Pamidronic Acid is a nitrogen-containing bisphosphonate and an important active pharmaceutical ingredient associated with inhibition of bone resorption. It is chemically identified as (3-amino-1-hydroxypropane-1,1-diyl)bis(phosphonic acid) and is also known as pamidronate or 3-amino-1-hydroxypropylidene-1,1-bisphosphonic acid. The substance has CAS Number 40391-99-9, molecular formula C₃H₁₁NO₇P₂, and molecular weight 235.07 g/mol.
PubChem reports an experimental melting-point range of 254–262°C and aqueous solubility of approximately 15.8 g/L. These are reference physical-property values and should not automatically be treated as API release specifications.
Pamidronic Acid is primarily associated with bisphosphonate pharmaceutical development and is the parent acid corresponding to pamidronate salts. Pamidronate pharmacology is based on inhibition of osteoclast-mediated bone resorption and interaction with bone mineral, particularly hydroxyapatite.
The clinically marketed pharmaceutical form is generally pamidronate disodium, rather than the free acid. Current U.S. labeling identifies pamidronate disodium for moderate or severe hypercalcemia associated with malignancy, moderate to severe Paget's disease of bone, and osteolytic bone metastases of breast cancer or osteolytic lesions of multiple myeloma.
Pamidronate belongs to the bisphosphonate class and has a strong affinity for calcium phosphate mineral in bone. Pamidronate can adsorb onto hydroxyapatite crystals and inhibit osteoclast activity, thereby reducing bone resorption. The corresponding pharmaceutical salt is used clinically for conditions in which excessive osteoclastic bone resorption contributes to disease pathology.
Pamidronic Acid API requires controlled manufacturing and analytical characterization because phosphonic-acid compounds can present challenging chromatographic and impurity-analysis requirements. Appropriate quality-control programs may include identity testing, chromatographic assay, related-substance analysis, water determination, elemental impurities, residual-solvent testing and microbiological quality testing where applicable.
Publicly available commercial specifications report assay values of approximately NLT 98.0% or higher and loss-on-drying limits around NMT 1.0–2.0%, but these should be regarded as product-specific specifications rather than universal pharmacopoeial limits.
Identity can be established using spectroscopic and chromatographic techniques, including IR/NMR and chromatographic retention-time comparison. HPLC or suitable ion/chromatographic methods can be used for assay and related-substance determination. Published analytical research has demonstrated chromatographic determination of pamidronate and related phosphorus-containing impurities.
Typical pharmaceutical API documentation may include Certificate of Analysis, Safety Data Sheet, specification sheet, analytical method information, stability information and manufacturing-quality documentation, depending on the intended regulatory market.
Important: Pamidronic Acid should not be confused with Pamidronate Disodium. Pamidronate disodium has CAS 57248-88-1 and molecular weight 279.03 g/mol for the anhydrous salt, while pamidronic acid has CAS 40391-99-9 and molecular weight 235.07 g/mol.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.1% |
| Heavy Metals | NMT 20 ppm |
| Individual Impurity | NMT 0.10% |
| Total Impurities | NMT 0.50% |
| Water Content | NMT 1.0% |
| Melting Point | 254–262°C |