Phenindione is a synthetic indandione-class oral anticoagulant active pharmaceutical ingredient (API). Chemically identified as 2-phenyl-1,3-indandione, it belongs to the vitamin K antagonist class of anticoagulants and has pharmacological activity similar in principle to other vitamin K antagonists. Phenindione has historically been used for anticoagulant therapy, although its clinical use has become limited because of safety considerations and the availability of other anticoagulant options.
Phenindione has the CAS Number 83-12-5, molecular formula C₁₅H₁₀O₂, and molecular weight 222.24 g/mol. The identity is also recorded by NIST, which reports a molecular weight of 222.2387 g/mol.
Phenindione is also known by names including 2-Phenyl-1,3-indandione, Phenylindione, Pindione, Rectadione, and Fenindione. Its IUPAC name is 2-phenylindene-1,3-dione. PubChem identifies it as a beta-diketone and aromatic ketone and lists the compound under PubChem CID 4760.
The compound is a neutral, achiral small molecule with no defined stereocenters. Its calculated molecular properties include an XLogP3 value of approximately 2.9, hydrogen-bond donor count of 0, hydrogen-bond acceptor count of 2, and topological polar surface area of approximately 34.1 Ų.
Phenindione is reported as a white to creamy-white crystalline material or crystalline powder. Published physicochemical references report a melting range around 148–151°C, while individual literature and commercial reference sources may report slightly different ranges depending on the material and test method.
Phenindione has historically been used as an oral anticoagulant for conditions requiring reduction of blood coagulation. Its anticoagulant action is associated with interference with vitamin K-dependent coagulation factor synthesis. This reduces the formation of active coagulation factors and consequently decreases thrombin generation.
Historical pharmaceutical applications have included anticoagulant therapy and prophylaxis in thromboembolic conditions. PubChem records historical use in conditions including pulmonary embolism, atrial fibrillation, cerebral embolism, mural thrombosis, and thrombophilia.
Because phenindione is an anticoagulant with clinically significant effects on coagulation, pharmaceutical development and manufacturing require stringent control of API identity, purity, potency, and batch-to-batch consistency.
Phenindione has a recognized British Pharmacopoeia monograph. The BP definition states that Phenindione contains not less than 98.0% and not more than 102.0% of C₁₅H₁₀O₂, calculated with reference to the dried substance. The BP monograph also specifies an identification test based on infrared absorption spectroscopy and includes a related-substances test by liquid chromatography.
The BP monograph gives a melting-point range of 148–151°C and describes Phenindione as very slightly soluble in water and slightly soluble in ethanol (96%) and ether. Solutions are reported as yellow to red.
These pharmacopoeial values are preferable to generic API specifications because they provide a recognized standard specifically for Phenindione. Parameters for which a universal numerical value cannot be established should remain specification-dependent rather than being populated with assumed limits.
Phenindione has relatively low aqueous solubility. PubChem reports an experimental solubility of approximately 27 mg/L at 20°C, while pharmacopoeial descriptions characterize it as very slightly soluble in water. It is more readily soluble in alkaline solutions and is reported to dissolve in solvents including methanol, ethanol, ether, acetone, benzene, and chloroform.
The reported pH of a saturated solution is approximately 4.5 at 25°C, but this should not be interpreted as a universal pharmaceutical API release specification for a 1% solution.
Phenindione API manufacturing requires controlled chemical processing followed by appropriate analytical testing. Important quality attributes include identification, assay, related substances, moisture, residual solvents, elemental impurities, and physical characteristics.
For a CMS specification table, it is important to distinguish pharmacopoeial numerical limits from general analytical parameters. The BP provides the strongest publicly verified numerical assay value of 98.0–102.0% on the dried substance basis. Generic values for heavy metals, individual impurities, total impurities, water content, or residue on ignition should not be inserted unless supported by the applicable approved specification.
Phenindione is therefore a well-characterized small-molecule anticoagulant API with CAS 83-12-5, molecular weight 222.24 g/mol, established pharmacopoeial identity, and a BP assay range suitable for pharmaceutical quality-control reference.
| 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 0.5% |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 0.5% |