There is no ethical or legal difficulty with using experimental large doses in extreme circumstances if the proper procedure to obtain Human Research Ethics Committee permission has been obtained. There are dangers to patients in individual practitioners operating outside evidence-based medicine. In fact the doctors greatly increase their legal liabilities if they do so without appropriate medical and ethical review. Dying patients should not be considered fair game for unproven clinical experimentation outside of the accepted review processes.
Testosterone can be administered parenterally , but it has more irregular prolonged absorption time and greater activity in muscle in enanthate , undecanoate , or cypionate ester form. These derivatives are hydrolyzed to release free testosterone at the site of injection; absorption rate (and thus injection schedule) varies among different esters, but medical injections are normally done anywhere between semi-weekly to once every 12 weeks. A more frequent schedule may be desirable in order to maintain a more constant level of hormone in the system.  Injectable steroids are typically administered into the muscle, not into the vein, to avoid sudden changes in the amount of the drug in the bloodstream. In addition, because estered testosterone is dissolved in oil, intravenous injection has the potential to cause a dangerous embolism (clot) in the bloodstream.