Lasalocid sodium veterinary-grade API, identified by CAS 25999-31-9 and molecular formula C34H53NaO8 with a molecular weight of 612.77 g/mol, is the sodium salt of the polyether ionophore lasalocid A obtained from Streptomyces lasaliensis fermentation. The dried substance is a white to off-white crystalline powder with low aqueous solubility and broader solubility in methanol, ethanol, acetone, and chlorinated solvents. The veterinary-grade designation means the material is controlled against a recognized pharmacopoeial monograph such as the current USP–NF or Ph. Eur. Lasalocid Sodium for veterinary use, or against an authorized veterinary medicinal product active substance master file. Release controls cover identity, chromatographic assay, related fermentation-derived polyethers, residual solvent profile, elemental impurities, loss on drying, and particle-size distribution. The API is intended for downstream manufacture of medicated premixes, oral powders, granules, tablets, capsules, and non-aqueous solutions or suspensions. Injectable use is not a routine route for this molecule; where a solution is prepared for regulatory pilot work, formulation must address the ionophore’s narrow therapeutic margin and poor aqueous solubility.

No universal commercial model code exists for lasalocid sodium veterinary API. The material is identified by CAS number, pharmacopoeial monograph title, and the active substance master file or CEP reference of the manufacturer. Feed-grade products are usually Type A medicated articles containing a fixed concentration such as 10–20% lasalocid sodium on a carrier; the exact Type A concentration is supplier- and registration-specific and must be read from the product label and the applicable 21 CFR 558.261 clearance. The API differs from the diluted Type A article in assay, impurity profile, particle-size distribution, and packaging; users should confirm whether the material is controlled to a pharmacopoeial monograph or to a proprietary feed additive specification.

Under U.S. feed regulations, lasalocid sodium Type A medicated article is cleared under 21 CFR 558.261. For broiler chickens, the Type A article is diluted into complete feed to provide 75–125 g lasalocid sodium per ton of feed for the prevention of coccidiosis caused by Eimeria tenella, E. acervulina, E. maxima, E. necatrix, and E. brunetti. The same medicated article is used in cattle at lower tonnage levels for coccidiosis control and feed efficiency, with exact inclusion rates by production phase specified in the label. Withdrawal periods and species-specific prohibitions are not transferable across ionophores; monensin, salinomycin, and narasin each have distinct approvals and dose ranges. In the European Union, registered feed additive categories use the feed additive code E 763 for lasalocid sodium, but national label conditions and maximum levels must be verified from the current authorization.

The antiparasitic effect is based on ionophore-mediated transport of alkali and alkaline earth cations across biological membranes. Lasalocid sodium forms neutral complexes with monovalent cations and, unlike monensin and salinomycin, also shows significant divalent-cation binding for Ca²⁺ and Mg²⁺. In susceptible Eimeria species, the resulting disruption of ion gradients impairs schizont development and reduces intestinal lesion formation. In ruminants, the same ion-flux activity alters the rumen fermentation pattern and reduces the metabolic cost of coccidiosis and subclinical infection. Published quantitative comparisons of ion selectivity are available from ionophore chemistry literature; release specifications should not be confused with clinical efficacy data.

The release specification is not a single universal list; the following quality-attribute matrix identifies the methods and standard designations typically referenced in a veterinary active substance dossier.

The HPLC assay is generally run with reversed-phase C18 columns and acetonitrile–phosphate buffer mobile phase with detection near 210 nm; laser diffraction particle-size analysis per USP ‹429› is used when the API is marketed as micronized. Residual solvent methods using headspace GC per USP ‹467› typically focus on methanol, ethanol, ethyl acetate, and acetone. Elemental impurities are controlled under USP ‹232›/‹233› for palladium, nickel, chromium, arsenic, cadmium, mercury, and lead. The exact acceptance criteria for related substances, particularly lasalocid homologues and fermentation-related polyethers, are monograph-specific; a typical dossier may limit individual unspecified impurities to 0.10–0.20% and total impurities to 1.0%, but these values are not universal and must be verified from the current certificate of analysis.

What limits the conversion of this API into aqueous injectable solutions?

Lasalocid sodium has very low water solubility and a narrow systemic safety margin, so aqueous injectable products are generally absent from routine veterinary formularies. Published formulation data for this specific configuration is limited. If a non-aqueous injectable solution is developed for a controlled study, vehicles such as glycerol formal, propylene glycol, or ethanol–water mixtures are selected after screening for hemolysis, precipitation upon dilution with plasma, and injection-site tolerance. Sterility assurance should follow USP ‹1› and USP ‹788› for subvisible particulate matter. Terminal sterilization is not automatically suitable for the polyether structure: high-humidity autoclaving or extended gamma irradiation can generate related substances that must be quantified by HPLC. The ionophore’s ability to bind divalent cations in serum makes intravenous administration particularly hazardous; any injectable use is a high-risk formulation activity rather than a standard product claim.

