Calcium Bisglycinate Pharma Grade API is supplied as a white to off-white powder with the stoichiometric formula Ca(C₂H₄NO₂)₂ and molecular mass 188.19 g·mol⁻¹ on the anhydrous basis. The manufacturer’s model system distinguishes three grades: CaBG-PG-DC for direct compression, CaBG-PG-G for wet granulation and roller compaction, and CaBG-PG-I for injectable formulations requiring reduced endotoxin and particulate burden. The product is intended for oral tablet, capsule, granule, powder sachet, aqueous oral liquid, and injectable manufacture after terminal sterilization or aseptic filtration. Elemental calcium is controlled to 18.0–21.0% w/w on the dried basis, reflecting the theoretical 21.3% value for the anhydrous chelate and commercial allowance for residual moisture. Assay of the bisglycinate entity is specified between 98.0% and 102.0% on supplier certificates of analysis.

Compared with inorganic calcium sources, the product differs in dissolution chemistry and processing behavior. Calcium carbonate at 40.0% elemental calcium requires gastric hydrochloric acid for dissolution and releases carbon dioxide on acid contact. Calcium citrate tetrahydrate at 21.1% elemental calcium shows poor aqueous solubility at neutral pH, while calcium gluconate at 9.3% elemental calcium is injectable but imposes a low calcium load per gram. The bisglycinate chelate combines moderate elemental density with water-solubilizing glycine ligands. Below pH 4.0, ligand protonation progressively releases free calcium ions, a shift that is analytically measurable with a calcium ion-selective electrode. Non-pharmaceutical feed or food chelates are not interchangeable with the Pharma Grade API because they may contain sulfate, chloride, or endotoxin residues that exceed injectable limits.

What Limits Direct Compression Tablet Performance in High-Dose Calcium Supplement Lines?

Direct compression is constrained by the physical mass of API required for the elemental dose. At 21.0% elemental calcium, a 500 mg elemental dose requires 2.38 g of calcium bisglycinate, which is generally outside a single swallowable tablet. Direct compression is therefore limited to lower elemental doses or to chewable, dispersible, and large-diameter presentations. The powder has a low bulk density, commonly 0.35–0.55 g/cm³, and flow properties that can be poor if the particle-size distribution is not controlled. High-dose blends with microcrystalline cellulose, croscarmellose sodium, and magnesium stearate segregate when the API D90 exceeds 250 µm and the fine fraction below 75 µm migrates through the hopper. Rotary presses with 10 mm round concave tooling and precompression dwell time not less than 0.03 s are recommended; weight variation must be monitored at intervals not exceeding 15 min and held within ±2.0% RSD. Tablet hardness for chewable presentations is typically 80–120 N, and film-coated swallowable tablets may require 120–180 N. Disintegration is tested under USP <701>, friability under USP <1216>, and dissolution under USP <711> apparatus 2 at 50 rpm paddle speed in 0.1 N hydrochloric acid or water, with product-specific acceptance criteria.

On a production rotary press running at 60–80 rpm, a change in API bulk density from 0.40 g/cm³ to 0.55 g/cm³ can alter fill depth and require feeder shoe adjustment. Overblending with magnesium stearate for more than 5 min at 25 rpm in a bin tumbler may reduce tensile strength by coating the water-soluble chelate surface. A practical blending sequence is to preblend API, filler, and disintegrant, then add the lubricant for the final 3–5 min. If ambient relative humidity exceeds 60%, the API should be pre-dried and the direct-compression suite dehumidified because moisture uptake degrades flow and increases sticking to punch faces. Tableting literature reports ejection force above 2.5 kN for 10 mm flat-faced tooling as a practical signal for lubricant insufficiency, although actual acceptance limits must be established for the specific die and punch configuration. Published data for this specific calcium bisglycinate direct-compression configuration is limited; process capability should therefore be confirmed on the intended production press rather than inferred from other calcium salts.

Granulation becomes necessary when direct-compression mass exceeds the die volume or when batch homogeneity cannot be maintained. Roller compaction is performed with roll pressure 30–70 bar, gap 1.0–2.0 mm, and mill screen 0.8–1.2 mm. The target granule bulk density is 0.50–0.65 g/cm³; ribbon density above 1.35 g/cm³ can produce hard granules that resist compression and reduce tablet tensile strength. Wet granulation with purified water may produce tackiness when residual moisture exceeds 3.5% during high-shear mixing. Fluid-bed drying should maintain product temperature below 45°C, with inlet air temperature 55–65°C and final loss on drying 1.5–2.5%. For sachets, granules are dried to loss on drying ≤2.0% and filled at ≤40% RH to prevent caking. Particle-size distribution is determined by USP <429> or sieve analysis under USP <786>.

