http://www.cancer.org/docroot/CDG/content/CDG_prednisone.html (exerpt -
read the rest)
Trade Name(s):
Apo-Prednisone, Orasone, Deltasone, Prednisone (there are other names
too)

Type of Drug:
Prednisone is a glucocorticoid steroid used to treat anorexia and
cachexia and some cancers. It is similar to a steroid hormone made by
the adrenal glands in the body.

 How Drug Works:
Prednisone decreases inflammation by preventing white blood cells from
completing an inflammatory reaction. This drug can cause lymphocytes, a
type of white blood cell, to break apart and die. Thus it is an
important drug used in combination with other chemotherapy agents to
treat many different cancers.

Precautions:
While you are being treated with prednisone, and after you stop
treatment, do not have any immunizations (vaccinations) without your
doctor’s okay. Try to avoid contact with people who have recently taken
the oral polio vaccine. Check with your doctor about this.

If you have a stomach ulcer, you may not be able to take this drug, or
may need extra medicines to protect your stomach. Check with your doctor
about this. When you take this drug, if you develop stomach pain or
vomit any blood, tell your doctor immediately.

This drug may suppress the immune system and increase your
susceptibility to infections. In addition, the drug may mask the signs
of infection such as fever.

The dose and number of days you should take the medicine will be
prescribed by your doctor and depends upon whether you are being treated
for anorexia or cancer.

If you take prednisone for a long time, do not stop the medicine
abruptly, as this can cause a decrease in the adrenalin your body makes
(adrenal insufficiency). Symptoms of this are nausea, loss of appetite,
tiredness, dizziness, difficulty breathing, joint pain, depression, low
blood sugar, and low blood pressure.

If you are a diabetic, this medicine will increase your blood sugar
levels and you may need to take extra diabetes medicine. Talk to your
doctor about this.

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Tell all the doctors, dentists, and pharmacists you visit that you are
taking this drug.
Most of the following side effects probably will not occur.
Your doctor or nurse will want to discuss specific care instructions
with you.
They can help you understand these side effects and help you deal with
them.

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Side Effects:

 More common side effects:

Delayed wound healing
Mood changes
Depression
Increased blood sugar
Increased appetite with weight gain
Bruising of the skin
Sleep disturbance
Increased risk of infection
Sodium and fluid retention with swelling in ankles, increased blood
pressure, and congestive heart failure

 Less common side effects:
Decrease in potassium blood level (symptoms are loss of appetite, muscle
twitching, increased thirst, and increased urination)
Weakness
Fracture of weak bones
Fungal infections (white patches in the mouth, vagina)
Sweating
Diarrhea
Nausea
Headache
Increased heart rate
Loss of calcium from bones