The product identified as VD3 powder/oil,injection Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable is cholecalciferol, a secosteroid chemically designated as (3β,5Z,7E)-9,10-secocholesta-5,7,10(19)-trien-3-ol. The molecular formula is C₂₇H₄₄O, the molecular weight is 384.64 g/mol, and the CAS registry number is 67-97-0. The crystalline powder grade is released against the Ph. Eur. monograph 0072, the current USP–NF Cholecalciferol monograph, and the JP Cholecalciferol monograph when regional compliance is required. Assay and related substances are determined by liquid chromatography using Ph. Eur. 2.2.29 or USP <621>; the compendial assay acceptance range for the crystalline form is 97.0–103.0% on the dried basis. The theoretical potency of pure cholecalciferol is 40 IU/μg, equivalent to 40 MIU/g; therefore an oily pharmaceutical concentrate labelled 1.0 MIU/g contains 25 mg/g cholecalciferol, and a 1.7 MIU/g concentrate contains 42.5 mg/g. The product is manufactured under a quality system aligned with ICH Q7 for active pharmaceutical ingredients, and residual solvents, elemental impurities, and microbial quality are controlled according to ICH Q3C, ICH Q3D, and the applicable pharmacopoeial general methods. The three presentations—crystalline powder, oily concentrate, and injection-grade powder or oil—are unformulated APIs intended for downstream processing into oral solid, oral liquid, and injectable finished dosage forms.

How Do the Powder, Oil and Injection-Grade Inputs Differ in Control Strategy?

The crystalline powder is supplied as a white or almost white crystalline solid. It is practically insoluble in water and soluble in fatty oils and ethanol, a solubility profile that governs formulation route selection. Particle size is not assigned a fixed limit in the cholecalciferol monograph; it is controlled by the applicant or manufacturer using laser diffraction per USP <429>, and the specification is normally selected to match the intended blending platform. Loss on drying is reported by Ph. Eur. 2.2.32, and residual solvents are tested by Ph. Eur. 2.4.24 or USP <467>. The oily concentrate is prepared by dissolving crystalline cholecalciferol in medium-chain triglycerides or a refined vegetable oil under nitrogen. Its release specification includes assay by HPLC, peroxide value per Ph. Eur. 2.5.5, acid value per Ph. Eur. 2.5.1, and visual clarity. The injection-grade presentation retains the same assay and identity standards but adds a dose-based bacterial endotoxin limit determined according to Ph. Eur. 5.1.10 and tested by Ph. Eur. 2.6.14 or USP <85>. Sterility is not an API release attribute for a water-insoluble solid; it is established during finished injection manufacture by terminal sterilisation or aseptic processing.

In oral solid dosage manufacture, blend uniformity is the limiting acceptance criterion because the API is present at microgram levels. A 400 IU dose corresponds to only 10 μg of cholecalciferol, so direct addition of crystalline powder to a high-shear mixer creates segregation and electrostatic adhesion risk. The powder is therefore pre-blended as a 1:10 or 1:100 trituration with microcrystalline cellulose, pregelatinized starch, or calcium hydrogen phosphate dihydrate. The trituration is screened through a 500 μm or 250 μm sieve before bin blending. Wet granulation can be used when light exposure and granule drying conditions are controlled. The compendial melting range of cholecalciferol is 82–87 °C; production-scale fluid-bed dryers should operate at inlet temperatures safely below that region to avoid local melting and related-substance formation. Dry granulation by roller compaction is an alternative that avoids aqueous contact but can increase hydrophobic surface coating. Published data for this specific roller-compacted configuration is limited, so process qualification must include blend uniformity, assay distribution, and degradation product monitoring.

When Cholecalciferol Oil Is Selected for Oral Liquid and Softgel Processes

The oily concentrate is selected when the target dosage form is a softgel, an oral drop, or an oil-based liquid. The 1.0 MIU/g concentrate is normally diluted with medium-chain triglycerides to a final fill weight determined by capsule fill volume and label claim. Fill weight is directly proportional to potency; rotary die softgel machines therefore require continuous in-line viscosity and fill-weight monitoring. The lower viscosity of medium-chain triglycerides, typically 25–33 mPa·s at 20 °C, improves ribbon flow, but the same vehicle can migrate through the gelatin shell if the shell plasticizer system is not selected correctly. Long-chain triglycerides have higher viscosity and lower migration tendency, but their peroxide content must be controlled before heat exposure. The concentrate should be blanketed with nitrogen during storage and mixed under low-shear conditions. On a rotary die softgel line, fill material that cools below 25 °C in the hopper may show viscosity drift and fill-weight variability; therefore jacketed hoppers with recirculating water and intermittent nitrogen sparging are used. Ribbon thickness is die-size dependent but is commonly maintained at 0.7–0.9 mm for standard oval softgel tooling. Recrystallized cholecalciferol in the oil phase, if not detected, can cause potency non-uniformity; microscopy or laser diffraction is used to confirm the absence of visible crystals and to detect temperature cycling damage.

