| HS Code | 346814 |
| Product Name | Lactic Acid USP/BP/EP/JP/CHP Pharma Grade API |
| Chemical Name | 2-Hydroxypropanoic acid |
| Synonyms | Lactic acid; 2-Hydroxypropionic acid; Milk acid |
| Cas Registry Number | 50-21-5 |
| Einecs Number | 200-018-0 |
| Molecular Formula | C3H6O3 |
| Molecular Weight | 90.08 g/mol |
| Pharmacopeial Grades | USP, BP, EP, JP, CHP |
| Product Grade | Pharma Grade API |
| Dosage Forms | Tablet, Capsule, Granule, Injection |
| Routes Of Administration | Oral, Injectable |
| Physical Appearance | Colorless to slightly yellow, odorless or nearly odorless, syrupy liquid |
| Assay | Typically 85.0%–92.0% w/w depending on pharmacopeia |
| Solubility | Miscible with water and ethanol; soluble in ether |
| Ph | Acidic; approximately 2.0–3.0 in aqueous solution |
| Specific Gravity | About 1.20 at 25°C |
| Density | About 1.20 g/cm³ at 25°C |
| Melting Point | 16.8°C for DL-lactic acid; 53°C for L-lactic acid |
| Boiling Point | 122°C at 15 mmHg; decomposes on heating |
| Stereochemistry | Racemic or L-(+)-lactic acid depending on grade |
| Water Content | Typically 10–15% in 85–90% aqueous solution |
| Identification | Passes pharmacopeial identification tests |
| Storage Conditions | Store in tightly closed containers in a cool, dry place protected from light |
| Packaging | 25 kg, 250 kg, or bulk drums; polyethylene or suitable pharmaceutical containers |
| Shelf Life | Typically 24 months in unopened original packaging |
| Regulatory Status | Pharmaceutical API compliant with USP/BP/EP/JP/CHP |
| Applications | Acidifier, buffering agent, preservative, pharmaceutical aid, and active ingredient in parenteral solutions |
As an accredited Lactic Acid USP/BP/EP/JP/CHP Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
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Wet granulation of oral solid dosage forms with 85.0–90.0% w/w pharmaceutical-grade lactic acid solution is configured as a pH-modifying granulating fluid rather than a dry binder, because the lactic acid monograph material is a hygroscopic liquid at ambient temperature. The acid solution is diluted to 5–20% w/v with purified water and sprayed onto a dry premix in a high-shear mixer-granulator, typically with a bowl volume between 100 L and 600 L. The target addition ratio for pH adjustment falls between 0.1% and 1.5% w/w on dry granulate mass; deviations above 2.0% w/w have been observed to cause granule sticking and inconsistent particle-size distribution because lactic acid is hygroscopic and reduces the glass transition temperature of amorphous binders in the wet mass. In operation, the granulation endpoint is determined by impeller torque or load-cell power consumption; a rise of 8–15% over the dry-mix baseline is used as a reference endpoint when the wet mass is intended for subsequent fluid-bed drying. The diluted lactic acid solution is delivered through a binary nozzle at 0.8–1.4 bar atomisation pressure and at a defined liquid addition rate that is scaled by batch surface area; after wet massing for 60–180 s, the granules are wet-milled through a 4 mm screen and dried in a fluid-bed dryer with inlet air at 55–70°C until residual moisture is ≤2.0% w/w. Terminally, the dried granules are blended with extragranular disintegrant and lubricant and compressed into tablets or filled into hard capsules. Compliance for these terminal dosage forms includes USP <711> dissolution, USP <905> uniformity of dosage units, ICH Q3D elemental impurities, and USP <467> residual solvents; lactic acid solution prepared from purified water does not introduce Class 1 or Class 2 residual solvents at reportable levels. Terminal product types are compressed tablets, capsules containing granulated fill, and single-dose granule sachets for reconstitution.
