Oxsoralen (methoxsalen) is a repigmenting agent. It is similar in structure and action to Trisoralen (trioxsalen). Both of these drugs belong in a medicines known as psoralens, which are used along with ultra violet light exposure to treat certain disorders of the skin such as Vitiligo (where skin pigment is lost) and psoriasis (a skin condition characterized by red and scaly blotches). Although the exact underlying mechanism behind these agents is unknown, they ultimately work to produce the output of melanin in response to stimulation by sunlight (or artificial UV exposure) This enhances the rate of pigmentation, which in many cases will allow the lighter areas of the skin to become more evenly colored.
Bodybuilders are attracted to psoralens because they may be used to help them develop that deep tan that is so favored in the world of competition and modeling. A good tan helps bring out muscle separation and definition tremendously, to the point is just about considered a necessity. A natural tan looks much better especially when you are going to be seeing people face to face. This drives many fairer skinned people to look for drugs that can help them achieve a deep bronze look that is otherwise difficult or impossible to achieve on their own. In this regard, Oxsoralen certainly seems to deliver, at least for most people who have carefully and correctly used the drug.
It is important to remember that this drug offers you no protection from the sun. It is most certainly nothing like using suntan lotion. In fact, since it increases the skin's sensativity to sunlight, it can actually make one much more prone to skin damage. Medical professionals never prescribe it for the simple purpose of cosmetic enhancement of ones "tan" for this reason. If asked, your doctor will most likely point out that it has caused very serious sunburns when not properly used, even to the point of increasing a person's chance of suffering from skin cancer and cataracts. Like getting too much sunlight, it can also cause your skin to prematurely age. There are many serious concerns with the use of this drug, so do not let the fact that it is used for something as simple as tanning fool you into thinking its benign. It most certainly is not. I assure you, if you use it incorrectly, you may wind up wishing you never heard of Oxsoralen.
The actual dose used is usually tailored to one's bodyweight and individual sensitivity to the drug. For this reason most bodybuilders will start by taking a single capsule or tablet per day, and increase the drug slowly, over time, to a point no more than the recommended medical dose for their bodyweight. According to the accompanying paperwork, this would be a maximum of 40mg for one weighing 146-176 pounds, 50mg for a weight of 179-198lbs, and 60mg for people less than 255lbs. Exposure to sunlight or ultraviolet light also must take place a certain number of hours after you take the medicine, or it will not work. For patients taking the normal capsules of methoxsalen, this will be 2 to 4 hours after administration. For patients taking the Oxsoralin Ultra softgels (which are digested much more rapidly) they will need to wait only 1 1/2 to 2 hours. The amount of time one spends xposed to light will usually also be increased slowly, starting with very brief intervals as the user becomes accustomed to the drug. The sheer number of variables, with both natural and artificial sunlight (time of year, location, total UV exposure), makes it impossible to give exact recommendations as to how long, so it will be important to judge your own exposure time and doseage response very carefully.