Naltrexone is a drug used in the treatment of opiate addiction. It reduces the craving for opiates by blocking opiate receptors throughout the body. Naltrexone also affects levels of two endorphins, or hormones, which play a key role in the regulation of the immune system and in communication between the brain and the immune system. These hormones are called beta endorphin and metenkephalin, and it has been reported that beta endorphin levels in people with AIDS are abnormally low.

It has been suggested that boosting the production of beta endorphin can improve the health of people infected with HIV. An increase in production of beta endorphin may reduce the levels of interferon alfa, which is believed by some researchers to be harmful if it is present at high levels during HIV infection.

Only one formal study of naltrexone has been conducted, back in the mid-1980s, and the results were not clear-cut. They could simply be the result of chance. The study showed that after eighteen months, individuals on naltrexone had stable CD4 counts, whilst those who had not received naltrexone had experienced declining CD4 counts over the same period. However, naltrexone is still used by the doctors who conducted the original trial, and they claim that many of their patients continue to derive benefit after long periods of naltrexone treatment.

Naltrexone must be used at a much lower dose than that prescribed as an opiate substitute. The suggested dose in HIV infection is 2.75 or 3 mg per day, once daily at night. Naltrexone should not be used during pregnancy or breast feeding, and by individuals with liver problems. No significant side-effects have been reported in association with the lower dose used in HIV infection.