New therapeutic agents are constantly being developed in order to treat new and current disease states. Many of these new compounds display a narrower therapeutic range, where the difference in concentrations between effective treatment and toxicity becomes smaller1. As a result, controlling drug release to stay in these tightening ranges becomes more and more important to effectively treat patients. The proper management of some diseases has been shown to be dependent upon achieving consistent pharmacokinetic profiles2, which is reliant on the timing of dosages, paired with the total compliance of the patient. For many specific patient populations compliance with daily oral dosing presents inherent complications; e.g with schizophrenic and depressive patients. However, patients receiving continuous (ie, extended release) therapies have been shown to have lower rates of relapse, because of the constant dosing of medication3,4. Increasing the treatment length of a dose given by injection5 and finding preferential ways to deliver extended-release therapies are the basis for continued research in the formulation of extended or sustained-release injection products.;In many cases, trying to avoid a parenteral (injectable) route of administration through oral dosing is not feasible or even desirable5. Therefore, the development of many sustained-release drug products results in injection-based products. Extending the release of a drug may be achieved through the manipulation of physiochemical properties, the use of formulation technologies such as microspheres and nanospheres6, and balancing the in vivo properties of the compound (such as half-life)7. This thesis will cover current options for developing extended-release pharmaceutical parenteral (injection) delivery systems including prodrugs, microspheres, traditional depots, and injectable implants that are currently approved or inprocess of approval by the United States Food and Drug Adminitration or approved in Canada.
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