308 Morphine
perseded that antianxiety function of morphine. Somewhat surprisingly, given
morphine’s depressant actions, researchers have found the drug can improve
performance on a test of response time in decision making. Other researchers
have found no effect on performance in tests of memory, reasoning, muscular
coordination, and various additional skills basic to everyday living. Few ill
effects seem to come from chronic use of pure morphine (as opposed to adul-
terated street supplies). Addicts with access to the pure product have lived
healthy and productive lives into old age. As drug laws tightened over the
past century, use of morphine by ordinary middle-class people declined, shift-
ing the prevalence of nonmedical morphine usage from law-abiding persons
into populations with more social deviance. Consequently, illicit use of mor-
phine became more associated with society’s outcasts. That association, how-
ever, was caused by changes in laws and social attitudes (changes in setting),
not by any chemical effect of the drug.
Drug interactions.Animal and human experiments show that more pain
relief can come from morphine ifephedrineis taken at the same time.Dex-
troamphetaminecan improve pain relief provided by morphine.Alcohol, tri-
cyclic antidepressants, and monoamine oxidase inhibitors (MAOIs, found in
some antidepressants and other medicine) can boost morphine effects. Rat
experiments indicate that benzodiazepine class depressants lengthen the effect
from a morphine dose. Researchers find that morphine andnicotinehave
cross-tolerance in mice.
Cancer.Morphine is not known to cause cancer. Some laboratory tests and
some studies of human users, however, detect cell damage that could lead to
cancer. Some people smoke morphine, and the smoke is suspected of causing
esophageal cancer. Evidence exists that naturally occurring morphine in lung
tissue may constrain development of lung cancer, that nicotine counteracts
such protection, and that tobacco smokers have more naturally occurring mor-
phine in their lung tissue than nonsmokers (perhaps because the body in-
creases morphine production when challenged by nicotine). All this evidence,
however, involves minute levels of naturally occurring morphine in the body
and does not support taking the drug in hopes of avoiding lung cancer.
Pregnancy.When given in amounts exceeding normal human medical doses
by hundreds of times, morphine has caused animal birth defects. Malforma-
tions involving bones and soft tissues have been observed in animals. Preg-
nant rats and hamsters dosed on morphine produce male offspring that exhibit
feminized behavior. When morphine was routinely given to male adolescent
rats, the drug seemed to interfere with sexual maturation. As their offspring
reached adulthood, they appeared normal but had hormone abnormalities.
In humans no increase in birth defects has been observed in offspring of
women who used morphine during pregnancy. A morphine dose quickly
passes from the woman into the fetus, however, and reaches a blood level
similar to the woman’s. A dose lasts longer in the fetus than elsewhere in a
woman’s body. The drug reduces fetal motions. A baby born to a chronic
morphine user can have dependence on the drug and exhibit withdrawal
symptoms after birth. One study found that infants receiving morphine for
medical purposes soon after birth show no ill effects five years later in con-
duct, muscular coordination, or intelligence.