Powder, granule, and premix manufacturing routes

Low-dose blending is the principal manufacturing route. Lasalocid sodium Type A medicated article is prepared by diluting the API onto a carrier such as rice hulls, ground corn, or calcium carbonate; the active concentration is commonly 10–20% w/w but is fixed by the registration file. Stepwise geometric dilution in a horizontal ribbon blender or V-blender equipped with an intensifier bar is used to reach Type B/C feed or supplement concentrations. For granulated premixes, high-shear wet granulation followed by fluid-bed drying is preferred over direct powder blending when dust suppression, flowability, and metering into automatic feed lines are required. Continuous twin-screw granulation has been evaluated for similar low-dose ionophore formulations; screws with L/D of 25:1 to 40:1 and temperature-controlled barrels below 50°C may be used, but published data for lasalocid sodium in this specific configuration is limited.

Particle-size control is critical because the final broiler feed contains roughly 75–125 ppm active; a micronized or sieved API with a Dv90 below 150–200 µm reduces segregation risk. Blend uniformity is normally evaluated by assaying ten stratified samples and calculating relative standard deviation; regulatory acceptance is often set at RSD ≤ 5.0%, but the final acceptance criterion is application-specific. Equipment surfaces should be dry and free from acidic residues, because the sodium salt can be protonated to the free acid under moisture and low pH, altering solubility and assay. In mineral premixes, copper sulfate and zinc oxide can create an aqueous film that binds the ionophore and reduces assay recovery; published data for this specific configuration is limited. Feed-mill sequencing should include flush runs and dedicated equipment for ionophore products to prevent carryover into equine rations, where ionophore contamination is a recognized toxicity hazard.

When lasalocid sodium is selected over monensin, salinomycin, or narasin

Lasalocid sodium is not a drop-in replacement for other polyether ionophore APIs. Its terminal aromatic side chain and ion-binding cavity confer broader ion selectivity; published structural work shows that lasalocid forms stable neutral complexes with divalent cations such as Ca²⁺ and Mg²⁺, whereas monensin and salinomycin are primarily monovalent-cation ionophores. This difference has practical consequences. The approved target species, feed inclusion ranges, and withdrawal periods differ across ionophore products, and the same grams-per-ton dose must never be assumed. In ruminant feed programs, lasalocid sodium has been used where its divalent-cation affinity offers a different fermentation response, but published comparative efficacy data for this specific configuration is limited to summarized regulatory studies. For poultry coccidiosis control, lasalocid sodium retains activity against Eimeria isolates that may show reduced sensitivity to other ionophores; however, cross-resistance patterns are not fully predictable from pharmacopoeial quality data alone. All ionophores remain toxic to horses and other equines at low contamination levels; feed mills must use dedicated or validated flushed lines to prevent cross-contamination.

Co-administration with tiamulin or related pleuromutilins may potentiate ionophore toxicity in swine and poultry. While the interaction is most consistently documented for monensin, salinomycin, and narasin, the same caution is applied to lasalocid sodium unless the approved label explicitly permits use. Combined use with sulfonamides or macrolides should also be reviewed against species-specific label prohibitions. The product is not for human use and must be handled with containment to avoid inhalation of fine dust and skin contact.

Processing solid oral dosage forms under low-dose blending constraints

Tablet and capsule forms require pharmaceutical-grade excipient compatibility beyond what is necessary for feed premixes. The hydrophobic API can be pre-blended with lactose monohydrate or microcrystalline cellulose and wet-granulated with a binder such as povidone or hypromellose. Direct compression is feasible only if the API particle size is reduced to a Dv50 of 5–20 µm and content uniformity is confirmed per USP ‹905›. Dissolution testing in aqueous media may require surfactant addition such as sodium lauryl sulfate at 0.5–1.0% w/v, because the sodium salt is poorly water soluble. Magnesium stearate should be kept at or below 1.0% w/w to avoid coating the hydrophobic drug and delaying dissolution. Capsule filling on tamping-pin equipment may require colloidal silicon dioxide at 0.2–0.5% w/w to control electrostatic adhesion and improve flow. These ranges are standard low-dose formulation practice, not product-specific release limits; each formulation must be tested for assay, related substances, and dissolution under ICH or VICH stability conditions.

Lasalocid sodium API is stored in tightly closed containers at ambient controlled room temperature, protected from light and moisture. Under relative humidity above 60%, the powder can absorb moisture and become sticky, reducing blend uniformity. Exposure to strong acids, strong oxidizing agents, and certain transition metal ions may promote degradation of the polyether ring system; stainless steel or epoxy-lined equipment is standard. Fine particle dust should be controlled by local exhaust ventilation and high-efficiency particulate filtration, with engineering controls validated by industrial hygiene monitoring. Lasalocid sodium is a fermentation-derived antibiotic and may cause respiratory sensitization in exposed workers.

Oral solutions and suspensions are formulated when liquid dosing is required for poultry drinking water or calf drench. The API is first dissolved in an approved co-solvent such as ethanol or propylene glycol and then dispersed into water under high shear. Because lasalocid sodium is poorly water soluble, the resulting liquid is often a suspension rather than a true solution; thickening agents and wetting agents are required to maintain dose uniformity. The dispersion is tested for sedimentation volume, particle size, and chemical stability. This product form requires preservative efficacy testing if multi-dose use is intended, and it should be packaged in light-resistant containers because the polyether structure may undergo photodegradation. The final formulation must be evaluated for palatability and drinking-water stability under field conditions, because ionophore precipitation can reduce dose intake and undermine coccidiosis control.