In parenteral and dialysis fluid manufacturing, lactic acid is added not as a fixed-percentage excipient but as a q.s. acidifier for lactate-buffered systems; the addition ratio is determined by pH titration to 6.0–7.5 for lactated Ringer’s injection and related intravenous fluids. A typical lactate-buffered intravenous solution contains sodium lactate at 28–31 mmol/L; lactic acid is metered into the compounding vessel under low-shear mixing until the temperature-compensated pH probe at 20–25°C reads the target setpoint. Development batches for this configuration generally consume less than 0.5 g/L of lactic acid before final adjustment, but no universal percentage applies because the buffer capacity of the base solution varies with lot-specific sodium lactate alkalinity and headspace carbon dioxide content. The solution is then filtered through 0.22 µm sterilising-grade polyethersulfone or polyvinylidene fluoride membrane cartridges, filled into glass or multilayer polyolefin containers, and terminally sterilised by moist heat; a typical cycle is 121°C for 15 min with an acceptable F0 ≥ 8 for large-volume parenterals. Lactic acid for injectable use must comply with USP <1> Injections, USP <788> particulate matter in injections, USP <790> visible particulates, EP 5.1.1 sterility, and ICH Q3D elemental impurities. Endotoxin content is verified by USP <85>, with the acceptance limit calculated from the maximum bolus dose and the specific monograph requirement. Incompatibilities in injectable systems include precipitation of cationic actives at elevated pH and pH drift during terminal sterilisation; therefore, pH is rechecked after autoclaving and before release. Terminal product types include lactated Ringer’s injection, intravenous infusion solutions with lactate buffer, and peritoneal dialysis fluids in which lactate serves as the alkalising precursor.
Oral solutions and suspensions use lactic acid primarily as a pH-modifying acidulant; the effective addition range is 0.1–2.0% w/v, with the final target pH typically 3.0–4.5 for chemically stabilised acid-stable actives. Lactic acid is monoprotic with a pKa of 3.86 at 25°C; this buffering behaviour is narrower than citric acid and is used when reduced acidulant molar load is required. The acid is prediluted to a 10% w/v stock solution in purified water and added to the aqueous phase before the active pharmaceutical ingredient is introduced; this sequence limits local pH excursions that could hydrolyse acid-labile actives or force colloidal precipitation of suspending agents. Mixing is carried out in a stainless-steel vessel with an anchor or gate stirrer at 20–40 rpm, and the solution is cooled to 15–20°C before the addition of pH-sensitive preservative systems such as sodium benzoate. Preservative efficacy is confirmed by USP <51> antimicrobial effectiveness testing. Terminal liquid products are also tested for microbial limits under USP <61> and USP <62>, and elemental impurities are controlled under ICH Q3D. For suspensions, redispersibility and sedimentation volume are process parameters rather than acidulant properties; lactic acid affects these indirectly by altering zeta potential and flocculation state, and over-acidification below pH 2.5 can destabilise aluminium or magnesium-containing antacid systems. Terminal product types include paediatric oral solutions, reconstitutable dry syrups, oral drops, and preservative-containing elixirs packaged in amber glass or polyethylene terephthalate bottles with child-resistant closures.
Where low residual moisture and narrow granule-size distribution are required, fluidised-bed top-spray granulation is used to deposit 5–15% w/w aqueous lactic acid solution onto a fluidised bed of active and excipients. The granulator is operated with inlet air temperature 50–70°C, product temperature 28–35°C, spray rate 20–60 g/min, and atomising air pressure 1.0–2.0 bar. The addition ratio for this process is 0.2–1.0% w/w on dry granulate mass. Granulation progress is monitored by pressure drop across the bed and by particle-size samples; the target granule size is D50 150–400 µm, with Hausner ratio ≤1.25 before filling. Exceeding 1.5% w/w lactic acid in this process can cause wetting-induced agglomeration, filter blinding in the fluid-bed exhaust, and a shift in granule porosity that increases disintegration time in terminal capsules. Drying is continued until residual moisture is ≤2.0% w/w; after discharge, granules are screened through a 1.0–1.4 mm sieve and blended with extragranular glidant and lubricant. Flow properties are characterised by USP <1174> powder flow testing, and content uniformity of filled capsules or sachets is verified by USP <905>. Terminal product types are sachet and stick-pack granules for reconstitution, capsules with granulated fill, and compressible granule blends for tablets where a low-shear granule structure is required.
Because dialysis-grade lactate buffer concentrates are produced without terminal pH rework after steam sterilisation, lactic acid is introduced before the filtration step as a dilute 10–20% w/v solution under nitrogen blanketing to limit carbon dioxide absorption. Continuous ambulatory peritoneal dialysis and automated peritoneal dialysis solutions use lactate as the alkalising buffer at 35–40 mmol/L; lactic acid serves as the final pH adjuster when sodium lactate alone does not bring the solution into the target pre-sterilisation pH range of 5.0–6.5. Addition is q.s., and development-scale titrations generally consume less than 0.2 g/L depending on the lactate source alkalinity. The terminal fluid is filtered through 0.22 µm sterilising-grade filters and filled into polyvinyl chloride-free multilayer bags that are steam-sterilised in an overpressure autoclave at 121°C for 15 min; after sterilisation the pH is rechecked and must remain within the registered specification. Compliance includes USP <1> Injections, USP <788>, USP <790>, ISO 23500 for dialysis fluids, and ICH Q3D. Terminal product types are continuous ambulatory peritoneal dialysis fluids, automated peritoneal dialysis solutions, and haemodialysis acid concentrates where lactate is deliberately used as a buffer precursor.
