Exhibit 10.1

VOTING AGREEMENT

VOTING AGREEMENT, dated as of April 18, 2005 (this “ Agreement ”), among Orphan Medical, Inc., a Delaware corporation (the “ Company ”), Jazz Pharmaceuticals, Inc., a Delaware corporation (“ Buyer ”), Twist Merger Sub, Inc., a Delaware corporation (“ Sub ”), and certain stockholders of the Company whose names appear on Schedule I hereto (each a “ Stockholder ” and collectively, the “ Stockholders ”).

W I T N E S S E T H:

WHEREAS, contemporaneously with the execution and delivery of this Agreement, the Company, Buyer and Sub are entering into a Merger Agreement (as such agreement may hereafter be amended from time to time, the “ Merger Agreement ”), which provides for, upon the terms and subject to the conditions set forth therein, the merger of a Sub with and into the Company (as set forth in the Merger Agreement) in exchange for a cash payment for all of the issued and outstanding shares of capital stock of the Company (the “ Merger ”);

WHEREAS, as of the date hereof, each Stockholder beneficially owns (as such term is defined pursuant to Rule 13d-3(a) promulgated under the Exchange Act) the number of shares and/or warrants to purchase the number of shares of Senior Convertible Preferred Stock, $0.01 par value per share (the “ Senior Preferred Stock ”), Series B Convertible Preferred Stock, $0.01 par value per share (the “ Series B Preferred Stock ”), Series C Convertible Preferred Stock, $0.01 par value per share (the “ Series C Preferred Stock ”) and Series D Non-Voting Convertible Preferred Stock, $0.01 par value per share (the “ Series D Preferred Stock ,” together with the Senior Preferred Stock, the Series B Preferred Stock and the Series C Preferred Stock, the “ Company Preferred Stock ”), and Common Stock, $0.01 par value per share (“ Company Common Stock ” and, together with Company Preferred Stock, the “ Company Capital Shares ”), of the Company set forth opposite such Stockholder’s name on Schedule I hereto (all such shares so owned and for which beneficial ownership may hereafter be acquired by such Stockholder prior to the termination of this Agreement, whether upon the exercise of options, conversion of convertible securities, exercise of warrants or by means of purchase, dividend, distribution or otherwise, being referred to herein as such Stockholder’s Subject Shares);

WHEREAS, approval of the Merger Agreement by (i) the holders of a majority of the issued and outstanding shares of Company Common Stock voting together with the holders of the Senior Preferred Stock voting on an as converted basis and (ii) the holders of a majority of the issued and outstanding shares of Senior Preferred Stock, voting as a separate class, is required in order to consummate the transactions contemplated by the Merger Agreement;

WHEREAS, as a condition to the willingness of Buyer to enter into the Merger Agreement, Buyer has requested that each Stockholder enter into this Agreement; and

WHEREAS, in order to induce Buyer to enter into the Merger Agreement, each of the Stockholders is willing to enter into this Agreement.

NOW, THEREFORE, in consideration of the foregoing and the mutual covenants and agreements herein contained, and intending to be legally bound hereby, Buyer, Sub, the Company and the Stockholders hereby agree as follows:

ARTICLE I.

DEFINITIONS

Certain capitalized terms used and not otherwise defined herein have the meanings ascribed to them in the Merger Agreement.  Unless the context otherwise requires, such terms shall include the singular and plural and the conjunctive and disjunctive forms of the terms defined.

ARTICLE II.

VOTING OF SHARES

SECTION 2.1.                        Agreement to Vote .  From the date hereof until the termination of this Agreement pursuant to Section 4.1 hereof (the “ Term ”), at every time as the Company convenes a meeting of or otherwise seeks a vote of, the Company’s stockholders for the purpose of approving the Merger, each of the Stockholders hereby agrees to vote, or cause to be voted, to the extent not voted by Buyer as appointed by the Proxy, all of Stockholder’s Subject Shares:

(a)  in favor of the approval and adoption of the Merger Agreement and the approval of the Merger and the transactions contemplated by the Merger Agreement;

(b)  against approval of any proposal made in opposition to, or in competition with, the Merger and the transactions contemplated by the Merger Agreement; and

(c)  against any actions (other than those actions that relate to the Merger and the transactions contemplated by the Merger Agreement) that are intended to, or could be reasonably expected to, impair the ability of the Company to consummate the Merger or otherwise impede, interfere with, delay, postpone, discourage or adversely affect the consummation of the Merger in accordance with the terms of the Merger Agreement.

Each Stockholder further agrees not to enter into any agreement or understanding with any person to vote or give instructions in any manner inconsistent with or violative of the terms of this Section 2.1.

SECTION 2.2.                        Proxy; Reliance .  Each Stockholder hereby constitutes and appoints Buyer, acting through each of Matt Fust and Carol Gamble, each with the power to act alone and with full power of substitution and resubstitution, at any time during the Term, as its true and lawful attorneys-in-fact and proxies (its “ Proxy ”), for and in its name, place and stead, to vote such Stockholder’s Subject Shares as its Proxy, at every annual, special, adjourned or postponed meeting of the stockholders of the Company called for purposes of considering whether to approve the Merger Agreement or any of the other transactions or matters contemplated by, or directly or indirectly affecting, the Merger Agreement or to execute a

2

written consent of stockholders in lieu of any such meeting.  Each Stockholder understands and acknowledges that Buyer and Sub have entered into the Purchase Agreement in reliance upon each Stockholder’s execution and delivery of this Agreement.  The parties agree that by reason of the Merger Agreement, the Proxy is a proxy coupled with an interest.  At Buyer’s request, each Stockholder will perform such further acts and execute such further documents as may be required to vest in Buyer or its Representatives the sole power to vote Stockholder’s Subject Shares with respect to the matters set forth in Section 2.1 during the Term in accordance with the terms of this Agreement.

THE FOREGOING PROXY AND POWER OF ATTORNEY ARE IRREVOCABLE AND COUPLED WITH AN INTEREST THROUGHOUT THE TERM.

SECTION 2.3.                        Limitation .  Each Stockholder shall retain at all times the right to vote such Stockholder’s Subject Shares in such Stockholder’s sole discretion and without any other limitation on those matters other than those set forth in Section 2.1 that are at any time or from time to time presented for consideration by the Company’s stockholders generally.

SECTION 2.4.                        Capacity .  The parties hereby agree that the Stockholders are executing this Agreement solely in their capacity as stockholders of the Company.  Nothing contained in this Agreement shall limit or otherwise affect, in any manner, the conduct or exercise of the Stockholders’ fiduciary duties as officers or directors of the Company, where applicable.

SECTION 2.5.                        Transfer of Subject Shares .  Except as otherwise contemplated by the Merger Agreement, from and after the date of this Agreement until the termination of this Agreement, each Stockholder agrees that it will be the beneficial owner of all of such Stockholder’s Subject Shares and will hold such Subject Share