QUS in monitoring raloxifene and estrogen-progestogens: a 4-year longitudinal study

Three-year prospective study on fracture risk in postmenopausal women by quantitative ultrasound at the phalanges

The purpose of this study was the calculation of fracture risk in a prospective study on postmenopausal women by quantitative ultrasound (QUS) at the phalanges. A total of 2341 postmenopausal women were recruited in 5 centers in Italy during 2006 and 2007 for QUS measurement during a screening program for osteoporosis. Two ultrasound parameters were collected: amplitude-dependent speed of sound (AD-SoS) and ultrasound bone profile index (UBPI). Women were then recontacted in 2010 and were asked about fracture occurrence during the period since previous QUS measurement. Data about new fracture occurred in this period, site and cause of fracture were requested. Two thousand two hundred eleven women were successfully recontacted. Mean age of the recruited women was 60.9 ± 10.0 yr, mean age at menopause was 49.3 ± 4.4 yr, mean body mass index (BMI) was 26.5 ± 4.6 kg/m². A total number of 108 new major osteoporotic fractures occurred during the 3-yr period, of which 23 are hip fractures, 51 are vertebral fractures. Relative risk (RR) per standard deviation (SD) decrease for major fractures was 1.77 (confidence interval [CI]: 1.59-1.97) for AD-SoS and 2.06 (CI: 1.78-2.37) for UBPI. When corrected for age, BMI, age at menopause, the RRs are still significant and equal to 1.44 (CI: 1.26-1.65) for AD-SoS and 1.67 (CI: 1.39-2.00) for UBPI. RR for vertebral fractures was 1.63 (CI: 1.41-1.88) for AD-SoS and 1.73 (CI: 1.44-2.08) for UBPI. RR for hip fractures was 1.92 (CI: 1.55-2.37) for AD-SoS and 2.68 (CI: 1.86-3.86) for UBPI. Ultrasound parameters AD-SoS and UBPI are able to significantly predict future major fractures in a prospective cohort of more than 2000 postmenopausal women.

Organic anion transporting polypeptides OATP1B1 and OATP1B3 and their genetic variants influence the pharmacokinetics and pharmacodynamics of raloxifene

Background

Raloxifene, a selective estrogen receptor modulator, exhibits quite large and unexplained interindividual variability in pharmacokinetics and pharmacodynamics. The aim of this study was to determine the role of organic-anion transporting polypeptides OATP1B1 and OATP1B3 and their genetic variants in the pharmacokinetics and pharmacodynamics of raloxifene.

Methods

To test the role of OATP1B1 and OATP1B3 transporters on hepatic uptake of raloxifene and its metabolites an in vitro model of Chinese Hamster Ovary cells expressing OATP1B1 or OATP1B3 was employed. The influence of OATP1B1 and OATP1B3 genetic variants on in vivo pharmacokinetics and pharmacodynamics was evaluated in 53 osteoporotic postmenopausal women treated with raloxifene.

Results

Our in vitro results showed that raloxifene and two of the three metabolites, raloxifene-4'-β-glucuronide (M2) and raloxifene-6,4'-diglucuronide (M3), interact with OATP1B1 and OATP1B3. Higher M3 and total raloxifene serum concentrations in patients correlated with lower serum levels of bone resorption marker, serum C-terminal telopeptide fragments of type I collagen, indicating a higher antiresorptive effect of raloxifene. Higher concentrations of M2 correlated with higher increase of lumbar spine bone mineral density supporting the raloxifene vertebral fracture specific protection effect. Finally, raloxifene, M3 and total raloxifene serum concentrations were significantly higher in patients with SLCO1B1 c.388A > G polymorphism and *1b haplotype implicating a considerable genetic effect on pharmacokinetics and pharmacodynamics of raloxifene.

Conclusions

These findings indicate that SLCO1B1 c.388A > G polymorphism could play an important role in pharmacokinetics and pharmacodynamics of raloxifene.

