectal), and transdermal routes is possible with small molecule drugs. However, the size of proteins and the complexity of their structures severely limit the routes of administration available to proteins. 

Historically, the oral route of drug administration has been the one nsed most for both conventional as well as novel drug delivery. The reasons for this preference are obvious because of the ease of administration and widespread acceptance by patients. Major limitations of oral route of drug administration are as follows ... 

Parenteral (injected) administration of drugs provides a solution to many problems associated with the oral delivery route. A drug injected into the blood circulation is considered to be completely bioavail-able thaefore, the quantity of the surfactants and otha inactive excipients in intravenous dosage forms are usually strictly limited. The most common alternative routes of parenteral drug administration are intramuscular or subcutaneous injections [2], Several otha injection routes are available to elicit rapid local reaction, such as intrathecal, intraarticular, and intracardiac. 

Liposomes as a dosage form allow for a broad variety of administration routes. In addition to the most traditional and frequent parenteral (intravenous) way of administration, some alternative approaches are also developed or under development, although each of these approaches has its own problems and limitations. Thus, oral administration requires high liposome stability and drug delivery from the gut to the blood with subsequent drug release. Early attempts with polymerized liposomes as potential oral vaccine carriers were only partially successful. Currently, many alternative schemes are under development. 

The occnrrence of a mucus layer that present at the surface of various organs has been exploited to develop mucoadhesive dosage forms. These layers act as administration site to prolong time, and increase the local and/or systemic bioavailability of the administered drug [58]. The appearance of micro and nanotechnologies simultaneously with the execution of non-invasive and painless administration routes has transforms the pharmaceutical market and the management of disease. Intending to minimize the chief limitations of the oral route and... 

Eritadenine is approximately ten times as potent as clofibrate in rats. Dietary hypercholesterolemia was suppressed by eritadenine but limited effects on Triton-induced hyperlipidemia were observed. The oral route of administration appears to produce superior lipid reductions and the drug causes a limited but significant enhancement in the rate of removal of cholesterol from the plasma compartment.65... 

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