This is an antibiotic that has figured prominently in recent news items about cases of Duchenne due to premature "stop codons." In these cases the complete gene for dystrophin is never "decoded" or translated so that this critical muscle protein is not made, or at least not made in full form. Research on mdx mice that simulate human Duchenne has shown that when gentamycin is administered, the premature stop codon is somehow ignored so that the entire gene transcript can be "read" and dystrophin can be produced. A preliminary trial on Duchenne young men is underway, and hopes are high that this will work in humans as well as it did in the model mice. Unfortunately, this treatment would only work for those instances (about 10% of all Duchenne cases) in which the gene defect is a premature stop codon.
Transdermal patches (adhesive patches placed on the skin) may also be used to deliver a steady dose through the skin and into the bloodstream. Testosterone-containing creams and gels that are applied daily to the skin are also available, but absorption is inefficient (roughly 10%, varying between individuals) and these treatments tend to be more expensive. Individuals who are especially physically active and/or bathe often may not be good candidates, since the medication can be washed off and may take up to six hours to be fully absorbed. There is also the risk that an intimate partner or child may come in contact with the application site and inadvertently dose himself or herself; children and women are highly sensitive to testosterone and can suffer unintended masculinization and health effects, even from small doses. Injection is the most common method used by individuals administering AAS for non-medical purposes. 
Help I have a friend who is a gym goer Im not sure of his quantity or how long he has been taking steroids, but stopped recently because he had really bad neck pain. No dr or scan, ultrasound etc showed anything. Put on huge pain killer amounts didnt help alot but felt after about six weeks some relief. Until today when he thinks a prior knee issue has flared up. If this a result of steroid abuse how long before it heals? Im pretty sure he wont touch them again. He can handle all over aches and pains but these last two injuries have had him off work.