Method for applying a drug coating to a medical device

• US 20040062852A1
• Filed: 09/30/2002
• Published: 04/01/2004
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: A. Chaffin, Kimberly, Schroeder, Peter T.
• Granted Patent: US 7,282,213 B2
• Time in Patent Office: Days
• US Class Current: 427/2.1
• CPC Class Codes: A61N 1/0568 with drug delivery
• CPC Class Codes: A61N 1/0575 with drug delivery

Abstract

A method for coating a medical device with a drug is provided. Energy, preferably thermal energy, is applied to a crystalline deposit of a drug on the surface of a medical device to increase the molecular mobility and form a conformable drug coating with a low density of micro-cracks and other mechanical defects that can degrade the coating toughness and effective adhesion to the device surface. In a preferred embodiment, solution evaporation methods are used to deposit a crystalline coating of an anti-inflammatory steroid on a medical electrode. Heat applied at a controlled temperature, for a predetermined amount of time, induces a solid-state phase change of the drug coating providing a smooth, uniform, well-attached, conformable coating to form a layer that will elute from the electrode over time when implanted in a patient'"'"'s body.

Claims

1. A system to deposit a drug onto a medical device surface to increase molecular mobility and prevent microcracks, the system comprising:

means for depositing the drug on the medical device surface;

means for heating the drug to increase molecular mobility and elimination of microcracks; and

means for cooling the drug to produce a conformed drug coating on the surface of the medical device.

2. The system of claim 1 wherein the device includes an electrode of a medical lead on which surface the drug is coated.

3. The system of claim 1 wherein said means for hearting includes means for inducing a solid-state phase change that results in the elimination of said microcracks.

4. The system of claim 3 wherein said means to induce a solid-state phase includes means for thermally reorganizing a crystalline structure of the drug to produce the conformable coating with a lower defect density.

5. A method for coating a surface of a medical device, the method comprising:

depositing the drug coating on the surface of the medical device;

applying energy to the drug coating to increase molecular mobility; and

cooling the coating to form a conformable coating without degradation of the drug.

6. The system of claim 5 wherein a thermally induced reorganization of the crystalline structure of the drug is implemented to produce the conformable coating.

7. The method according to claim 5 wherein the imparted energy includes one of heat, radio frequency energy and microwave energy.

8. The method of claim 5 wherein said energy is selected dependent upon the material from which the medical device is formed.

9. The method of claim 5 wherein the drug is one of a steroid solution, a drug suspension or a pure powder form.

10. The method according to claim 5 wherein depositing said drug includes heating to a temperature equal to or greater than the solid-state transition point but less than the degradation temperature.

11. The method according to claim 10 wherein said heating is implemented to increase molecular mobility that allows effective microcrack healing and defect reduction without drug degradation.

12. An apparatus for depositing a drug on a surface comprising:

means for dispensing a controlled amount of a drug solution on the surface;

means for evaporating the solvent to produce a dry crystalline coating;

means for heating the coating; and

means for setting the heating temperature in correlation with the thermal properties of the drug.

13. The apparatus of claim 12 wherein said means for controlling the heating temperature includes means for setting a range from a temperature that induces a solid-state phase change to a temperature less than the degradation point of the drug.