Answer
Mr. Proux's increased susceptibility to cold is mostly likely due to the fact that one of the glucocorticoid effects of prednisone has been the suppression of his immune system. This has made his body less able to ward off the attacks of cold viruses.
The development of edema is not easy to explain because the dose of prednisone is not given. The side effect of edema is more closely associated with mineralocorticoids like aldosterone. However, prednisone does have weak mineralocorticoid effects --less than one thousandth as strong as those of aldosterone. Edema is a side effect of mineralocorticoid treatment because
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Glucocorticoids like prednisone have powerful anti-inflammatory effects. They are therefore useful in the treatment of rheumatoid arthritis-- but not recommended for treatment of osteoarthritis. In Mr. Proulx' case neither the dose of prednisone nor the kind of arthritis is known (given). What is known with certainty is that prednisone is a powerful suppressant of the immune system--much more powerful than cortisol. After treatment, Mr Proulx' was coming down with frequent colds because prednisone had depressed his immune defence against the cold virus.
Edema ia a side effect of mineralocorticoid therapy. Given the known very weak mineralocorticoid
effect of prednisone (compaired with aldosterone), one suspects that the duration of treatment was too long. Corticoids are usually given for brief periods of from five days to two weeks. Six weeks and eight weeks are long periods to be on oral steroid therapy. When such long periods of steroid therapy are employed, the steroid should be withdrawn slowly to provide time for the anterior pituitary and adrenal cortex to recover and take over the production of the steroids vital for health. In any case , mineralocorticoid therapy is known to produce the following side effects: increase in blood pressure (hypertension), muscle weakness, fatigue, depression , insomnia, and decrease in libido. Treatment with mineralocorticoids also affects the balance of electrolytes: sodium, and calcium ions are retained and excretion of potassium ions is promoted. As a consequence, the body retains water, and edema develops.