AT IPA 2016
SAN FRANCISCO (FRONTLINE MEDICAL NEWS) – Older patients prescribed citalopram had almost 12-fold higher odds of hip osteoporosis, compared with those prescribed fluoxetine, according to a large retrospective study at a tertiary bone health clinic.
Patients on fluoxetine also had the lowest levels of C-terminal cross-linked telopeptide of type 1 collagen (CTX), a biochemical marker of bone turnover, said Dr. Clodagh Power and associates at St. James’s Hospital in Dublin.
The results suggest that fluoxetine causes less bone resorption than other selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors, or tricyclic antidepressants and “may be a safer choice for a cohort already predisposed to poorer brain health,” the researchers concluded in a poster presented at the 18th Congress of the International Psychogeriatric Association.
Poor bone health correlates with both antidepressant therapy and depression itself. In the case of antidepressants, tricyclics might increase the risk of falls and fractures by blocking alpha-adrenergic, H1, and M3 receptors, while SSRIs are thought to reduce bone mass through selective blockade of 5-HTT. To evaluate the relative effects of individual antidepressants, the investigators compared bone mineral densities, T-scores, fracture histories, and CTX levels among 522 patients on antidepressants and 1,056 randomly selected controls from the same bone health clinic who were not taking antidepressants. The entire cohort averaged 67 years of age, and 79% were female. Compared with controls, patients on antidepressants tended to be older, had a 1.0 kg/m2 greater average mean body mass index, and were more often women, the researchers noted.
Even after controlling for these differences, patients on antidepressants had a 0.03 g/cm3 lower average bone mineral density than controls (95% confidence interval, 0.05-0.01; P = .002), and 2.2-fold greater odds of prior hip fracture (odds ratio, 1.7-2.8; 95% CI; P less than .001). Even patients on antidepressants who had never had a hip fracture had lower bone mineral density of the hip than controls (mean difference, 0.121 g/cm3; P less than .001). No relationship, however, was found between antidepressant therapy and spinal bone mineral density, the investigators said.
Analyses of T-scores suggested that individual antidepressants have different effects on bone health. Mirtazapine had the highest estimated odds of hip osteoporosis (2.3), compared with controls. In descending order, the remaining odds ratios were 2.0 for citalopram, 1.5 for tricyclic antidepressants, 1.4 for sertraline, and 1.3 for escitalopram, but only the odds ratio for citalopram reached statistical significance (95% CI, 1.3-2.9; P = .001). No apparent relationship was found between hip osteoporosis and exposure to paroxetine, venlafaxine, or duloxetine, while fluoxetine actually showed a protective effect (OR, 0.16; 95% CI, .04-0.69; P = .005).
Additional analyses supported the hypothesis that fluoxetine poses the least risk to bone health. In a head-to-head comparison, the odds of hip osteoporosis were 11.9 times higher among patients taking citalopram than those taking fluoxetine (95% CI, 2.7-52.2; P less than .001) Also, patients on fluoxetine had average CTX levels of 0.06, compared with 1.17 for controls (P = .06).
These findings “add to prior data that implicate antidepressants as adversely impacting bone health,” the researchers concluded, but the results also merit cautious interpretation, as “no single drug was identified as clearly causing a greater reduction in bone mineral density or increased risk of fracture.”
The investigators disclosed no external funding sources or conflicts of interest.
