Advantages And Disadvantages Of Controlled Release

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Figure. No.4: Plasma concentration vs time profile of a controlled release form.
 This means that they are actually controlling the drug concentration in the body, not just the release of the drug from the dosage form, as is the case in a sustained-release system.
 Another difference between sustained and controlled-release is that the former are basically restricted to oral dosage forms while controlled-release systems are used in routes like transdermal, oral and vaginal administration.
 Periodic administration of a drug by conventional means, such as taking a tablet every four hours, can result in constantly changing systemic drug concentrations with alternating periods of ineffectiveness and toxicity. Controlled release systems attempt to maintain a therapeutic concentration of a drug in the body for an extended time by controlling the rate of delivery of the drug.
 Controlled-release systems are not necessarily target-specific, which means that they do not ‘exclusively’ deliver the drug to the target organ. This may be achieved by so-called targeted delivery systems which aim to exploit the characteristics of the drug carrier and the drug target to control the bio-distribution of the drug.
Disadvantages of Conventional dosage forms:
 Periodic administration.
 Non-specific administration.
 High systemic concentrations can be
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The use of polymers in controlling the release of drugs has become important in the formulation of pharmaceuticals. Water soluble polymers such as polyethylene glycol and polyvinylpyrrolidone may be used to increase the dissolution rates of poorly soluble drugs. Hydrogels provide the basis for implantation, transdermal and oral controlled release systems. Hydroxypropyl methylcellulose (HPMC) is cellulose ether which may be used as the basis for hydrophilic matrices for controlled release oral
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