Med-Tech Innovation Drug delivery
Future Controlled-Release DRUG DELIVERY
Iain Simpson of Cambridge Consultants charts recent advances in controlled-release drug delivery and explores some of the opportunities for closed-loop delivery systems.
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www.med-techinnovation.com
ffective treatment of many diseases requires the concentration of a drug to be maintained above a minimum effective threshold yet below a maximum safe limit (that is, within the therapeutic window). Following administration, the drug concentration will initially rise as the drug is taken up systemically and then fall as the drug is metabolised (Figure 1). If the circulatory half-life of the drug is short, maintaining the drug concentration within the therapeutic window becomes challenging without frequent administration of the drug, which could then reduce patient adherence to the treatment. Formulation technologies such as PEGylation, in which the addition of polyethyleneglcol to the drug molecule “masks” it from the host immune system and hence can increase the circulatory half-life of some drugs, have been developed to address this issue. However these technologies are not appropriate for all drugs and can lead to complications such as immunogenicity. Another approach is to automate the drug administration to allow for continuous delivery using
device technology. One such device approach is to use an osmetic pump that can be swallowed as a pill or implanted. These systems use a chemical to generate pressure by osmosis to expel the drug from the device. This technology has come to market to deliver a number of drugs, including Ditropan XL for incontinence and Glucotrol XL for diabetes. However, the technology has limitations around dose size and can be affected by food and gastric transit time. An alternative approach is to use an external pump or to deliver a drug subcutaneously; a technology that is already commonplace in the delivery of insulin for diabetes, but is now being developed for other indications. For example, Steadymed (
www.steadymed.com) is developing a small wearable patch pump to deliver a drug to treat pulmonary arterial hypertension, and in 2013 Insulet (
https://www.myomnipod.com) announced an agreement with Amgen (
www.amgen.com) to use its OmniPod pump, originally developed to deliver insulin, to deliver unspecifi ed Amgen drugs. AbbVie (
www.abbvie.co.uk) is
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