Pharmacy researchers urge caution, restraint regarding anti-addiction pill
Researchers at The University of Texas at Austin College of Pharmacy today urged caution and restraint in the use of an anti-addiction pill that recently received national attention as an effective treatment for addiction.
Drs. Rueben Gonzales and Richard Morrisett, professors on the College of Pharmacy's pharmacology/toxicology faculty, said that while the use of the anti-opiate drug naltrexone appears promising, there is much yet to be learned about how the drug works in the body.
The researchers responded Thursday to the story "With anti-addiction pill, 'no urge, no craving' " that appeared Wednesday on a national news website. Both researchers are working under a grant from the National Institute on Alcohol Abuse and Alcoholism to determine how naltrexone appears to decrease cravings for alcohol. Gonzales is the principal investigator of the five-year NIAAA grant that also involves research from Morrisett's lab.
Morrisett explained that "Naltrexone is a classic opiate receptor antagonist which blocks the actions of the endogenous "feel good" opiate peptides known as the endorphins." These endogenous peptides are released in response to injury, painful stimuli, and physical stress and are mimicked by very powerful narcotic agents including morphine, oxycontin and heroin. Naltrexone was originally marketed several decades ago to prevent respiratory depression and death following overdose from such powerful and dangerous drugs.
In recent years, the brain circuits that alcohol is believed to affect most have been identified and the circumstances that underlie alcohol addiction have begun to be unraveled. One critical circuit in the brain, known as the pleasure pathway, is thought to be especially involved in addiction.
"These circuits control our most basic urges and desires as well as our behaviors in response to such needs," Morrisett said. "Obviously, addiction is a disease in which control of urges to seek alcohol or other drugs has been lost and the exact manner in which changes in these complex brain circuits result in neuropsychiatric diseases such as alcoholism remain to be identified."
One of the most important signals in these brain regions is carried by the well-known neurotransmitter, dopamine. Stimulant drugs such as cocaine and methamphetamine work by activating this dopamine signal. Pharmacologists have suspected that dopamine itself may actually be the "feel good" signal.
"Recent research indicates, however, that dopamine most likely carries the signal that tells us that something good is about to happen but that it is not the actual "feel good" signal itself," Gonzales continued.
The use of naltrexone in limiting craving for alcohol has been studied for several years, and as documented in the article this week, the drug is effective. However, the exact mechanisms by which naltrexone limits craving for alcohol are not known. While it is true that the only known action of naltrexone is to block the actions of endogenous opiate peptides, researchers do not understand how these peptides may be involved in alcoholism. This is the target of the ongoing research labs directed by Gonzales and Morrisett.