HEROIN OVERDOSE RISK RISES AFTER ABSTINENCE

NEW YORK, Jun 26 (Reuters) -- Heroin users appear to be more susceptible to
overdose after periods of abstinence, according to a study in the June 27th
issue of The Lancet.

The findings come from analysis of drug levels in hair samples taken from
people who died of heroin overdose. "Drugs can be detected in hair tissue
weeks or months after intake," write the researchers.

These findings suggest that heroin addicts who relapse after abstaining
from the drug -- for instance, while in jail or treatment programs -- run a
higher risk of overdosing, note the authors, a team of researchers led by
Dr. Franco Tagliaro of the University of Verona in Italy.

The findings also suggest that "weekend" and occasional users run a higher
than average risk of overdosing on heroin, Tagliaro and colleagues warn.

Tagliaro's team tested the morphine content of hair samples from 37 heroin
addicts who died after overdosing on the drug. Morphine, the main active
metabolite of heroin, is taken up into hair, among other ways, via
surrounding blood vessels. Hair grows at a rate of about 1 centimeter
(almost half an inch) per month, so morphine deposits in hair can serve as
a record of drug use over time.

Tagliaro and colleagues compared the morphine content of hair from the
addicts who overdosed, with the morphine content of hair from 37 active
heroin addicts, 37 former users who had been abstinent for several months,
and 20 people who did not use the drug or other opiates.

The researchers found that the morphine content of hair from the addicts
who overdosed was similar to that of samples from the abstinent former
addicts. They found an average 1.15 nanograms (ng) of morphine per
milligram (mg) of hair in samples from the addicts who overdosed, compared
with 6.07 ng/mg in samples from active addicts, and 0.74 ng/mg in samples
from abstaining former addicts. Morphine levels in samples from people who
did not use opiates were below detectable limits, the researchers report.

The similarity between the morphine content of samples from the addicts who
overdosed and that of samples from abstaining former addicts, suggests
"that most individuals who died from heroin overdose had virtually
abstained from heroin during the 4 months preceding death," the authors write.

"Thus, the results of this hair analysis support a theory of high
susceptibility to opioid overdose after periods of intentional or
unintentional abstinence," they conclude. "This theory has been used to
explain the high number of deaths among addicts recently released from jail
or on completion of a detoxification programme."

"The results of our study should indicate to the medical staff of
detoxification programmes that there are risks inherent in relapse to
heroin intake following abstinence from the drug," they add. "In
particular, we point out the potential risk of 'opioid free' detoxification
programmes."

This study appears to be the first to use hair analysis to determine the
drug use histories of people who have died from heroin overdose, the
authors write. It is difficult to determine heroin use over time using
blood tests, for example, because heroin usually disappears from the blood
very quickly.

Exactly why heroin addicts appear more susceptible to overdose after
abstinence is unclear, Tagliaro and colleagues note. It may be that
abstinence, or occasional use, leads to a lower heroin tolerance, and
consequently, to "a corresponding decrease in the size of a fatal dose."
SOURCE: The Lancet 1998;351:1923-1925.

Copyright 1998 Reuters Limited.

Checked-by: Richard Lake