Sunday, July 13, 2008
No Pill for Stimulant Addiction
Meth and cocaine continue to elude researchers.
Despite promising trials of several compounds, methamphetamine addiction remains largely impervious to anti-craving pills and other forms of drug treatment. According to a paper in the June issue of Addiction Science and Clinical Practice, "currently, no medications are approved by the FDA for the treatment of stimulant dependence. However, recent advances in understanding... have allowed researchers to identify several promising candidates."
The paper's author, Dr. Kyle Kampman of the University of Pennsylvania School of Medicine and Treatment Research Center, notes that "the demand for treatment for cocaine dependence remained roughly level from 1992 to 2005, while the demand for treatment for amphetamine dependence increased about eight-fold." (See chart above).
As I wrote earlier ("FDA Puts Coke/Meth Treatment on Fast Track"), the U.S. Food and Drug Administration (FDA) in January gave Fast Track designation to vigabatrin, sold as Sabril by Ovation Pharmaceuticals. Ovation is collaborating with the NIDA on Phase II studies to evaluate the safety of Sabril, with Phase III trials scheduled for the end of this year.
Vigabatrin, an anti-epilepsy drug called Gamma-vinyl-GABA, or GVG for short, showed early promise for use with cocaine addicts in a 60-day study and appears to increase GABA transmission. GABA has an inhibitory effect on dopamine and serotonin release.
Another entry in the vigabatrin sweepstakes, Catalyst Pharmaceuticals, is also testing its version of the drug, dubbed CPP-109, for the treatment of methamphetamine addiction in Phase II double-blind, placebo-controlled studies. Patrick J. McEnany, chief executive officer of Catalyst, commented, "We are excited to follow up on our cocaine trial with the initiation of our second, large-scale U.S. Phase II trial with CPP-109, this time as a potential treatment for methamphetamine addiction. As with cocaine, we believe that CPP-109 may offer the potential to provide patients suffering from methamphetamine addiction, as well as the physicians and clinicians that treat them, with a safe and effective pharmacotherapy option."
What, in essence, are such pills designed to accomplish? The primary avenue of research has centered upon medications that decrease the addict's experience of withdrawal and craving. According to Kampan, "several studies have demonstrated that patients who experience severe cocaine withdrawal symptoms... are twice as likely to drop out of treatment and less likely to attain abstinence in outpatient programs."
However, questions remain about the safety of vigabatrin. Although available abroad, it is not approved for use in the U.S., due to an association with serious visual effects after long-term use. The use of vigabatrin for stimulant addiction, if approved, might require associated eye examinations.
Buproprion, a drug that has shown some promise in the treatment of cocaine addiction, is also a candidate for meth addiction. The drug inhibits the reuptake of dopamine, thus allowing more dopamine to circulate in the brain. In addition, there are plans to test other drugs being investigated for cocaine craving, such as topiramate and modafinil.
According to the 2005 SAMHSA Survey on Drug Use and Health, an estimated 10.4 million people age 12 or older (4.3 percent of the population) have tried methamphetamine at some time in their lives. Approximately 1.3 million reported past-year methamphetamine use, and 512,000 reported current (past-month) use. Approximately 535,000 patients sought treatment for methamphetamine and other stimulant abuse in 2006.
Next post: Drugs for cocaine craving
Photo Credit: National Drug Intelligence Center