Paxil may Interfere with Breast Cancer Treatments

Readers of the blog are familiar with reports linking <"">Paxil (generic: Paroxetine) with adverse health events. Now, Reuters reports that antidepressant medication might interfere with breast cancer treatments. According to researchers in Canada, interference could cause patients to relapse and die, said Reuters.

The researchers found that those women taking Paxil, which is manufactured by GlaxoSmithKline, and who were also taking tamoxifen for treatment of their breast cancer, were more likely to die from breast cancer, said Reuters. The longer the patients were on both medications, said the researchers, reporting in the British Medical Journal, the more likely their chances of death, according to Reuters.

The researchers believe that Paxil interferes with the compound in the body that processes tamoxifen, reported Reuters. “There is probably a better choice of antidepressants for women taking tamoxifen but (any change) should be done gradually with a doctor,” said Dr. David Juurlink of the Institute for Clinical
Evaluative Sciences and Sunnybrook Health Sciences Center in Toronto, quoted Reuters. “People shouldn’t be stopping their tamoxifen. It is an extremely important medication,” nor should anyone abruptly cease taking Paxil without speaking to a doctor, Juurlink said. There are dangers with quickly stopping anti-depressant therapy, said Reuters.

The team looked at 2,430 breast cancer patients’ healthcare records; patients were aged 66 or older and took tamoxifen between 1993 and 2005, said Reuters. Thirty percent took an antidepressant—most popularly, paroxetine—at some point during tamoxifen treatment, wrote Reuters. Of these, 15 percent died during the study. “In contrast, no such risk was seen with other antidepressants,” the researchers wrote reported Reuters. Women taking Paxil and tamoxifen together for a one-quarter of their treatment time were 25 percent likelier to succumb to breast cancer, said Reuters. This figure increased to a striking 91 percent for women taking tamoxifen and Paxil together for 75 percent of their treatment time, added Reuters.
Tamoxifen is known to reduce the return of breast cancer by 50 percent if taken for five years and requires break down by an enzyme called CYP2D6; SSRI antidepressants (selective serotonin reuptake inhibitors) can interfere with CYP2D6.

“Paxil is a fairly potent inhibitor of that enzyme,” Juurlink said. “These results highlight a drug interaction that is extremely common, widely underappreciated, and potentially life-threatening, yet uniformly avoidable,” Juurlink said, quoted Reuters.
Very recently, according to Reuters Health, expectant mothers taking certain antidepressant or anti anxiety medications could experience increased risks for premature births and birth complications. CBC News wrote that mothers who have recently given birth and taking SSRIs might experience breast-feeding difficulties.

In October we wrote that women taking SSRIs during pregnancy may be likelier to experience premature birth and that babies born to women taking SSRIs were likelier to be admitted to an intensive care unit. In November we wrote about a Science Daily article on the likelihood of premature child delivery tripling in pregnant women with a history of depression and who take certain psychiatric drugs. In that study, researchers found that the medication-depression combination, when present before or during pregnancy, was significantly associated to childbirth earlier than at 35 weeks’ gestation.

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