Risedronate Sodium is a nitrogen-containing bisphosphonate active pharmaceutical ingredient used in medicines for the treatment and prevention of osteoporosis and other disorders associated with excessive bone resorption. It is a synthetic pyridinyl bisphosphonate that acts primarily as an antiresorptive agent by inhibiting osteoclast-mediated bone resorption.
Risedronate Sodium is used in pharmaceutical formulations for postmenopausal osteoporosis, osteoporosis in men, glucocorticoid-induced osteoporosis and Paget's disease of bone. Current U.S. labeling confirms these major therapeutic applications.
The API exists in different hydration states, including the monohydrate and hemi-pentahydrate forms. USP specifically requires the API label to identify which hydration form is present.
Risedronate Sodium is the monosodium salt of risedronic acid. The anhydrous sodium salt has the molecular formula C7H10NNaO7P2 and molecular weight 305.09 g/mol. The pharmaceutical API can occur as the monohydrate or hemi-pentahydrate.
The hemi-pentahydrate form has CAS No. 329003-65-8 and molecular weight 350.13 g/mol, while the monohydrate has CAS No. 353228-19-0 and molecular weight 323.12 g/mol. The generic risedronate sodium substance is also listed under CAS 115436-72-1.
Risedronate Sodium is a white to off-white crystalline powder. It is soluble in water and aqueous solutions and is essentially insoluble in common organic solvents.
Risedronate Sodium belongs to the pyridinyl class of nitrogen-containing bisphosphonates. Its structure contains two phosphonate groups attached to a carbon center bearing a hydroxyl group and a pyridinyl-containing side chain. The high affinity of bisphosphonates for bone mineral allows risedronate to localize at hydroxyapatite surfaces.
At the cellular level, risedronate inhibits osteoclast activity and reduces bone resorption. Its pharmacological activity is associated with inhibition of farnesyl pyrophosphate synthase in the mevalonate pathway, affecting the prenylation of proteins required for normal osteoclast function.
The hydration state of Risedronate Sodium is an important pharmaceutical-quality attribute. USP recognizes both monohydrate and hemi-pentahydrate forms and applies different water/volatile-content controls to these forms.
Risedronate Sodium API is primarily used for the manufacture of oral bisphosphonate medicines.
Its pharmaceutical applications include:
U.S. prescribing information confirms risedronate sodium's use in osteoporosis and Paget's disease, with its mechanism based on inhibition of osteoclast-mediated bone resorption.
Risedronate Sodium is available in immediate-release and delayed-release oral pharmaceutical formulations, with different strengths used according to the therapeutic indication.
Risedronate Sodium requires careful quality control because the API can exist in different hydration states. USP provides specific requirements for identification, assay, organic impurities and water/volatile content according to the applicable hydrate form.
Analytical testing may include:
The USP assay requirement for Risedronate Sodium is 98.0–102.0% of risedronate sodium. For the monohydrate this is calculated on the dried basis, while for the hemi-pentahydrate it is calculated on the anhydrous basis.
USP also specifies 11.9–13.9% water for material labeled as the hemi-pentahydrate and 5.5–7.5% loss on drying for material labeled as the monohydrate.
Risedronate Sodium is a well-established bisphosphonate API requiring controlled chemical purity, impurity profile and hydration state.
A pharmaceutical-grade Risedronate Sodium manufacturing program should focus on:
The USP monograph specifically requires labeling to identify whether the material is the monohydrate or hemi-pentahydrate, making hydration-state control particularly important for API quality.
Risedronate Sodium should be packaged in suitable well-closed pharmaceutical containers that protect the material from contamination and uncontrolled environmental exposure.
USP specifies well-closed containers and storage at room temperature for the API.
Because hydration state is an important characteristic of Risedronate Sodium, packaging should also help maintain the validated moisture condition of the API throughout storage and transportation.
Risedronate Sodium API documentation may include:
A complete technical package helps pharmaceutical manufacturers evaluate API identity, purity, hydration state and suitability for formulation development.
Risedronate Sodium is an established nitrogen-containing bisphosphonate API with extensive pharmaceutical use in osteoporosis and Paget's disease. Its established pharmacology and USP monograph make it an important pharmaceutical ingredient for oral antiresorptive formulations.
A quality-focused Risedronate Sodium API program should provide:
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | 5.5–7.5% |
| Heavy Metals | NMT 10 ppm |
| Individual Impurity | NMT 0.10% |
| Total Impurities | NMT 0.50% |
| Water Content | 11.9–13.9% |