Strontium ranelate

In in vitro studies, strontium ranelate:

• stimulates bone formation in bone culture, and also stimulates the replication of osteoblast precursors and collagen synthesis in bone culture;
• reduces bone resorption by suppressing the differentiation of osteoclasts, as well as their resorptive activity. As a result of the action of the drug, the balance between the formation and destruction of bone tissue changes towards the processes of bone formation.
• The activity of strontium ranelate has been studied experimentally using various preclinical models. In particular, in experiments on intact rats, the use of strontium ranelate led to an increase in the trabecular bone mass, the number of trabeculae and their thickness, as a result of which the mechanical properties of the bone improved.

In the bone tissue of humans and experimental animals to whom the drug was prescribed, strontium ranelate was mainly absorbed on the surface of hydroxyapatite crystals and only to a small extent replaced calcium in these crystals in the newly formed bone.

Strontium ranelate does not alter the characteristics of bone crystals. According to the biopsy of the iliac crest, carried out after treatment with strontium ranelate at a dose of 2 g per day for up to 60 months in clinical studies, no adverse effect on bone quality or mineralization was found.

The combined effects of strontium distribution in bone tissue and increased absorption of X-rays by strontium compared to calcium lead to an increase in bone mineral density (BMD), which is measured by two-photon X-ray absorptiometry.

The data obtained to date indicate that these factors account for approximately 50% of the increase in the BMD index after 3 years of treatment with strontium ranelate at a dose of 2 g / day. These data should be taken into account when interpreting changes in the BMD index during treatment with strontium ranelate.

In clinical studies that confirmed the ability of strontium ranelate to reduce the risk of fractures, the mean BMD value increased in the group of patients treated with strontium ranelate compared with the baseline value - for the lumbar vertebrae by about 4% per year, and for the femoral neck by 2% per year; after 3 years, the increase in BMD was 13-15% and 5-6%, respectively (according to various studies).

Starting from the third month of therapy and within 3 years of follow-up, there was an increase in the indicators of biochemical markers of bone formation (bone fraction of alkaline phosphatase (ALP) and C-terminal propeptide of type I procollagen) and a decrease in indicators of bone resorption markers (cross-linked C-terminal and N-terminal telopeptides in urine) versus placebo.

For strontium ranelate, the secondary effect in relation to the main pharmacological properties is a slight decrease in serum concentrations of calcium and parathyroid hormone, as well as an increase in the concentration of phosphorus in the blood and the activity of total alkaline phosphatase, which, however, is not accompanied by any clinical effects.

Risk factors for postmenopausal osteoporosis are decreased bone mass, decreased BMD, early menopause, a history of smoking and family history of osteoporosis.

One of the most clinically significant complications of osteoporosis is the development of fractures, and the risk of fractures increases with an increase in the number of risk factors.