The product described is Alpha Ketoanalogue to Valine, Calcium Salt Pharma Grade API, a calcium bis(3-methyl-2-oxobutanoate) supplied under the manufacturer’s grade designation AKV-Ca-PH. The material is intended for incorporation into tablet, capsule, granule, and injectable dosage forms for oral and parenteral administration. The salt is the nitrogen-free α-ketoacid precursor corresponding to L-valine; in multi-ketoanalogue formulations it is typically combined with the calcium salts of α-ketoisocaproate, α-keto-β-methylvalerate, and phenylpyruvate, plus hydroxyacid components in some regional presentations. The anhydrous form has the molecular formula C₁₀H₁₄CaO₆ and a calculated calcium content of 14.8% w/w; the hydrated state must be specified on the certificate of analysis because water content changes the assay basis and the stoichiometric conversion to keto acid equivalents. Grade AKV-Ca-PH is the pharma-grade, low-endotoxin, low-heavy-metal specification used for solid oral dosage and aseptic injectable manufacturing.

What Distinguishes the Calcium Salt of Alpha-Ketoisovaleric Acid in Multi-Ketoanalogue Therapy?

The calcium salt is differentiated from the corresponding free acid and sodium salt by three formulation-critical properties: sodium load, calcium stoichiometry, and hygroscopicity. In patients requiring sodium restriction, the calcium salt contributes no sodium per keto acid equivalent, whereas the sodium salt contributes one mole of sodium per mole of keto acid. The calcium salt delivers one mole of calcium for every two moles of α-ketoisovalerate by charge balance; this must be accounted for in multi-component formulations where the combined calcium intake from all ketoanalogue salts is considered. Compared with α-ketoisovaleric acid, the salt is a crystalline powder with improved solid-state stability and is less corrosive during wet granulation; the free acid is a low-melting, odor-intensive liquid under ambient conditions and is not suitable for direct compression without carrier adsorption. The product also differs from amino acid valine in that it contains no reduced nitrogen; the ketoacid must be transaminated in vivo to generate valine, which is the basis for nitrogen-sparing regimens but imposes a requirement that dietary amino acid adequacy be maintained.

Pharmacopoeial alignment for the pharma-grade calcium salt is maintained through a monographed panel of release tests. The material is a white to off-white crystalline powder; identification is confirmed by infrared absorption spectrum matching and by a positive calcium test. Assay is reported on the anhydrous basis using reverse-phase HPLC with UV detection after derivatization with 2,4-dinitrophenylhydrazine; the method is validated according to ICH Q2(R1) for specificity, linearity, accuracy, precision, and range. The acceptance criterion for assay is typically 98.0–102.0% w/w. Loss on drying is controlled at ≤1.0% by USP <731> or water content by Karl Fischer titration per USP <921> Method Ic. Related substances are limited to single impurity ≤0.50% and total impurities ≤1.00%. Elemental impurities are controlled under ICH Q3D Category 1 and 2A limits using USP <232>/<233>; residual solvents are tested by headspace gas chromatography according to USP <467> and ICH Q3C. For oral solid dosage, particle size is specified as D90 ≤150 µm by laser diffraction per USP <429> to support blend uniformity and direct compression. Bulk and tapped densities are reported under USP <616> to allow calculation of the Carr index and Hausner ratio. For injectable grade, bacterial endotoxin limits are calculated from the dose equation in USP <85>; a typical parenteral API limit is ≤0.25 EU/mg when the maximum adult bolus permits this threshold. Microbial enumeration is performed under USP <61>/<62> with absence of Escherichia coli.

Because the anhydrous salt can form hydrates under ambient humidity, X-ray powder diffraction is used to confirm the crystalline phase. The certificate of analysis reports the XRPD pattern against a reference diffractogram; the major 2θ peaks are recorded but not used for quantitation. This is relevant because different hydration states have different calcium content and different powder compaction behavior. The oral/injectable grade dichotomy is not purely administrative. Parenteral lots are subject to additional bioburden monitoring before filtration and more stringent particulate matter controls; the same crystalline form is used, but the allowable residual solvent profile may be tighter for injectable presentations. ICH Q3C options for Class 1 and Class 2 solvents are applied separately to oral and injectable dose, and the manufacturer should be asked for the injectable-specific residual solvent statement on the certificate of analysis.

Granulation and Compression Parameters in Oral Solid Dosage Manufacturing

In high-shear wet granulation, the API is blended with other ketoanalogue calcium salts, microcrystalline cellulose, crospovidone, and povidone binder solution; purified water is sprayed at a binder addition rate of 0.2–0.5 kg/min for a 600 L vertical granulator. The wet mass is milled through a 4.0 mm screen and dried in a fluid-bed dryer to a target loss-on-drying of ≤1.0% before lubrication with magnesium stearate at 0.5% w/w. Compression on a rotary tablet press operating at 60–80 rpm generally achieves weight variation below 1.0% RSD when the API particle size D90 is ≤150 µm and the final blend bulk density is controlled between 0.45 and 0.65 g/mL. For capsule filling, the blend is filled into size 0 or size 1 hard gelatin or HPMC capsules using an auger or dosator system; the flow of the unmilled API is generally cohesive, so a milled and pre-mixed trituration with lactose monohydrate or mannitol is required before final blending.

