These injections typically contain a mixture of a synthetic cortisone and a local anesthetic such as lidocaine. Cortisone is a steroid normally produced by the body and is a powerful anti-inflammatory. These anti-inflammatory steroids are very different from the anabolic steroids that have been abused by some athletes for body-building and performance enhancement.
The local anesthetic dissolves the steroid and numbs up the area of the injection, diminishing discomfort during the procedure.
There are several available synthetic cortisones that all have similar mechanisms although they vary in strength and duration of action (short versus long-acting). No single preparation has been found to be superior to others so the choice of medication is left up to the individual provider.
The injection should take effect within a few days and the benefits can last for many weeks. The exact timing, however, varies from patient to patient. For some conditions, one injection can be sufficient to completely get rid of the inflammation and pain while for more severe cases, several injections may be required. Most patients respond well to injections although a small subset may not experience any relief of symptoms.
There is no set rule as to how many injections a person can get. Many providers use three injections as a rule of thumb although, in some cases, more frequent injections may be helpful. Your response to the first injection is very important in determining whether to proceed with re-injection: If the first injection doesn’t work or wears off quickly it may not be worthwhile repeating. Many providers limit the number of injections because repeated cortisone may cause damage to tendons and/or cartilage.
If an injection is done for a condition that is aggravated by use (e.g. tendinitis, arthritis), it is also important to learn how to properly use that body part to ensure recurrence does not happen. Oftentimes, cortisone will mask the pain, but the underlying cause of the pain is still there. If this is due to arthritis, it is important to practice joint protection so further injury to the joint is not done. If the cause of pain is due to repetitive stress, continuing to repeat the stress may lead to worsening pain once the injection wears off.
The most common side effect of a cortisone injection is known as a flare reaction. This is thought to happen when the steroid crystallizes after being injected, leading to pain lasting one or two days after the injection. This pain can be worse than the initial discomfort for which the injection was given. Cortisone flares resolve spontaneously over a few days and can be treated with ice, an anti-inflammatory medication such as Ibuprofen and rest of the affected body part.
Another common side effect, especially in patients with darker skin, involves skin discoloration at the injection site. The skin becomes locally lighter in color and sometimes thinner. Although this can improve, the whitening of the skin can sometimes be permanent.
One of the more serious complications from these injections is an infection, especially if the injection was given into a joint. Fortunately infections are rare and can usually be prevented by carefully cleaning the skin before performing the injection. Very rarely, some patients may experience allergic reactions to the steroid or local anesthetic in the injection.
Diabetics may often notice a transient increase in their blood glucose in the days following an injection. Cortisone injections are usually safe during the last trimester of pregnancy and while breast-feeding. However, checking with your obstetrician would be advised prior to proceeding.