Injectable Processing Requires Dose-Based Endotoxin Limits Rather Than a Default API Assay

Cholecalciferol is practically insoluble in water; injectable formulations therefore require a parenteral-grade oil, a co-solvent-surfactant system, or a liposomal, micellar, or emulsion-based design. The injection-grade API is not sterile solely because it is described as injection-grade. It is supplied with reduced bioburden and a documented endotoxin limit derived from the maximum daily dose and route of administration. The calculation follows the framework of Ph. Eur. 5.1.10 or USP <85>, and batch release data are generated by Ph. Eur. 2.6.14. Oil-based injections require endotoxin testing of the vehicle as well as the API because endotoxin can partition unpredictably in lipid systems. Particulate matter in the finished injection is a formulation-level obligation under USP <788>, but the API supplier can reduce particle load through controlled crystallisation and micronization. Terminal sterilisation of oily injections by dry heat is possible only if the formulation tolerates the time–temperature profile; otherwise aseptic filtration of an oil or co-solvent solution is used with pre-sterilized containers. Published data for endotoxin recovery from every lipid-based formulation is limited, so method suitability must be established for each finished product.

Oxidative and Photo-Degradation Stability Boundaries in Solid and Oily Matrices

Cholecalciferol degrades primarily by photoisomerization to pre-cholecalciferol and by oxidation through the triene system. The crystalline material is less sensitive than the oil-diluted form because the drug substance has limited surface area and is not dispersed in an oxidizable triglyceride matrix; however, both require protection from light and oxygen. Bulk containers must be airtight and light-resistant. In oily concentrates, antioxidant addition is a formulation decision; the raw API is not normally supplied with a protective antioxidant unless stated in the drug master file. When tocopherol or butylated hydroxytoluene is used, the concentration must be justified by stability data and must not interfere with the HPLC assay. Elevated temperatures during softgel encapsulation or hot-melt processing can accelerate peroxide formation; processing hold times at temperatures above 40 °C should be minimized, and peroxide value should be measured before and after the hold. In solid forms, neutral aqueous granulating fluids are generally preferred because strongly acidic or alkaline conditions can promote isomerization; published data for this specific pH-dependent degradation in a standard granulation is limited. If the crystalline powder is exposed to relative humidity above 60%, pre-drying is required before gravimetric dispensing because adsorbed water can affect electrostatic behaviour and assay uniformity. Milling operations should be conducted under nitrogen and light protection; local temperature excursions during micronization must be controlled to remain below the cholecalciferol melting range.

Across Comparable Vitamin D Sources and Carrier-Modified Forms

Compared with ergocalciferol, CAS 50-14-6, C₂₈H₄₄O, molecular weight 396.65 g/mol, cholecalciferol has a different side-chain structure and separate pharmacopoeial monographs. The two compounds produce distinct HPLC retention times and are not interchangeable without revalidation of analytical methods, process qualification, and regulatory assessment. Feed-grade vitamin D3 is often diluted on vegetable carriers or silica and is produced under feed hygiene systems rather than ICH Q7 GMP for human APIs. It may contain carrier particles, antioxidants, and related sterols that fall outside Ph. Eur. 0072 impurity limits. Microencapsulated or spray-dried cholecalciferol beadlets are formulated intermediates, not unformulated APIs; they contain gelatin, starch, sucrose, antioxidants, and anti-caking agents that complicate mass balance and may not meet the definition of an API in a regulatory dossier. The product described here is the unformulated pharmacopoeial cholecalciferol supplied as crystalline powder, oily concentrate, or injection-grade powder/oil. This distinction determines the control strategy: the formulator must qualify blending, oxygen exclusion, light protection, and endotoxin limits rather than relying on a carrier system to provide those functions. Published data for direct substitution of a beadlet with the raw API is limited; any proposed change must be supported by process validation and stability data under the relevant climatic zone conditions.