For direct compression, a bimodal particle-size distribution with D10 below 10 µm and D50 between 40 and 80 µm improves powder flow and compaction; however, the fines fraction below 10 µm can cause sticking on tablet tooling if the blend is over-lubricated or if tablet press humidity exceeds 55% RH. Tooling prepared from S7 steel with hard chrome plating is advised when compression runs exceed 300,000 tablets per die station. For wet granulation, the same fine fraction is beneficial for binder distribution but can increase granule friability after drying. Sieve analysis after 5 minutes on a motorized sieve shaker is used to verify granule size distribution. Powder flow measurements under USP <1174> may be used to set press speed and hopper vibration settings.

Injectable manufacture uses a separate low-endotoxin lot of the same grade. The API is dissolved in Water for Injection at 20–25°C under nitrogen blanketing; the solution pH is adjusted to the registered target with dilute hydrochloric acid or sodium hydroxide only if compatibility data support the final pH. The solution is passed through a 0.22 µm polyethersulfone or PVDF sterilizing-grade membrane filter. Terminal sterilization is not assumed to be compatible with the α-ketoacid structure; forced degradation studies under heat and alkaline pH must be conducted because oxidative decarboxylation and keto acid–amine adduct formation are known degradation routes. Published forced degradation kinetic data for this specific single-salt injectable configuration is limited; therefore the operating limits above are conservative. The compounded solution should not be stored for extended periods unless a formaldehyde-free and oxygen-free container-closure system is validated. Silicon tubing and 316L stainless steel contact surfaces are acceptable, but extractables and leachables should be assessed under USP <1663> and USP <1664> protocols. The injectable solution should be protected from light during processing and filling because the compound absorbs in the ultraviolet region; amber glass or opaque secondary packaging is used. A 0.45 µm prefilter is used if raw solution turbidity exceeds 1 NTU; dissolved oxygen should be kept below 2 mg/L before filling. Filling line setup uses Type I glass vials with chlorobutyl rubber stoppers and aluminum overseals; headspace oxygen should be below 5% after nitrogen flushing. The filling line is monitored for particulate matter per USP <788> and visible particles per USP <790>.

When Substituting Sodium Ketoanalogues or Free Acids in a Formulation, What Changes?

Substitution on a weight-for-weight basis is incorrect because the molecular masses and hydration states differ. The anhydrous calcium salt has a molecular mass of approximately 270.3 g/mol, whereas the sodium salt has a molecular mass of approximately 138.1 g/mol and the free acid approximately 116.1 g/mol. Conversion must be performed on a molar keto acid equivalent basis: one mole of calcium salt supplies two keto acid equivalents, one mole of sodium salt supplies one, and one mole of free acid supplies one. When replacing the sodium salt with the calcium salt, the formulation loses sodium but gains calcium; the theoretical calcium contribution is 14.8% w/w of the calcium salt mass. In multi-ketoanalogue tablets, the total calcium load from all calcium salts must be considered, and the dissolution profile may shift because the calcium salt has lower aqueous solubility than the sodium salt in some conditions. The free acid replacement requires neutralization or adsorption before dry blending because the free acid is not a free-flowing solid.

Incoming API testing under FDA 21 CFR 211.84 should include identity and purity unless a supplier quality agreement reduces redundant testing under ICH Q7. The API is manufactured under Good Manufacturing Practice for active substances as described in ICH Q7. Each batch is released against a certificate of analysis that includes IR, assay, related substances, residual solvents, elemental impurities, loss on drying, particle size, and microbial controls. For injectable grade, the certificate also reports bacterial endotoxin and bioburden. Retained samples are placed in long-term and accelerated stability conditions per ICH Q1A(R2) and monitored at selected time points. Store the API at 2–8°C in closed double polyethylene bags inside fiber drums and protect from light; moisture uptake increases above 60% RH and reduces flow. The API should not be milled under high humidity because milling-induced amorphous surface regions can increase hygroscopicity. Avoid storage with oxidizing agents, strong acids, and primary amines unless a compatibility study is available. Batch-to-batch variance in particle size and loose density should be reviewed before each campaign; the certificate of analysis reports D10, D50, and D90 values because milled lots are not always monomodal. A re-test interval of 24 months is common for the unopened container, but injectable-grade lots may be assigned a shorter retest interval if endotoxin and particulate controls are critical.