I read the article on the politics of addiction ["Cover Story," Jan. 30] that was devoted primarily to the controversy surrounding the use or lack of use of methadone in San Diego.

Heroin and similar drugs, collectively called "opioids," are the second most extensively studied drugs after alcohol. Unlike alcohol or drugs like cocaine and methamphetamines, opioids selectively bind with specific neurons in the brain called the "opiate receptors" and cause both beneficial effects like pain relief and also addiction.

Thanks to this knowledge, we have three distinct medications to treat opioid addictions--more than any other addictive drug except alcohol. The first and the most extensively used medication, and also the most controversial, is methadone, which binds with the opiate receptors, causing complete activation, but not to the same extent as heroin, thus breaking the cycle of withdrawal and cravings. The second medication is buprenorphine, better known by the trade name Suboxone. Buprenorphine binds with the opiate receptors, causing only partial activation. The third is naltrexone, which binds with the opiate receptor and prevents any activation.

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