Menbutone is supplied to formulation sites as the free acid or the sodium salt; the downstream processing routes below are limited to oral bolus, capsule/tablet, granule/drench, oral paste, and injectable presentations used in veterinary hepatobiliary support. No human medicinal, food, feed additive, or disinfectant application is represented.

When High-Dose Ruminant Oral Boluses Require Menbutone Free Acid to Remain Non-Hygroscopic During Saccharide-Based Granulation

In the production of oral boluses for cattle and sheep, menbutone free acid is dry-blended with a saccharide or polyol carrier before low-moisture granulation because the acid form can be densified without excessive sticking when granulation liquid is applied at 8–12% w/w of the dry blend. A harmonised monograph does not prescribe one addition ratio; for a declared unit containing 1.0 g menbutone in a 5.0 g bolus, the active substance represents 20.0% w/w of the core mass, and higher unit strengths are achieved by adjusting the filler/binder system rather than by increasing granulation liquid. The downstream process uses a high-shear granulator followed by a rotary tablet press, with granule moisture controlled between 2.0% w/w and 4.0% w/w; when facility relative humidity exceeds 60%, the API and excipients are pre-dried and the compression suite is dehumidified to below 45% RH to prevent punch-face adhesion. Compliance is maintained under EU Directive 2001/82/EC as amended and FDA 21 CFR 211 for imported or exported batches; content uniformity is checked according to Ph. Eur. 2.9.40, friability according to Ph. Eur. 2.9.7, and dissolution according to Ph. Eur. 2.9.3 where the registration dossier requires a dissolution specification. Production-scale rotary presses with 12–16 stations and bolus tooling in the range of 16–21 mm diameter are used, and the main manufacturing failure mode is hardness drift in saccharide-based matrices after final drying. Terminal finished product types include round or caplet-shaped oral boluses in aluminium/PVC blisters, polypropylene bottles with induction seals, and single-dose sachets for direct oral administration.

What Terminal Sterilization Limits Apply to Menbutone Sodium Injection at 100 mg/mL Free Acid Equivalent?

Menbutone sodium for injectable solutions is prepared from the free acid or supplied as the sodium salt, and the free acid equivalent is calculated using the molecular masses 208.21 g/mol for menbutone and 230.19 g/mol for the sodium salt, a conversion factor of 1.105. A solution declared as 100 mg/mL menbutone therefore requires 110.5 g/L of menbutone sodium on an anhydrous basis; if the batch certificate shows water or residual solvent content above 0.5% w/w, the weighed mass is corrected against the assay value before dissolution in water for injection at 35–45°C. Sterility and endotoxin compliance are demonstrated after terminal steam sterilisation at 121°C for 15 min under a validated load, with Ph. Eur. 2.6.1 sterility testing, Ph. Eur. 2.6.14 bacterial endotoxin testing, and environmental monitoring according to EU GMP Annex 1 and ISO 14644-1; the filling zone is maintained as Grade A with a Grade B background, and the container-closure system is qualified by dye ingress or vacuum decay according to Ph. Eur. 3.2.9. Published data for menbutone-specific degradation kinetics under autoclave cycles are limited, so the solution pH is maintained at 7.8–8.2 with sodium hydroxide and a nitrogen overlay to suppress oxidative discolouration; the solution is passed through a 0.22 µm sterilising-grade filter before autoclaving, and the maximum hold time between dissolution and sterilisation is controlled at 8 hours to minimise bioburden accumulation. Residual solvents are controlled against VICH GL18 and ICH Q3C, and elemental impurities against ICH Q3D; additional extractables studies from the rubber closure are required because the aqueous sodium salt can extract vulcanisation residues at pH values above 7.5. Terminal finished product types include single-dose or multidose glass vials of 50 mL, 100 mL, and 250 mL with rubber stoppers and aluminium caps, intended for intramuscular or slow intravenous administration in cattle, horses, sheep, and goats.

