Drug delivery systems oral dosage forms

Vollmer U, Galfetti P. RapidFilm oral thin films (OTF) as an innovative drug delivery system and dosage form. Drug Delivery Report Spring/Summer 2006. 

According to the online resource, Pharmacircle, 53% of all commercialized pharmaceutical dosage forms are oral drug-delivery systems. Oral drug delivery is the most common route of administration due to the fact that it is more convenient, less invasive, and less painful compared to other routes of administration. Of the various oral drug-delivery systems shown in Figures 27.1 and 27.2, 68% are tablets and 20% are capsules. In particular, tablets are relatively easy to manufacture and are generally well-accepted by patients. 

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. 

Drug-delivery systems are essentially specialized dosage forms developed to overcome the limitations of conventional dosage forms, such as simple tablets, capsules, injectable solutions, etc. Some of the reasons behind the development of oral DDSs are listed below ... 

Excellent accessibility to the buccal mucosa makes application of the dosage form painless. It ean be preeisely loeated, and is easily removed without diseomfort at the end. The oral cavity consists of a pair of buccal mucosae. Hence, a drug delivery system can be applied at various sites, on the same mucosa or on the left or right buccal mucosa on different applications. This is particularly advantageous if the delivery system contains a drug or excipient whieh mildly and reversibly damages or irritates the mucosa. 

A buccal drug delivery system is applied to a specific area on the buccal membrane. Moreover, the delivery system ean be designed to be unidirectional in drug release so that it can be protected from the loeal environment of the oral cavity. It also permits the inclusion of a permeation enhancer/protease inhibitor or pH modifier in the formulation to modulate the membrane or the tablet-mucosal environment at that particular application site. While the irritation is limited to the well-defined area, the systemic toxicity of these enhancers/inhibitors and modifiers can be reduced. The buccal mucosa is well suited for this type of modification as it is less prone to irreversible damage [9]. In the event of drug toxicity, delivery can be terminated promptly by removal of the dosage form. 

There are few occasions where a drug is delivered alone in a pure form into the body, but it is usually combined with other materials (called excipients) to form drug delivery systems ( medicines , formulations or dosage forms ). These promote accurate dosing, therapeutic effectiveness, stability and patient acceptability. By far the most common route for delivering drugs into the body is by the oral route, swallowing a tablet or capsule. 

Solid oral dosage forms containing new chemical entities (NCEs) are commonly formulated into tablets or capsules as their first market image formulation. Subsequent drug product line extension development on these NCEs may evaluate more specialized drug delivery systems. Dissolution testing of standard oral tablets or capsules will commonly utilize the paddle or basket apparatus. In this chapter we focus primarily on the development and subsequent validation of dissolution testing methods that use these two devices. 

Another example of an excipient-excipient interaction that can be used to our advantage is the one between xanthan gum and locust bean gum (carob gum or cer-atonia) in the presence of water. This interaction forms the basis of the identification test for Xanthan Gum NF. The interaction creates a much more viscous gel system than can be created using either component alone. This has been used in the formulation of controlled release oral solid dosage forms in the TimeRx drug delivery system (11). 

Self-emulsifying drug delivery systems are oral dosage forms consisting of drug, oils, surfactants, and sometimes cosolvents (Constantinides, 1995 Pouton, 1997 Pouton, 2000). On addition to water... 

A major problem associated with classic oral sustained release drug delivery is the uncertainty of location, and hence environment, of the drug-dosage form at any point in time following ingestion. Therefore, it is important to understand the possible implications of GI motility on the location of drug delivery systems in the GI tract under various physiological conditions. 

V. H. L. Lee and J. R. Robinson. Methods to achieve sustained drug delivery The physical approach Oral and parenteral dosage forms, in J. R. Robinson (ed.), Drugs and the Pharmaceutical Sciences, Vol. 6 Sustained and Controlled Release Drug Delivery Systems, 3d ed. New York Marcel Dekker, 1978, pp. 123—173. 

Khan GM. Controlled release oral dosage forms some recent advances in matrix type drug delivery systems. Sciences 2001 ... 

Carbopol resins also have been used in controlled-release dosage forms. Especially, the resins Noven AA-1 USP and Carbopol 934P NF are being extensively developed in bioadhesive drug delivery systems for topical, bucal or nasal, ocular, and rectal applications (e.g., Fentanyl ). Noven CA-1 USP and CA-2 USP are used as oral laxative and antidiarrheal products in swallowable and chewable tablets. 

Comparative pharmacokinetic profiles of nifedipine delivered from Procardia XL, an osmotic pressure-controlled drug delivery system, once-a-day versus that from Procardia, an immediate-release dosage form, taken on time 0, 8 and 16 in human volunteers. Modified from Y.W. Chien. Oral drug delivery and delivery systems. Y.W.Chien (ed.) (1992) Novel Drug Delivery Systems. Marcel Dekker, Inc. New York, pp. 139-196... 

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