Codeine 103none. Although no direct observations have noted codeine causing cancer in
rats or mice, computer analysis of data from some experiments indicates that
the drug may cause cancer in rodents. The human body produces very small
amounts of codeine naturally, and researchers suspect this naturally occurring
codeine may deter development of lung cancer; but those natural processes
do not mean that doses of the drug would help prevent cancer.
Pregnancy.Whether codeine causes birth defects is unknown. It produced
no evidence of malformations when given to pregnant rats and rabbits. Co-
deine reduced fetal weight in mice and hamsters in one experiment but did
not increase the normal rate of defects in mice, nor was a statistically signif-
icant change in malformation rate observed in hamsters. Investigators running
another mice experiment, however, concluded that codeine does cause as-
sorted malformations. Researchers seeking evidence about various human
birth defects examined medical records of 100 to 199 women who used a
cough remedy containing codeine and found that none of the offspring had
any of the congenital abnormalities being investigated. Suspicion exists that
codeine may cause cleft palate and cleft lip in humans, but birth defects are
considered unlikely if the drug is used during pregnancy. A pregnant woman
who takes codeine can produce an infant who is dependent on that drug and
who undergoes a withdrawal syndrome upon birth.
Codeine passes into the milk of nursing mothers, but researchers find its
level and that of its metabolite morphine to be acceptable if the woman is
using codeine moderately. Nonetheless, nursing mothers are advised to avoid
codeine because mechanisms that break down codeine in the body are incom-
pletely formed in newborns, causing them to react more strongly to the drug
than older children or adults.
Additional scientific information may be found in:
Eggen, A.E., and M. Andrew. “Use of Codeine Analgesics in a General Population. A
Norwegian Study of Moderately Strong Analgesics.”European Journal of Clinical
Pharmacology46 (1994): 491–96.
Mattoo, S.K., et al. “Abuse of Codeine-Containing Cough Syrups: A Report from In-
dia.”Addiction92 (1997): 1783–87.
Romach, M.K., et al. “Long-Term Codeine Use Is Associated with Depressive Symp-
toms.”Journal of Clinical Psychopharmacology19 (1999): 373–76.
Rowden, A.M., and J.R. Lopez. “Codeine Addiction.”DICP: The Annals of Pharmaco-
therapy23 (1989): 475–77.
Sproule, B.A., et al. “Characteristics of Dependent and Nondependent Regular Users
of Codeine.”Journal of Clinical Psychopharmacology19 (1999): 367–72.