For companion animal hepatobiliary support capsules, the low aqueous solubility of menbutone free acid makes direct encapsulation without particle size reduction a content-uniformity risk, so the API is air-jet milled or micronised before blending with lactose monohydrate, croscarmellose sodium, and magnesium stearate. Because published formulation data for menbutone capsule fill ratios are limited, the addition ratio is fixed by the approved dossier; a representative fill target for a 100 mg capsule is 15–20% w/w menbutone with disintegrant at 2–4% w/w and lubricant at 0.5–1.0% w/w, while lower strengths are pre-dispersed in lactose at a 1:10 active-to-diluent ratio by geometric dilution. The downstream process includes sieving the micronised API through a 500 µm screen, blending in a bin blender at 60–70% fill volume for 10–15 minutes, and filling into size 3 or size 4 hard gelatin or hydroxypropyl methylcellulose capsules on an automatic capsule filler with tamping pins. In-process controls include uniformity of mass according to Ph. Eur. 2.9.5, content uniformity according to Ph. Eur. 2.9.40, and dissolution according to Ph. Eur. 2.9.3 using a paddle apparatus with pH 6.8 phosphate buffer where the acid is ionised; residual solvents are controlled under VICH GL18 and ICH Q3C, elemental impurities under ICH Q3D, and microbial quality under Ph. Eur. 5.1.4. Terminal finished product types include capsules or tablets in veterinary prescription packs, filled into PVC/aluminium blisters or high-density polyethylene bottles with desiccant, intended for companion animals under veterinary supervision.

Fluid-Bed Granulation of Menbutone Oral Granules for Drench and In-Feed Admixture

High-shear or fluid-bed granulation of menbutone oral granules introduces a particle-size threshold that controls both reconstitution in water and blend uniformity when the product is mixed into a dry feed. The API is dispersed at 15–25% w/w in a mannitol/povidone matrix for oral drench granules; for medicated feed premixes, the active substance is first prepared as a 5.0% w/w premix with lactose or wheat middlings before veterinary-supervised dilution into the final feed, because direct addition of raw API to feed would create content variability beyond the homogeneity limits permitted under EU Regulation 2019/4 for medicated feed. Compliance is linked to EU Directive 2001/82/EC for veterinary medicinal products, Ph. Eur. 5.1.4 for non-sterile oral microbiological quality, ICH Q3D for elemental impurities, and VICH GL18/ICH Q3C for residual solvents from the granulation solvent. The production process uses a top-spray fluid-bed granulator with inlet air temperature 50–60°C, product temperature 28–32°C, and spray rate adjusted to keep the droplet size below 150 µm; the dried granules are passed through a 1.0 mm sieve to remove oversize agglomerates, and the resulting particle-size distribution is measured by sieve analysis according to Ph. Eur. 2.9.12. Batch-to-batch variance on commercial fluid-bed dryers is typically observed in the fine fraction below 150 µm, which segregates during downstream transfer and must be controlled by maintaining final moisture content at 2.0–3.0% w/w; over-dried granule beds generate electrostatic fines, while wet granule beds form hard agglomerates that no longer pass the 1.0 mm screen. Terminal finished product types include single-dose sachets of 10 g or 25 g for oral drench after reconstitution, bulk drums for medicated feed incorporation, and unit-dose cups for calves and foals.

Equine oral paste suspensions containing menbutone free acid are manufactured without water to reduce hydrolytic degradation risk and to maintain suspension rheology, so the API is dispersed in a non-aqueous vehicle composed of medium-chain triglycerides, hydrogenated castor oil, and fine-particle silica suspending agent. The addition ratio for a paste in a multidose calibrated syringe is typically fixed as 20–35% w/w menbutone, with the suspending agent at 2–4% w/w and lecithin at 1–2% w/w; published formulation data for this specific configuration are limited, and the exact ratio is controlled by the approved marketing authorisation, not by a public monograph. The production process includes pre-dispersion of the API through a 250 µm screen, high-shear mixing under vacuum to remove entrained air, and filling into graduated high-density polyethylene syringes with a plunger lock to prevent leakage; viscosity is measured at 20°C with a rotational viscometer and maintained between 30,000 and 80,000 mPa·s to restrain sedimentation during storage, while the API remains suspended rather than dissolved. Compliance for oral non-sterile products follows Ph. Eur. 5.1.4 and EU Directive 2001/82/EC, with uniformity of mass for single-dose preparations checked according to Ph. Eur. 2.9.5 and content uniformity according to Ph. Eur. 2.9.40 where applicable; residual solvents are controlled under VICH GL18 and ICH Q3C, and elemental impurities under ICH Q3D. Terminal finished product types include 30 mL and 60 mL multidose syringes with dose graduations of 2.0 mL, intended for oral administration to horses under veterinary prescription.