Phthalates in Prescription Drugs
Some Medications Deliver High Doses
Until recently, most of the concern surrounding the health risks of
phthalates has focused on the use of these plasticizers in toys,
personal care products, food packaging, and medical equipment such as
intravenous tubing. A case report in 2004 raised the possibility that
certain prescription medications may also be a source of phthalate
exposure for some people [
EHP 112:751–753 (2004)].
That finding prompted a systematic investigation that links
phthalate-containing medications with high internal exposure to these
chemicals [
EHP 117:185–189; Hernández-Díaz et al.].
The 2004 case study pinpointed Asacol®, a medication for treating
ulcerative colitis, as a probable source of phthalate exposure. Asacol
is covered with an enteric coating of dibutyl phthalate (DBP) that
prevents the medication from degrading before it reaches the small
intestine. Concentrations of the main metabolite of DBP in the urine of
the case study subject corresponded to an uptake of DBP exceeding by
two orders of magnitude the 95th percentile reported by the Centers for
Disease Control and Prevention in the general population. The
concentrations also surpassed the reference dose established for DBP by
the U.S. Environmental Protection Agency (EPA) on the basis of animal
testing.
To assess possible links between phthalate-containing prescription
medication usage and excreted metabolites, the investigators searched
National Health and Nutrition Examination Survey (NHANES) data from
survey periods between 1999 and 2004 when urine samples were tested for
phthalate metabolites and participants were asked about their use of
prescription medications. Various enteric-coated medications identified
as likely to contain phthalates included mesalamine (the generic form
of Asacol), didanosine (an antiretroviral agent), omeprazole (which
inhibits gastric acid secretion), and theophylline (used to treat
asthma and other lung diseases).
Among the 6 documented mesalamine users, average urine
concentrations of DBP metabolites were 50 times higher than those of
nonusers. For 2 of the 6 mesalamine users, the DBP metabolite
concentrations pointed to uptake exceeding the EPA’s reference dose.
Users of the other phthalate-containing medications also had
significantly higher concentrations of some metabolites than did
nonusers, though the gaps between users and nonusers were considerably
smaller than for mesalamine. The NHANES data also showed that at least
3 women who reported taking phthalate-containing medications were
pregnant.
These findings call for more investigation, the authors write,
particularly because some phthalates cross the placenta and cause
reproductive and developmental effects in laboratory animals. In one
study of male infants, increasing prenatal exposure to background
levels of phthalates was associated with a decrease in the distance
between the anus and base of the penis, indicating incomplete male
reproductive development [
EHP 113:1056–1061 (2005)].
The authors of the new study write that phthalate-containing
medications are among some of the most widely prescribed drugs in the
United States, which implies that many people, including pregnant
women, may be exposed to high concentrations of phthalates.
originally published on http://www.ehponline.org