Substitution of lactic acid for citric acid in oral granulation is evaluated on the basis of acid equivalents rather than mass percentage because citric acid is triprotic with pKa values at 3.13, 4.76, and 6.40, whereas lactic acid is monoprotic with pKa 3.86. The replacement factor for equivalent pH shift is therefore not 1:1; development work typically begins at a mass ratio of 1.5–2.0 parts of lactic acid solution (85–90% w/w) per part of anhydrous citric acid, followed by pH titration of the granulating fluid. Lactic acid replacement is considered when citric acid promotes unacceptable chelation or when the buffering profile of citric acid masks a desired narrow pH window. In a high-shear granulation process, the granulating fluid is held at pH 3.8–4.2 before spraying; the addition ratio on dry granulate is limited to 0.2–1.0% w/w to avoid the hygroscopicity-related sticking that increases at higher residuals. Granules are dried at 55–65°C to ≤2.0% w/w moisture, milled through a 1.0 mm screen, and compressed with a rotary tablet press using compaction force 8–18 kN. Tablets are tested for disintegration per USP <701> and dissolution per USP <711>; residual solvent compliance follows USP <467>. Published data for this specific acidulant substitution in pH-sensitive oral granulation is limited; process development is normally driven by pH-buffer-capacity titration data generated on the actual active-excipient premix. Terminal product types are pH-sensitive granules, tablets with acid-stable coatings, and capsules where acidulant substitution is intended to reduce acid molar load.
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Lactic Acid USP/BP/EP/JP/CHP Pharma Grade API is a clear, colorless to pale yellow, hygroscopic liquid composed of 2-hydroxypropanoic acid in equilibrium with its self-ester lactyllactic acid and minor oligomeric species. The compendial assay reports total titratable acidity as lactic acid, with the general acceptance range 88.0–92.0% w/w for the neat liquid in current USP-NF, Ph.Eur., BP, JP, and ChP monographs. The molecular formula is CH₃CH(OH)CO₂H, the molecular weight is 90.08 g/mol, and CAS registry numbers are 79-33-4 for L-(+)-lactic acid and 50-21-5 for racemic DL-lactic acid. The product is supplied for use in tablet, capsule, granule, injection, oral, and injectable manufacturing, with the recognition that the neat liquid is not a finished dosage form and must be diluted, neutralized, or processed before administration.
Because lactic acid self-esterifies, the free monomer concentration depends on concentration, temperature, and water activity. At the supplied 88.0–92.0% w/w concentration, the equilibrium mixture contains dimeric and oligomeric esters; dilution with purified water shifts the equilibrium toward monomeric acid. This is a critical processing variable for injectable formulation, where titration before complete hydrolysis can understate the ultimate acid concentration after equilibration. The pKa of lactic acid is 3.86 at 25 °C, placing useful buffer capacity between approximately pH 2.86 and pH 4.86. Solutions for pH adjustment are therefore rationalized using the Henderson-Hasselbalch equation rather than by fixed volume addition.
Multipharmacopoeial control is maintained by superimposing the most restrictive limit from each monograph on a single manufacturing stream. Current monographs specify appearance, solubility, relative density, refractive index, sulfated ash, chloride, sulfate, oxalate, reducing sugar, and related carboxylic acid impurities. The density acceptance range is 1.20–1.21 g/mL at 20 °C, and refractive index is typically 1.425–1.439 at 20 °C for the 88.0–92.0% w/w material. Sulfated ash is controlled by Ph.Eur. 2.4.14 at not more than 0.1%; chloride and sulfate limits are applied as the specific monographs direct, and the related acid profile is confirmed by HPLC or ion chromatography against a compendial reference standard.
