Certain drugs such as troleandomycin (TAO), erythromycin ( Ery-Tab , EryPed 200), and clarithromycin ( Biaxin ) and ketoconazole ( Nizoral ) can reduce the ability of the liver to metabolize (breakdown) corticosteroids and this may lead to an increase in the levels and side effects of corticosteroids in the body. On the other hand, phenobarbital, ephedrine , phenytoin ( Dilantin ), and rifampin ( Rifadin , Rimactane ) may reduce the blood levels of corticosteroids by increasing the breakdown of corticosteroids by the liver. This may necessitate an increase of corticosteroid dose when they are used in combination with these drugs.
Corticosteroids have been used as drug treatment for some time. Lewis Sarett of Merck & Co. was the first to synthesize cortisone, using a complicated 36-step process that started with deoxycholic acid, which was extracted from ox bile .  The low efficiency of converting deoxycholic acid into cortisone led to a cost of US $200 per gram. Russell Marker , at Syntex , discovered a much cheaper and more convenient starting material, diosgenin from wild Mexican yams . His conversion of diosgenin into progesterone by a four-step process now known as Marker degradation was an important step in mass production of all steroidal hormones, including cortisone and chemicals used in hormonal contraception .  In 1952, . Peterson and . Murray of Upjohn developed a process that used Rhizopus mold to oxidize progesterone into a compound that was readily converted to cortisone.  The ability to cheaply synthesize large quantities of cortisone from the diosgenin in yams resulted in a rapid drop in price to US $6 per gram, falling to $ per gram by 1980. Percy Julian's research also aided progress in the field.  The exact nature of cortisone's anti-inflammatory action remained a mystery for years after, however, until the leukocyte adhesion cascade and the role of phospholipase A2 in the production of prostaglandins and leukotrienes was fully understood in the early 1980s.
Osteoporosis is particularly common in smokers, postmenopausal women, the elderly, underweight or immobile, and patients with diabetes or lung problems. Osteoporosis may result in fractures of the spine, ribs or hip joint with minimal trauma. These occur after the first year in 10–20% of patients treated with more than mg prednisone daily. It is estimated that up to 50% of patients on long-term prednisone will develop bone fractures. Vertebral fractures are more common in patients on steroids, even in those with normal bone density.