Method for applying a drug coating to a medical device

• US 7,282,213 B2
• Filed: 09/30/2002
• Issued: 10/16/2007
• Est. Priority Date: 09/30/2002
• Status: Expired due to Fees

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Chaffin, Kimberly A., Schroeder, Peter T.
• Primary Examiner(s): Hartley; Michael G.
• Assistant Examiner(s): YOUNG, MICAH PAUL
• Application Number:
  US10/260,659
• Publication Number:
  US 20040062852A1
• Time in Patent Office: 1,842 Days
• Field of Search: 424422-426, 607/115, 607/116, 607/120
• US Class Current: 424/422
• 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 method for applying a steroid coating to a medical device electrode, the method comprising the steps of:

preparing a saturated solution comprising a steroid dissolved in an organic solvent;

depositing the solution on a surface of the electrode driving off the organic solvent to form a coating having a crystalline structure on the electrode surface; and

inducing micro-crack healing of the coating by heating the coating formed after the organic solvent has been substantially driven off.

2. The method of claim 1, further comprising the step of preparing the surface of the electrode to promote adhesion of the steroid prior to the depositing step.

3. The method of claim 1, further comprising the step of mixing the steroid with the organic solvent.

4. The method of claim 3, wherein the mixture is a saturated solution.

5. The method of claim 1, wherein the solvent comprises acetone.

6. The method of claim 1, wherein the solvent comprises methanol.

7. The method of claim 1, wherein the solvent comprises chloroform.

8. The method of claim 1, wherein the steroid is sparingly soluble in water.

9. The method of claim 8, wherein the steroid comprises beclomethasone diproprionate anhydrous.

10. The method of claim 1, wherein the steroid comprises dexamethasone.

11. The method of claim 1, wherein the coating is heated to a transition point resulting in a solid-state phase change of the coating.

12. The method of claim 1, wherein the coating is heated by directing a stream of hot air over the coating.

13. The method of claim 1, wherein the coating is heated by applying radio-frequency energy to the coating.

14. The method of claim 1, wherein the coating is heated by applying microwave energy to the coating.

15. The method of claim 11, wherein the steroid comprises beclomethasone diproprionate anhydrous and the coating is heated to a temperature between approximately 144 degrees Celsius and approximately 146 degrees Celsius.

16. The method of claim 3, wherein the depositing step comprises dipping the electrode into the mixture.

17. The method of claim 3, wherein the depositing step comprises dispensing the mixture of the steroid and the organic from a syringe.

18. The method of claim 12, further comprising the step of mounting the electrode on a fixture prior to the healing step and the healing step further comprises controlling the heating time by a motorized platform to which the fixture, on which the electrode is mounted, is coupled.

19. The method of claim 1, further comprising the step of assembling the medical device electrode into a lead.

20. A medical device prepared by the method of claim 1, comprising an electrode including a coating of steroid conforming to a surface of the electrode, the coating having a crystalline structure without micro-cracks.

21. The medical device of claim 20, further comprising an elongate lead body and wherein the electrode is a tip electrode terminating a distal end of the lead body.

22. The medical device of claim 21, wherein the tip electrode has a helical form.

23. The medical device of claim 21, wherein the tip electrode has a generally hemispherical form.

24. The medical device of claim 20, wherein the steroid comprises beclomethasone diproprionate anhydrous.

25. The medical device of claim 20, wherein the steroid comprises dexamethasone.

26. A method for applying a steroid coating to a medical device electrode, the method comprising the steps of:

preparing a saturated solution comprising a steroid dissolved in an organic solvent;

depositing the solution on a surface of the electrode

driving off the organic solvent to form a coating having a crystalline structure on the electrode surface; and

inducing micro-crack healing of the coating by heating the coating formed after the organic solvent has been substantially driven off, wherein

heating occurs such that a solid-state phase change occurs but less than a degradation temperature of the steroid.

27. The method of claim 26, wherein heating occurs at about 145 degrees Celsius.