A trigger point injection can contain a variety of medications. There are two main types of medications that can be used — anesthetics and corticosteroids — and several additional types of each.

Anesthetic injections

Most trigger point injections contain a fast-acting numbing agent known as an anesthetic. Lidocaine is perhaps the most common, although procaine, prilocaine and tropisteron are also frequently used. These medications work by temporarily numbing and relaxing the affected muscles.

Corticosteroid injections

Corticosteroids, such as cortisone, can also be used in trigger point injections. These medications are powerful anti-inflammatory substances that can:

• Limit the extent to which the blood vessels in a muscle can dilate
• Prevent immune cells from accumulating around injured tissue
• Prevent the body from releasing enzymes that attack damaged muscles
• Reduce the body’s production of prostaglandins, which are hormones that intentionally cause inflammation as part of the healing process

Corticosteroids usually take longer to work than anesthetics, but the results of corticosteroid treatment can be longer lasting.

Combination injections

Sometimes, a trigger point injection can contain both an anesthetic and corticosteroid to provide both short-term and long-term pain relief. While a single trigger point injection is often sufficient, some people require multiple injections to fully release a severe trigger point. Some people are also prone to developing repeated trigger points and use injections as a recurring form of treatment.

Injections that only contain anesthetic medication can be given on a more frequent basis than those that contain corticosteroids. Some people receive anesthetic injections as often as once per month. Corticosteroid injections, on the other hand, are usually limited to three or four per year. Although trigger point injections are associated with very few side effects, some studies suggest that repeated cortisone shots can potentially cause long-term damage to muscles and joints. This has led to the development of conservative usage guidelines.