For capsule filling, the granule fraction retained between 250 µm and 850 µm is preferred; fines below 150 µm are recompacted. In a size 00 capsule, fill weight combined with microcrystalline cellulose is typically 500–700 mg, limiting elemental calcium to approximately 100–150 mg per capsule depending on granule assay. Capsule filling speed is governed by granule compressibility, and powder bed height must be adjusted in dosator or tamping pin machines to control fill weight variation. Recycling of fines above 30% of total granule mass may reduce tablet tensile strength, but published data for this specific chelate is limited and the effect should be measured for each roller-compacted batch.

When Liquid Oral and Injectable Dosage Forms Require Endotoxin Control

When the API grade CaBG-PG-I is used for aqueous oral liquids or injectable formulations, the manufacturer’s specification adds endotoxin and particulate-control parameters that oral grades do not require. Injectable solutions are prepared by dissolving the API in water for injection to a target elemental calcium concentration of 5–10 mg/mL. pH is adjusted with dilute hydrochloric acid or sodium hydroxide and maintained between 5.5 and 7.0. At pH below 4.0, glycine ligands are protonated and free calcium ion activity increases. Phosphate buffers are not recommended unless precipitation testing demonstrates absence of visible precipitate after 24 h at 2–8°C and 25°C and after terminal sterilization. Published data for calcium bisglycinate in phosphate-buffered injectable systems is limited; compatibility should therefore be established in the final vehicle rather than inferred from oral salt behavior.

Endotoxin limits follow USP <85>. For a solution containing 10 mg/mL elemental calcium and a 10 mL single dose, the total elemental calcium dose is 100 mg. Using the pyrogen threshold of 5 EU/kg, a 70 kg adult yields an endotoxin limit of 3.5 EU/mg elemental calcium. Injectable-grade API is often specified tighter, at 0.5 EU/mg API, to provide process capability. Particulate matter after reconstitution is controlled by USP <788>; small-volume injection limits are not more than 6000 particles/container ≥ 10 µm and 600 particles/container ≥ 25 µm, while large-volume injection limits are 25 particles/mL ≥ 10 µm and 3 particles/mL ≥ 25 µm. Terminal sterilization by moist heat at 121°C for 15 min may be used if stability studies confirm no assay loss or color formation. Otherwise aseptic filtration through a 0.22 µm sterilizing-grade membrane is required, with a 0.45 µm prefilter used when high solute loading may occlude the final filter. Handling of CaBG-PG-I should occur in a controlled area meeting ISO 14644-1 Class 8 or better, with product-contact operations in isolator or laminar flow.

Oral multi-dose liquids require preservative efficacy testing under USP <51>; sodium benzoate or potassium sorbate may be evaluated at compendial levels, with compatibility confirmed by assay and pH drift over 6 months at 25°C/60% RH or 40°C/75% RH. Large-volume parenterals are adjusted to 280–320 mOsmol/kg unless a hypertonic formulation is clinically required, with osmolality measured by USP <785>. Solution pH is verified by USP <791>, and the calcium ion activity may be tracked by ion-selective electrode to confirm that the chelate remains intact under the final sterilization and storage conditions.

Specification and Test Method Matrix for CaBG-PG Grades

Because compendial monographs for calcium bisglycinate may not be harmonized across Ph.Eur., USP, and JP, the following representative parameters are drawn from supplier certificates of analysis and should be confirmed against the current monograph or the drug master file. The absence of a harmonized monograph means the release specification is often a combination of general chapters and the manufacturer’s validated analytical methods. Elemental impurities are controlled under ICH Q3D; oral products use the oral permitted daily exposure, while injectable products require the parenteral permitted exposure. For an oral calcium product with a daily API dose of 2.0 g, the permitted concentration for lead may be calculated from the oral permitted daily exposure; the supplier should provide batch data for cadmium, lead, arsenic, and mercury by USP <233> or a validated inductively coupled plasma mass spectrometry method. Residual solvents are generally limited to Class 3 compounds under USP <467>; if isopropanol is used in purification, its limit must align with USP <467>.

Changeover between oral and injectable grades requires line clearance and verification of residual product, because endotoxin and particulate matter limits differ by orders of magnitude. A shared granulator cannot be used for injectable-grade material after an oral batch unless the contact surfaces are cleaned and endotoxin recovery is verified by rinse sampling with acceptance limits tied to USP <85> and the maximum injectable dose. In warehouses, CaBG-PG-I is stored in double polyethylene-lined fiber drums at 15–25°C and relative humidity not exceeding 40%; opened containers should be reclosed immediately and retested for moisture after 30 days if not fully consumed. These operational boundaries define the practical use envelope for the API across tablet, capsule, granule, oral liquid, and injectable manufacturing.