Calcium Lactate Pentahydrate USP/BP/EP/JP/CHP Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable is a multi-compendial calcium salt that can be referenced against the separate monograph requirements of the United States Pharmacopeia, British Pharmacopoeia, European Pharmacopoeia, Japanese Pharmacopoeia, and Chinese Pharmacopoeia. The product is supplied as a white to off-white crystalline powder or granular solid with the molecular formula C₆H₁₀CaO₆·5H₂O, molecular weight 308.30 g/mol, CAS registry number 5743-47-5, and a theoretical calcium ion content of 13.0 wt% on the pentahydrate basis. The designation identifies the API and its compendial compliance scope rather than a specific commercial product model. Release documentation normally covers appearance, identification, assay, water content, chloride, sulfate, magnesium and alkali salts, heavy metals, arsenic, and microbial limits according to the current monograph version. Because calcium lactate pentahydrate is manufactured under good manufacturing practice aligned with 21 CFR 211, the material is supported by a certificate of analysis, batch traceability, and stability data generated according to ICH Q1A principles.

Assay and water content require specific attention because the pentahydrate stoichiometry determines the active strength. The theoretical hydrate water fraction is 29.2 wt%. Pharmacopoeial monographs typically express assay on the dried or anhydrous basis to avoid hydration-state drift; the result is commonly controlled within 98.0%–102.0% of the labeled calcium lactate content, but the exact limit must be read from the monograph in force at the time of batch release. Elemental impurities are controlled under ICH Q3D; residual solvent testing follows ICH Q3C when organic solvents are used in final crystallization or wetting steps. The API alone is not a sterile product. Injectable dosage forms require aseptic processing or terminal sterilization, bacterial endotoxin control, particulate matter control, and finished-product sterility assurance; oral-grade certificates of analysis do not automatically satisfy these parenteral requirements.

What Does Hydrate Stoichiometry Mean for Aqueous Processing and Granule Drying?

The pentahydrate form is used in oral solid dosage manufacturing because the bound water influences moisture balance in wet granulation and direct compression. In aqueous granulation, calcium lactate pentahydrate dissolves partially in the granulating fluid, forming a calcium lactate solution that can act as a binder. The granulation endpoint is therefore sensitive to water addition; excess water produces over-wetting, wide granule size distribution, and cycle failure in high-shear granulation. Production-scale high-shear granulators with a bowl volume of 150 L, impeller speed 150 rpm, and chopper speed 1500 rpm are widely used for this material class, but the endpoint should be established by impeller power draw and wet-mass consistency rather than fixed time. Drying must not remove the water of hydration under uncontrolled thermal conditions. Published data for the exact dehydration onset of this specific product under dynamic drying conditions is limited; therefore, fluid-bed drying inlet air temperature is commonly kept at 40 °C to 50 °C, and water content is monitored by Karl Fischer titration according to USP <921> or Ph. Eur. 2.5.12 rather than by infrared balance alone.

Direct-compression grades require defined particle size distribution and flow behavior. A common starting specification may describe d₉₀ ≤ 250 µm, d₅₀ 100–150 µm, and Hausner ratio ≤ 1.35, but these values are formulation-dependent and must be confirmed on the target rotary tablet press. Magnesium stearate at 0.5 wt% provides adequate lubrication for many formulations; amounts above 1.0 wt% can extend disintegration time because the hydrophobic lubricant film controls water penetration into a soluble matrix. Tablet hardness of 60–80 N on a 10 mm round standard concave tool is a practical starting range, but the final hardness must be selected against friability, disintegration, and dissolution results rather than as an isolated value.

For hard gelatin capsules, the API or granulated blend should be controlled to d₉₀ ≤ 180 µm to avoid flow defects in automatic capsule filling machines. Tamping pin settings and fill weight are adjusted to the bulk density of the calcium lactate blend. If the supplied powder contains a high proportion of fine particles below 45 µm, flow through a dosator nozzle may be inconsistent, and slugging or roll compaction may be required before encapsulation.