| Control parameter | Typical compendial acceptance | Method designation |
|---|---|---|
| Assay as C₃H₆O₃ | 88.0–92.0% w/w | Acid-base titration after hydrolysis |
| Relative density | 1.20–1.21 at 20 °C | USP <841>; Ph.Eur. 2.2.5 |
| Refractive index | 1.425–1.439 at 20 °C | USP <831>; Ph.Eur. 2.2.6 |
| Sulfated ash | ≤ 0.1% | Ph.Eur. 2.4.14; USP <281> |
| Bacterial endotoxins for injectable grade | As agreed, commonly < 0.5 EU/mg | USP <85>; Ph.Eur. 2.6.14 |
The BP and Ph.Eur. monographs for lactic acid are aligned with the European Pharmacopoeia, allowing a single batch release to serve both markets without retesting for core identity and purity parameters. JP and ChP accept the same assay range but may differ in packaging-stability data expectations and regional residual solvent testing requirements. For a product declared as L-(+)-lactic acid, stereochemical identity is critical; the user should confirm the enantiomeric ratio by the method in the requested pharmacopoeia, because racemic DL-lactic acid and L-(+)-lactic acid are not automatically interchangeable in all formulations.
Elemental impurities are controlled under USP <232> and USP <233> or Ph.Eur. 2.4.20 risk-based criteria. Residual solvent testing is conducted under USP <467> or Ph.Eur. 2.4.24; fermentation-derived lactic acid normally shows low levels of ethanol or methanol from purification, but the exact profile must be verified for each manufacturing stream. Microbial enumeration for oral grade follows Ph.Eur. 2.6.12 and 2.6.13 or USP <61> and <62>; injectable-grade material is additionally tested for sterility only after final sterilization or aseptic filling because the raw material is not sterile.
Dispersion of lactic acid into a tablet core is normally performed in the wet-granulation fluid rather than by direct addition to the dry blend. A high-shear mixer or top-spray fluidized-bed granulator is charged with the solid excipients, and the lactic acid–water solution is introduced through a nozzle or peristaltic pump to control addition rate. The use of a solution avoids poorly distributed acid pockets that can hydrolyze moisture-sensitive actives or discolor amine-containing excipients. Published data for a universal addition level is limited because the required quantity depends on the buffering capacity of the active pharmaceutical ingredient, the granulation solvent volume, and the target final tablet pH. Preformulation studies commonly titrate a wet mass or 10% slurry to a defined pH window and then back-calculate the lactic acid charge. At relative humidity above 60%, hygroscopic pickup can increase granule moisture content, reduce flow, and raise ejection force in tablet compression; conditioned rooms with 30–50% RH are used for extended runs.
For capsule products, lactic acid is typically pre-blended with a carrier such as microcrystalline cellulose or colloidal silicon dioxide to reduce localized acidity. Gelatin capsule shells are sensitive to moisture and acidic hygroscopic fills; moisture migration from the fill to the shell can alter shell brittleness. Hydroxypropyl methylcellulose capsules may be selected when formulation pH and humidity cannot be fully controlled. For granules, the acidified granule is dried to a loss-on-drying target in the 1–3% range before compression or encapsulation, but the exact target is product-specific.
In vitro dissolution testing of tablets prepared with lactic acid is typically performed with USP <711> Apparatus II at 50 rpm in 900 mL of 0.1 N hydrochloric acid or compendial buffer. Lactic acid modifies the local pH at the tablet surface during disintegration and can increase the dissolution rate of weakly basic compounds that benefit from acid-mediated wetting; however, the effect is not linear and depends on tablet porosity, binder type, and the pKa of the active. Published dissolution data for a specific lactic acid level in a particular formulation is limited; the level is therefore established by a candidate-formulation design using at least three lactic acid concentrations and a comparator without added acid.
For injectable manufacture, lactic acid is controlled as a low-endotoxin, low-bioburden solution. Endotoxin testing is performed by the limulus amebocyte lysate method of Ph.Eur. 2.6.14 or USP <85>; acceptance limits are based on the final dose and the maximum intended infusion volume, not on the neat solution alone. For a parenteral pH adjuster, a common raw-material limit is < 0.5 EU/mg, but formulators must verify the final product limit using the maximum dose. Particulate matter in the finished parenteral is assessed by USP <788> or Ph.Eur. 2.9.19 after aseptic filtration; the neat lactic acid liquid is not injected because of its viscosity and acidic pH. Sterilizing-grade filters of hydrophilic polyethersulfone or polyvinylidene fluoride are typically qualified by bacterial retention and extractables testing under acidic conditions; nylon and certain membrane filters may show extractable shifts at low pH and are not used without validation.
