Purpose: Strontium salts may provide support for bone health and treatment for osteoporosis, but the safety and effectiveness of these salts is not completely understood. The aim of this clinical study (NCT03761979) was to obtain safety and pharmacokinetic information following acute oral intakes of three ascending doses of strontium L-lactate by healthy adults.

Subject methods: Ten healthy men and women, mean age 43 ± 2 years, ingested one of three ascending doses of strontium L-lactate (SrLac) once per week for three weeks in succession. All subjects were administered the Study Product in a sequential manner such that the lowest amount (170 mg Sr) was provided at Visit 2, the next highest amount (340 mg Sr) was provided at Visit 3, and the highest amount (680 mg Sr) was provided at Visit 4. At each visit, fasting blood collections were performed pre-dose and 1, 2, 3, 4, 5, 6, 8 and 12 hours’ post-dose to determine serum strontium at each interval.

Results: The pharmacokinetics related to each of three doses of SrLac that were administered to fasted subjects were similar to the findings for other strontium salts. At a dose of 170 mg strontium, a mean serum Cmax of 2.6 ± 0.6 mg Sr/dL was observed about 3.1 h after ingestion. A dose of 340 mg strontium exhibited a mean serum Cmax of 6.4 ± 1.8 mg Sr/dL about 3.2 h after ingestion. At a dose of 680 mg strontium, a mean serum Cmax of 9.3 ± 2.1 mg Sr/dL was observed about 2.8 h after ingestion. Oral bioavailability was high, reflecting the high solubility of SrLac in water and intestinal fluid. The data suggest that between 27% and 34% of the administered dose was absorbed. At these doses, no strontium-related adverse effects were observed.

Conclusion: This clinical study in 10 normal adults (50% females) showed that the strontium ion in SrLac is readily bioavailable after oral administration. The intervention was conducted per study protocol, and no clinically significant protocol deviations occurred. Pharmacokinetic data indicated that doses of 170 and 340 mg strontium provided serum strontium concentrations in ranges known to be beneficial for the treatment of low bone density of osteoporosis and osteopenia. No product-related adverse events were observed.