Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Patent
1993-11-17
1997-01-14
Azpuru, Carlos
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
424424, 424426, 424501, 5147723, A61F 202, A61K 916, A61K 950
Patent
active
055936970
DESCRIPTION:
BRIEF SUMMARY
This invention relates to biocompatible or biodegradable implants, for veterinary or human applications, and especially to such implants which can be administered subcutaneously or intramuscularly.
The invention is particularly, but not exclusively, concerned with biocompatible or biodegradable implants for the administration of antigens to animals including man, which provide a pulsed release of antigen at a period of time after implantation, ie. in which release is delayed. The time delay can be controlled by varying the formulation of the implant. Although the invention is described by reference to vaccines comprising an antigen, optionally administered together with an adjuvant, the person skilled in the art will readily appreciate that the invention is equally applicable to the pulse release of any agent. Examples of such other agents include antibodies, hormones, growth promotants, antibiotics, nutrients, minerals, vitamins, and so on.
For the purposes of the present specification "biocompatible" is to be taken to mean that all components of the implant should be physiologically tolerable and should not cause an adverse local or systemic response when implanted. "Biodegradable" means that the components are degraded into harmless components which are either metabolized or excreted.
BACKGROUND AND PRIOR ART
It has long been appreciated that multiple injections of certain antigens are required to elicit an adequate immune response and production of antibodies [1]. A suitable and widely used method is the sub-dermal or subcutaneous injection of antigen together with one or more adjuvants in liquid formulations by needle. However, the necessity for such multiple injections has greatly increased the cost and inconvenience of immunization programes both in human and veterinary medicine. Furthermore, in third world countries, not only has the need for such multiple injections meant that many human patients receive an incomplete course of immunisation, but conditions are often such that liquid formulations for injections are subject to adverse storage conditions, or made up under non-sterile conditions.
In veterinary and human medicine there is therefore a need for dosage forms which after a single administration result in the release of antigen at different times [5,7]. The release may be continuous or occur as one or more pulses delayed for a period of time after administration. Such a delayed release implant has considerable potential in veterinary medicine as it allows two or more doses of antigen to be administered in a single handling of the animal, resulting in significant cost saving. The use of such a delivery system in human medicine in third world countries would also contribute significantly to savings in utilization of scarce medical resources, as co-administration of immediate and delayed release implants permits a second pulse of antigen to be released a set time period after implantation. This ensures that the booster dose of antigen is received, which in many vaccines is essential to achieve appropriate efficacy.
Small, usually cylindrically shaped implants, which are inserted into the subcutaneous tissue using a specially designed implanter, have been widely used as controlled release delivery systems in veterinary medicine (2,3). The polymers and excipients used in such devices must be biocompatible (2) and or biodegradable (2,16,17). Applications suggested for veterinary controlled release devices include disease prevention, growth promotion, vaccination, fertility control, and supplementation of nutritional agents (4,5). Recently, Caster, Luttinger and Gardner [4] have reviewed the use of controlled release parenteral systems for veterinary use and tabulate commercially available products and delivery systems under development. In humans, subcutaneous delivery systems based on Silicone tube implants have been used to deliver steroids and anti-inflammatory drugs (6). Modulated and triggered drug delivery systems which use pH sensitive polymers in subdermal devices are being developed (
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Controlled Drug Delivery, Fundamentals and Applications, Second Edition Robinson and Lee, Eds., Marcel Dekker, Inc. pp. 481-516.
Drug Delivery Devices, Fundamentals and Applications, Tyle, Ed., Marcel Dekker, Inc. pp. 33 and 591-600.
Biodegradable Polymers As Drug Delivery Systems, Ed. M. Chasin and R. Langer (Marcel Dekker), Chapter 1, pp. 5-8.
Agyilirah, G. A. and Banker, G. S., in Polymers For Controlled Drug Delivery, Tarcha, Ed., Chapter 3, "Polymers for Enteric Coating Applications", CRC pp. 40-41, CRC Press (1991).
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Chemical Technology Reivew, No. 177; "Sustained Release Medications"; edited by J. C. Johnson (New Jersey); issued 1980; see pp. 179-180.
Barr Ian G.
Thiel William J.
Azpuru Carlos
CSL Limited
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