I don't know who originally wrote it, so instead of making a link, I'll just reproduce the text here. If you happen to know, tell me so I can give proper credit.
1. I will understand the effects of all recreational drugs I take prior to ingestion, to the best of my ability. I shall research all relevant neurochemical, psychological, physiological, and spiritual effects, the legal issues surrounding the drug and its use, along with other relevant information.
2. When taking a drug I am inexperienced with, I shall begin with a reasonably low dose suggested to be psychoactive by the aforementioned research before progressing to higher dosages. I will measure the drug carefully, with an accurate scale, when possible and applicable.
3. If it is possible that the drug may contain harmful adulterants or in fact be a different drug altogether, I shall have the drug chemically analyzed for purity and content. If this is not possible, I will use caution and/or follow the appropriate course of action.
4. I will learn the overdose limits for my own body weight and adjust them for any possible synergistic effects due to diet, prescription or other drugs. I will also adjust for dangerous side effects and my own health condition. I will also learn of any possible drug interactions and make sure I am not at risk.
5. While under the effects of a drug, I shall not take physical risks such as driving, climbing, swimming, or any other physical activity in which my actions may cause harm to myself or others.
6. When first using a drug I am inexperienced with, I shall take it in the company of an experienced user, also known as a sitter. The sitter will remain sober during this experience, and will also have fully researched the drug. If this is not possible I will make sure there is a responsible way/backup plan to deal with any haphazards which may occur during my experience.
7. I shall not attempt to sway, force, trick, or otherwise coerce another person or animal to take any drug; rather, I shall discuss previous drug experiences and research frankly and honestly, allowing all people to make their own personal decisions about drug use.
8. I shall defend the rights of others to make educated, responsible decisions about drug use. I shall not support any person or movement that attempts to remove or abridge said rights.
9. I shall not allow my drug use to overshadow or disrupt the other important aspects of my life, including social interaction, employment or even other personal pursuits.
10. I will also take responsibility for the drug use of friends and relatives, if their drug use becomes dangerous to their health or personal relationships.
11. I will take drugs only in my free time, when I am not answerable to an employer or responsible for another person's health and well-being.
12. As a drug consumer, I will embrace responsible drug production and distribution methods, such as growing or pharming your own, and shun suppliers who use violence when not necessary for their self-defense.
I swear this with the hope of creating a society in which safe, responsible drug use is a personal decision, not a criminal offense.