Almost all analgesic (pain-relieving) medication has limited efficacy for some types of pain. Medical marihuana is particularly useful because it has a broad spectrum of efficacy and a unique set of side effects.
Also, many effects that were once thought of as merely side effects are now considered beneficial for pain management. Marihuana is particularly useful for patients who have developed tolerance to opiates. Opiates, such as codeine and morphine, are commonly used to treat acute pain, but they are not consistently effective when treating chronic pain. Most opiates can also induce nausea. Marihuana is not only beneficial in treating nausea and pain, but there has also been recent research pointing to how marihuana cannabinoids act on pathways in the brain that overlap with those activated by opiates, but through pharmacologically distinct mechanisms (source: Marihuana and Medicine: Assessing the Science Base; Institute of Medicine, 1999. page 140).
Cannabis has been shown to have powerful immune-modulation and anti-inflammatory properties, indicating it may treat chronic inflammatory diseases directly. In fact, one of the earliest records of medical use of cannabis, a Chinese text dating from 2000 BC, notes that cannabis “undoes rheumatism,” suggesting its anti-inflammatory effects were known even then.
There are also many patients who have found drastic and significant pain relief using cannabis specifically for nerve pain. More than 100 types of peripheral neuropathy have been identified, each with its own set of symptoms, causes, and treatment.
In the National Institute of Health (NIH) Report on Medical Marihuana, it was reported that their only scientific finding (excluding anecdotal reports) was that marihuana was most effective for nerve pain. Around every nerve ending are a number of receptors of one kind or another. At every nerve ending in the human body there are fewer opiate receptors than cannabinoid receptors, which means that cannabis is far more effective for stopping nerve pain than opiate drugs, (which do not work for nerve pain very well at all).