Encyclopedia of Health and Medicine

318 Substance Abuse
leading health problem in the United States. Secondary
to alcoholism is a high risk for LIVER disease.
Because it metabolizes alcohol, the liver is
the organ most vulnerable to alcohol’s toxic
effects. Long-term excessive alcohol consumption
also increases the risk for LIVER CANCER, STOMACH
CANCER, COLORECTAL CANCER, BREAST CANCER, CORO-
NARY ARTERY DISEASE (CAD), hypertension, and
NUTRITIONAL DEFICIENCY.
See also ALCOHOLIC HALLUCINOSIS; CELL STRUCTURE
AND FUNCTION; DELIRIUM TREMENS; HEPATOTOXINS;
ILLICIT DRUG ABUSE; PRESCRIPTION DRUG ABUSE; SUB-
STANCE ABUSE PREVENTION; SUBSTANCE ABUSE TREAT-
MENT.
alcohol interactions with medications The
numerous ways in which ALCOHOL intensifies or
inhibits the actions and side effects of prescription
and OVER-THE-COUNTER (OTC) DRUGS. Alcohol also
interacts with illicit drugs though often unpredictably
because of their uncertain composition.
As well, some drugs interact with alcohol in ways
that alter alcohol’s METABOLISM and actions in the
body. Alcohol-medication interactions are of
increasing concern as more than 70 percent of
Americans take regular medications and at least
10 percent of them drink alcohol daily.
Liver Enzymes and Drug Metabolism
The LIVER produces CYTOCHROME P450 (CYP450)
ENZYMES that metabolize (break down into their
chemical components) most drugs that enter the
body. The enzymes act at predictable rates for specific
substances, one of the key factors in establishing
appropriate DRUG dosages. Alcohol–medication
interactions occur in two general ways: through
competition for the enzymes that metabolize them
(short-term or acute alcohol consumption) and
through changes in the way the liver produces
these enzymes (long-term or chronic alcohol consumption).
Because the primary interaction
between alcohol and medications occurs at this
enzyme level, alcohol affects in some way the
actions of nearly all medications.
In the short term, acute alcohol consumption
(drinking alcoholic beverages) engages the
CYP450 enzymes available in the liver. Consequently
fewer enzymes are then available to
metabolize other substances such as medications.
This reduced enzyme access extends the amount
and length of time other drugs are active in the
BLOOD circulation. The result may be an intensified
effect of the drug or an ADVERSE REACTION. For
example, drinking while taking antihypertensive
medications to treat HYPERTENSION (high BLOOD
PRESSURE) may cause blood pressure to drop lower
than intended, resulting in dizziness or unsteadiness,
especially when standing up after lying
down (orthostatic HYPOTENSION).
In the long term, chronic alcohol abuse causes
the liver to increase activation of CYP450
enzymes, resulting in more rapid metabolism of
drugs. The result may be lower levels of drugs in
the blood circulation than are necessary to provide
therapeutic effects. With antihypertensive medications,
for example, this might mean blood pressure
remains elevated beyond the level expected
for the DOSE of medication. The alteration of
enzyme activity may also metabolize drugs in
ways that cause toxicity. Adverse reactions are a
particular risk among people who regularly drink
alcohol but do not divulge the information to their
doctors or often to family members because denial
is a hallmark of ALCOHOLISM. Altered enzyme activity
may continue for weeks to months after stopping
alcohol consumption and may be a
permanent state when alcohol abuse has been
exceptionally long term (over decades).
Direct Interactions
between Alcohol and Other Drugs
Consumed alcohol may also directly compete for
or bind with neuroreceptors in the BRAIN in ways
that interfere with drugs that act on the CENTRAL
NERVOUS SYSTEM such as anesthetic agents, ANAL-
GESIC MEDICATIONS (PAIN relievers), ANTIDEPRESSANT
MEDICATIONS, ANTIANXIETY MEDICATIONS, MUSCLE
RELAXANT
MEDICATIONS, antiseizure medications,
ANTIPSYCHOTIC MEDICATIONS, ANTIHISTAMINE MEDICA-
TIONS, and hypnotics. The interaction often intensifies
side effects such as sleepiness, confusion, and
cognitive dysfunction.
Increased Risk for Liver Damage
As the body’s clearinghouse for drugs, the liver is
especially vulnerable to damage from toxic
byproducts of drug metabolism. Though the liver
has great capacity to restore itself, the double