Terminal sterilization of compounded solutions requires heat-penetration studies because the hydrolysis of lactyllactic acid is time- and temperature-dependent. After dilution to the working concentration, a controlled equilibration period at 20–25 °C is applied before pH adjustment; the exact duration is established by monitoring total acidity until successive titrations differ by less than the validated analytical error. Exceeding the holding time in low-buffered systems can shift pH enough to affect drug solubility or precipitation of sparingly soluble bases.
For injectable pH adjustment, lactic acid is usually added as a 1–10% w/v diluted solution after the active pharmaceutical ingredient is dissolved and cooled, because the acid–base reaction is exothermic. The choice between lactic acid and hydrochloric acid in parenteral pH adjustment is governed by buffer capacity: lactic acid provides a defined pKa and moderate buffer region, while hydrochloric acid does not provide buffer capacity. This difference is important when the final product requires pH stability during storage. The addition rate is controlled by a metering pump and the pH signal is logged at 25 °C; temperature correction is applied because pH electrodes exhibit temperature-dependent slope. Overshoot is corrected with sodium lactate solution rather than sodium hydroxide when the formulation-design buffer ratio must be maintained.
L-(+)-Lactic acid and racemic DL-lactic acid differ in their stereochemical identity and potential biological handling. Mammalian metabolism favors L-lactic acid, and many injectable applications specify L-(+)-lactic acid or the corresponding sodium lactate to avoid unnecessary D-isomer load. D-lactic acid is not metabolized at the same rate and can accumulate in certain clinical conditions; for this reason, a parenteral-grade lactic acid source should identify the enantiomeric ratio in the certificate of analysis. In solid oral forms, the enantiomer has little direct influence on pH modification or tablet hardness, but its origin may affect the impurity profile. Fermentation-derived L-lactic acid may contain residual sugars, peptides, or nucleotides from the microbial source; synthetic racemic material may contain residual degradation products from lactonitrile hydrolysis. The compendial monographs control these impurities, but the impurity fingerprint can vary between manufacturers and should be incorporated into the user's raw-material risk assessment.
Neat lactic acid at 88.0–92.0% w/w has a density above 1.20 g/mL and a dynamic viscosity that is highly temperature-dependent; transfer from drums or totes is typically performed with air-displacement pumps or peristaltic pumps in 316L stainless steel or polypropylene components. Prolonged contact with carbon steel or aluminum is avoided because the acid liberates hydrogen and generates metal lactate residues. Glass-lined equipment and fluoropolymer gaskets are used for long-term storage. Filtration of bulk lactic acid through 0.45 µm or 0.22 µm membrane filters may be required for injectable processing; filter compatibility studies use a 24-hour static soak at 25 °C and 40 °C to measure extractable ions and weight loss. Published data for a specific filter type is limited; qualification is performed with the actual filter lot and the actual dilution.
The α-hydroxy acid group in lactic acid chelates polyvalent metal ions. In parenteral formulations, this chelation can suppress trace-metal-catalyzed oxidation of certain actives, but it can also alter the speciation of electrolyte salts or metal-containing imaging agents. In oral liquid and solid dosage forms, the same property may affect the stability of iron-containing excipients and should be evaluated through forced-degradation studies using final formulation and packaging.
Technical-grade lactic acid is not suitable for pharmaceutical use because the heat-process stream may contain high-boiling oligomers, color bodies, and traces of catalysts; food-grade material, although safe for ingestion, does not routinely meet endotoxin, microbial, particulate, and residual solvent requirements of injectable products. Polymer-grade lactic acid is often a high-purity monomer but may be packaged in containers with processing aids that are not acceptable for pharmaceutical use; it is not released under pharmacopoeial monographs and may lack the compendial certification required for drug product filing. The compendial product differs by the existence of a multipharmacopoeial certificate of analysis, declared enantiomeric composition, and defined limits for water, related carboxylic acids, residue on ignition, and injectable-specific contamination.
Storage recommendations follow compendial general notices and manufacturer stability data: keep containers tightly closed in a cool, dry place, typically below 25 °C; excursions above 40 °C accelerate self-esterification and color formation. Nitrogen or vacuum packaging is not required but reduces oxidative yellowing during long-term storage. Container-closure integrity is verified by dye ingress or helium leak testing as part of the packaging qualification. Once opened, the material is used within a validated working period to limit water uptake; refrigerated storage of partially used containers is not recommended unless the container is resealed under dry conditions and the manufacturer has generated stability data for such hold times.