A separate injectable-grade control strategy is required when calcium lactate pentahydrate is used in parenteral solutions because oral-grade release testing does not automatically cover bacterial endotoxin, sterility, or particulate matter at 10 µm and 25 µm. Calcium lactate pentahydrate is sufficiently water-soluble for liquid oral and injectable formulation use, but phosphate, sulfate, and carbonate admixtures present a precipitation hazard because calcium salts of these anions have low solubility. A compatibility protocol should include pH, visual appearance, calcium ion concentration, and particle sizing after 24 h and 48 h at 25 °C and 2–8 °C. The pH of a dilute aqueous solution is usually neutral to slightly alkaline, typically 6.0–8.0, which permits formulation with weak-acid buffers but not with high-carbonate buffers if visible precipitation or gas evolution is to be avoided. Published compatibility data for calcium lactate in injectable admixtures is more limited than for calcium gluconate; therefore, each finished injectable formulation should be validated for the intended container closure system and terminal sterilization cycle.

Comparison Against Anhydrous and Alternative Calcium Sources

Differences between calcium lactate pentahydrate and anhydrous calcium lactate are primarily water content, calcium assay on an as-is basis, and handling behavior. The anhydrous form has a molecular weight of 218.22 g/mol and a calcium content of 18.4 wt%, but it can absorb moisture and convert to the pentahydrate under humid storage. The pentahydrate has a calcium content of 13.0 wt% as-is; when the master formula calculates elemental calcium, the form must be stated explicitly. Compared with calcium carbonate, calcium lactate pentahydrate has a much lower calcium content per gram and a more neutral pH, but it dissolves more readily in water and does not generate carbon dioxide upon acid neutralization. Compared with calcium gluconate monohydrate, calcium lactate pentahydrate supplies more elemental calcium per gram and is used in oral solid and liquid preparations; however, calcium gluconate is more commonly referenced in injectable admixtures because of extensive compatibility data. The choice is therefore based on elemental calcium load, pH, anion tolerance, and compendial acceptance in the target region.

If Calcium Loading Forces a Direct-Compression Formulation Outside Its Flow Window

When the elemental calcium dose exceeds approximately 500 mg per tablet, the formulation may require more than 50 wt% of calcium lactate pentahydrate. At this loading, direct compression can fail because the API particle size distribution and bulk density cannot support die filling uniformity. In such cases, wet granulation or roll compaction is used. For roll compaction, feed screw speed, roll pressure, and roll gap must be balanced; a starting roll pressure of 4–6 kN/cm is commonly reported for calcium salt granulations, but this specific pentahydrate may require lower or higher pressure depending on particle size, moisture, and preblended excipients. The compacted ribbons are screened through a 1.0 mm mesh and blended with crospovidone at 2.0 wt% and magnesium stearate at 0.5 wt% before compression. Dissolution acceptance testing uses USP <711> apparatus II at 50 rpm in 900 mL of 0.1 M hydrochloric acid for immediate-release tablets. If dissolution falls below the limit, the wet granulation binder level or disintegrant concentration may be adjusted. Uniformity of dosage units is measured by USP <905>, and weight, hardness, thickness, and friability are monitored throughout the compression run.

Batch-to-batch variance in particle size from crystallization can shift tablet weight and hardness. A multi-compendial API that meets assay and impurity limits is not necessarily optimized for direct compression; a specified particle size distribution, bulk density, and flowability should be procured when the product is intended for high-speed rotary tablet presses. If the API is milled to improve flow, the milling step must be validated to avoid excessive fines that reduce bulk density and increase dust exposure. For capsule filling, granulation or slugging may be required before filling to achieve consistent fill weight and avoid segregation of the API from the diluent.

Microbiological quality testing for oral solid dosage release should follow USP <61> and USP <62> or the corresponding Ph. Eur. chapters. For injectable manufacturing, filling should be performed in an ISO 14644-1 Class 5 controlled environment, and the finished product must meet the sterility, endotoxin, and particulate limits applicable to the dosage form and route of administration. The API is commonly packed in food-grade polyethylene double liners inside a fiber drum or equivalent container closure to protect against moisture ingress and physical damage.

Pharmacopoeial alignment across USP, BP, EP, JP, and CHP is not identical in monograph layout, so a single certificate of analysis may require supplementary jurisdiction-specific testing if monograph limits differ. The release program should include identification by infrared absorption, assay by titrimetry or complexometric titration, water determination by USP <921>, impurity screening where specified, and residue on ignition. Differences from non-pharmacopoeial calcium lactate include lower heavy metal and microbial limits, full batch traceability, and suitability for drug-product regulatory filings. The material is not interchangeable with anhydrous calcium lactate on a weight basis without correction for the hydrate water content and calcium assay.