|
Mr. Chairman, and Members of the Subcommittee, I
am pleased to be here to present what science has taught us about psychoactive
prescription drugs and their potential for abuse. This discussion is
particularly timely given that the National Institute on Drug Abuse (NIDA) has
recently launched a major initiative on prescription drug abuse and misuse. NIDA’s
renewed efforts to encourage more research into this area and to educate the
public about the consequences of abusing prescription drugs is a preemptive
strike on our part to curtail what our surveillance systems suggest is a growing
problem in this country.
At the outset, I would like to emphasize that
many substances can be two things at once. They can be very effective
medications when used properly; and highly addictive, dangerous, substances when
misused. When used for legitimate medical purposes, controlled substances such
as morphine and diazepam (Valium®), improve the quality of life for millions of
Americans with debilitating diseases and conditions. It is only when these
medications are used improperly that they begin to pose a serious public health
threat. It is the increasing use of these medications for purposes other than
how they were intended that is of growing concern to us.
Several indicators suggest that prescription drug
misuse and abuse are increasing in the U.S. population. We know that in 1999
more than 9 million Americans aged 12-and-older reported that they used
prescription drugs at least once in the past year for non-medical reasons. One
quarter or more of those 9 million people misused prescription drugs for the
first time in the year prior to the survey. And 4 million reported that they
used prescribed medications for non-medical reasons in the past month. These
data come from the National Household Survey on Drug Abuse, supported by the
Substance Abuse Mental Health Services Administration.
NIDA’s own Community Epidemiology Work Group, a
network of epidemiologists and researchers from 21 major U.S. metropolitan areas
who monitor and report on community-level trends in drug use and abuse, are also
seeing increases in abused prescription drugs. The latest CEWG report, for
example, reports that the opioid hydrocodone (e.g. Lorcet, Lortab, Vicodin)
appears to be one of the mostly widely abused prescribed medications. The number
of emergency room mentions of hydrocodone has grown by 139 percent, or from
6,115 mentions in 1993 to 14,639 in 1999. Other prescribed drugs that are
emerging on the scene and are causing increases in emergency room visits,
according to CEWG, are oxycodone and clonazepam.
Prescription drug abuse is not a new problem. The
significant increase in the numbers of people misusing these prescription drugs
is what is new. From 1990 to 1998, for example, the number of individuals
initiating misuse or abuse of pain relievers increased by 181%, new initiates to
stimulants have increased by 165%; tranquilizers by 132%; and initiates into
sedative use have increased by 90%. The most dramatic increases are found in
12-17 year-olds and 18 to 25 year-olds. Females in this younger age bracket
appear to be particularly vulnerable to prescription drug abuse.
Determining one’s vulnerability to addiction is
an important part of NIDA’s research portfolio. The fact that we do not fully
understand what makes some individuals more vulnerable to addiction than others
makes our concern about prescription drugs even more compelling. There are major
differences among individuals in sensitivity to various drugs of abuse. Using
advanced technologies, we recently found that differences in brain chemistry may
be one of the factors that predisposes people to respond differently to abusable
drugs. Other determinants of drug use preferences and patterns include genetic
and environmental factors, a possible underlying medical illness, as well as
factors such as the availability of drugs.
What is significant about the brain chemistry
finding that I just mentioned is that all abusable drugs -- from alcohol and
nicotine, to cocaine, methamphetamine, and morphine – share some common
mechanisms of action. They all activate the neurotransmitter dopamine, which is
part of the reward pathway or pleasure center for the body. It is this
pleasurable effect that is likely the reason that 26.2 million Americans used an
abusable drug in the past year in 1999.
Although dopamine is a common factor among all
drugs of abuse, each class of drug acts at different sites in the brain to
produce its intended effect. For example opiates, such as morphine, codeine, and
oxycocodone, work predominantly at the mu opioid receptors found in the brain
and spinal cord, to block the transmission of pain messages to the brain.
Another commonly abused class of drugs is the
Central Nervous System (CNS) depressants. CNS depressants modulate actions of
gamma-aminobutyric acid (GABA) to slow down normal brain function. This
resulting calming effect is what makes CNS depressants so useful in the
treatment of anxiety and sleep disorders. Barbiturates such as mephobarbital and
pentobarbital; and benzodiazepines such as diazepam and alprazolam, are two
categories of CNS depressant medications that are commonly prescribed for
anxiety and sleep disorders.
The final class of commonly abused prescription
drugs that I will briefly mention today is stimulants. As the name suggests,
stimulants are a class of drug that enhance brain activity. They cause an
increase in alertness, attention, and energy by displacing two of the brain’s
key neurotransmitters, norepinephrine and dopamine, which in turn increases
blood pressure, heart rate, respiration, and blood glucose. Stimulants such as
dextroamphetamine, methylphenidate, and sibutramine are generally prescribed for
narcolepsy, attention-deficit hyperactivity disorder, obesity, as well as
depression, and asthma.
When taken properly all of these prescription
drugs that I have just mentioned can be extremely helpful in relieving a wide
variety of medical problems. It is when they are used non-medically, that
prescription drugs can be dangerous, addicting and even deadly.
Research has not yet completely revealed all the
reasons why people would abuse a prescribed medication. Some may just
intentionally abuse these drugs to receive the pleasurable effects, in the same
way that people abuse and become addicted to heroin or crack cocaine. Others
seem to begin to use them appropriately as prescribed, but then over time they
slowly begin to deviate from the prescription regimen and may become addicted
without ever intentionally setting out to abuse the drug in the first place. It
is important to note that physical dependence does not equal addiction. Physical
dependence can be relatively easily managed, whereas addiction -- the compulsion
to use drugs -- is a chronic reoccurring illness that requires long-term
treatment.
As I mentioned earlier, the same substance can be
both a very effective medicine and a dangerous addictive drug. Morphine, is the
perfect example. Morphine is a powerfully addictive drug. However, when it is
used to treat pain it is an extremely beneficial medicine. The medical use of
prescribed opiates effectively relieves both chronic and acute pain, and allows
millions of individuals to function normally. Addiction under these
circumstances is very rare. In fact, the combined data from three clinical
studies found that in patients with no prior history of abuse, opiates used for
the treatment of pain was associated with only 7 cases of addiction in a sample
of about 25,000 people.
Another example of how beneficial medications can
be when used as prescribed can be seen with the stimulant methylphenidate, known
commonly as Ritalin®. Data accumulated over 30 years shows that methylphenidate
is a safe medication when appropriately used for the treatment of
attention-deficit hyperactivity disorder (ADHD). ADHD affects about 3 to 5
percent of the general population and is now one of the most visible childhood
mental disorders. A number of studies indicate that ADHD youth that are
appropriately treated with stimulant medications have a reduction in the risk of
later substance abuse.
In conclusion, I would like to thank you for
allowing me to be here to have science be a part of your discussion on this
topic. NIDA is increasing its research efforts into this area and will be
pleased to keep you abreast of any new findings that emerge that may help guide
your policy decisions.
|