Performance of quantitative ultrasound measurements of bone for monitoring raloxifene therapy

Raloxifene increases bone mineral density (BMD) and decreases vertebral fracture risk; the effects on quantitative ultrasound (QUS) variables, however, have been less well studied. We aimed to further evaluate the effectiveness of QUS for monitoring raloxifene treatment and withdrawal effects. Osteopenic, postmenopausal women (age=50-80 yr, n=125), who completed a 96-wk study (phase A) evaluating treatment compliance or monitoring, were invited to participate in a 96-wk raloxifene withdrawal study (phase B). Those originally receiving treatment were then randomized to continue on raloxifene (60 mg/d)+calcium (500 mg/d) (n=23) or to discontinue raloxifene and take placebo+calcium (500 mg/d) (n=23). Previously untreated women remained untreated (n=12). Yearly QUS and BMD measurements were performed. At the end of phase A, lumbar spine BMD (p=0.005), amplitude-dependent speed of sound (Ad-SoS) (p=0.006) and average SoS (p=0.040) decreased in untreated women but remained stable in treated women. Significant changes in Ad-SoS and ultrasonic bone profiler index had occurred in treated women by the end of phase B (p<0.01). All variables, except bone transmission time, were higher for those receiving any raloxifene treatment (p<0.05). Until further knowledge has been acquired, QUS measurement variables should only be used in conjunction with BMD when assessing changes in bone because of raloxifene therapy.

Quantitative ultrasound in osteoporosis and bone metabolism pathologies

Quantitative ultrasound (QUS) has been introduced in the medical field for the study of bone tissue to identify changes in the tissue that could suggest the presence of osteoporosis and bone fragility. The ultrasound technique is simple, versatile, and its low cost and lack of ionizing radiation have led to the diffusion of this method worldwide. The present article is an overview of the most relevant developments in the field of quantitative ultrasound, in clinical and experimental settings. The advantages and limitations of the present technique and suggestions for its use in the clinical practice are reported.

Quantitative ultrasound in the assessment of skeletal status

Quantitative ultrasound (QUS) is a non-invasive technique for the investigation of bone tissue in several pathologies and clinical conditions, especially in the field of osteoporosis. The versatility of the technique, its low cost and lack of ionising radiation have led to the diffusion of this method worldwide. Several studies have been conducted in the last years to investigate the potential of QUS in multiple areas with promising results; the technique has been applied in the prediction of osteoporotic fractures, in monitoring therapies, in the investigation of secondary osteoporosis, in paediatrics, neonatology and genetics. Our review article gives an overview of the most relevant developments in the field of quantitative ultrasound, both in clinical and in experimental settings.

Quantitative ultrasound at the phalanges in monitoring alendronate therapy

This study evaluated the efficacy of quantitative ultrasound (QUS) at the phalanges in monitoring alendronate treatment. Seventy-nine postmenopausal women were enrolled: 46 subjects entered therapy with alendronate, the remaining 33 did not follow any therapeutic regimen. All subjects underwent phalangeal ultrasound measurement before starting treatment and after 12 mo. Two QUS parameters were measured: AD-SoS (Amplitude Dependent Speed of Sound) in m/s, and BTT (Bone Transmission Time) in micros. Mean age of subjects at the beginning of the study was 58.7 +/- 6.5 y, mean BMI was 26.6 +/- 4.4 kg/m(2), mean time since menopause was 6.7 +/- 5.0 y; no significant differences could be observed between the groups (p > 0.05). At 12-mo follow-up a significant increase of both QUS parameters was observed: +18.8 +/- 24.4 m/s for AD-SoS, p < 0.0001; +0.05 +/- 0.08 micros for BTT, p < 0.001. In the nontreated group AD-SoS was stable (+1.0 +/- 33.7 m/s), as well as BTT (-0.07 +/- 0.25 micros), p = n.s. for both. In the treated group the percentage of responders was 65.2% for AD-SoS and 50.0% for BTT. The percentage of non responders was 13% for AD-SoS and 15.2% for BTT. The results confirm that the effect of alendronate treatment may be suggested by QUS at the phalanges after 12 mo of treatment.