Implantable Naltrexone More Effective Than Oral Formulation in Heroin Addiction: Presented at ECNP

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Title: Implantable Naltrexone More Effective Than Oral Formulation in Heroin Addiction: Presented at ECNP
URL: http://www.pslgroup.com/dg/22A77E.htm
Doctor's Guide
September 2, 2008

By Judith Moser, MD

BARCELONA, Spain -- September 2, 2008 -- Treatment retention and relapse prevention in patients with heroin addiction can be achieved more efficiently by the use of a long-acting sustained-release naltrexone implant compared with the oral formulation, according to a study presented here at the 21st European College of Neuropsychopharmacology Congress (ECNP).

The opioid antagonist naltrexone is approved for the treatment of heroin addiction, but its use shows limitations in clinical practice.

"The major problem with the oral formulation is suboptimal compliance," said study presenter Evgeny M. Krupitsky, MD, PhD, DSci, Laboratory of Clinical Psychopharmacology of Addictive States, St. Petersburg State Pavlov Medical University, and Department of Addictive Disorders, Bekhterev Research Psychoneurological Institute, St. Petersburg, Russia.

Dr. Krupitsky indicated that long-acting, sustained-release formulations of naltrexone, which are either injectable or implantable, encourage improved compliance and increase the efficiency of heroin addiction treatment.

The implantable formulation was recently registered in Russia for prevention of relapse in heroin addiction. It must be surgically inserted into the anterior abdominal wall and is active for at least 2 months, Dr. Krupitsky explained.

To test the efficacy of the long-acting, surgically-implantable formulation of naltrexone, Dr. Krupitsky and colleagues enrolled 190 patients with heroin addiction who had recently completed detoxification at addiction treatment units in St. Petersburg.

Participants were randomised to the following 3 treatment regimens: a naltrexone implant 1,000 mg every other month plus oral placebo daily (NI + OP; 66 patients); a placebo implant every other month plus oral naltrexone 50 mg QD (PI + ON; 62 patients); a placebo implant and an oral placebo (PI + OP; 62 patients).

Patients participated in a 6-month treatment course administered under double-dummy/double-blind conditions and biweekly drug counselling sessions.

Urine drug testing and brief psychiatric evaluations (depression, anxiety, anhedonia, and heroin craving) were performed 2 times a week. More extensive evaluations were performed at 3 and 6 months. Oral medication compliance was evaluated using a urine riboflavin marker.

The analysis revealed a significantly greater retention rate in the NI + OP group compared with the other groups (P < .01). By the end of 6 months, 77.3% of patients in the NI + OP group had not relapsed compared with 36.4% in the PI + ON group and 18.8% in PI + OP group (P < .001).

The researchers found no difference among the treatment groups in the number of heroin-positive urine samples. This was also true in psychometric terms.

The number of adverse effects was limited, with no differences among the study arms.

"We demonstrated the clear advantage of the implantable naltrexone formulation over oral naltrexone and placebo," Dr. Krupitsky concluded. "This way of management contributes to increasing the efficacy of the abstinence-oriented treatment of heroin-dependent patients."

[Presentation title: Double-Blind, Placebo-Controlled Trial of Effectiveness of Implantable Naltrexone (Prodetoxone) for Treatment of Heroin Addiction (Interim Analysis). Abstract P6c001]

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