Controlled-release preparation, administration

Dosages and routes of administration Oxycodone is given by mouth in single doses of 5-10 mg or as controlled release preparations with doses of 40 mg (Cairns, 2001). Rectal administration is also possible. Oral formulations often contain combinations with paracetamol or acetylsalicylic acid. 

A controlled release preparation of diclofenac sodium, a non-steroidal anti-inflammatory agent, was developed for transdennal administration. PVAl and PVAl/polyacrylic acid(PAA) alloy membranes were prepared from a solvent-casting technique using different PVAl/PAA v/v ratios. The release of the drug from the membrane was evaluated under in viti o conditions at pH 7.4. The delivery system provided linear release without time lag, burst effect and boundary layer resistance. The effects of such variables as film thickness and PVAl/PAA ratio on the permeation behaviour of the polymeric membranes are discussed. The optimal PVAl/PAA was found to be 50/ 50. 48 refs. 

For many drug delivery applications, the preferred method of delivery of the dosage form is by injection. For controlled release applications, the most frequently used approach to allow this method of administration is to prepare microspheres of the polymer containing the drug to be delivered. Several different techniques have been developed for the preparation of microspheres from polyanhydrides. 

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. 

Chronic effects of administration of cannabinoids have been studied in slices prepared from 40-day-old rats born to mothers who received daily subcutaneous injections of WlN55,212-2 throughout gestation (Mereu et al. 2003). LTP in these slices was reduced as compared to control slices prepared from rats born to untreated mothers. The slices also showed impaired basal and K+ -stimulated glutamate release. 

Drug release should be controlled in accordance with the therapeutic purposes and pharmacological properties of the active substances. The plasma drug levels-time profiles after oral administration can be classified as ratetime-controlled release. Rate-controlled release is further classified into three types, i.e. immediate-release, prolonged-release, and modified-release. One typical time-controlled release is delayed-release. More advanced releases can be achieved by combinations of these different release types (Fig. 14.9). Various CyD derivatives have been used in order to modify drug releases in oral preparations [13, 15]. 

Reslow M, Bjorn S, Drustrup J, Gustafsson NO, Jonsson M, Laakso T. A controlled-release, parenter-ally administrable microparticle preparation. EU patent 1328258, 2008. 

Despite the well known advantages of controlled release dosage forms, conventional dosage forms are still most widely used probably because they cost less to manufacture. More than three quarters of all drug formulations are made for oral administration. Oral dosage forms such as tablets, capsules, and liquids are still most popular. Since tablet is one of the most widely used dosage forms and its preparation requires incorporation of polymers, we will focus on polymers used in tableting process. 

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