In direct-compression manufacture of marbofloxacin canine tablets, the drug substance is loaded at 2.5%–18.0% w/w across the 5 mg, 20 mg, and 80 mg core strengths, with a 450 mg core containing 80 mg marbofloxacin receiving 17.8% w/w active pharmaceutical ingredient. The dry blend contains microcrystalline cellulose 101 and mannitol SD 200 as compactable fillers, crospovidone at 2.0%–4.0% w/w as disintegrant, colloidal silicon dioxide at 0.5%–1.0% w/w, and sodium stearyl fumarate at 0.5%–1.5% w/w; magnesium stearate is deliberately avoided because divalent magnesium can coordinate with the fluoroquinolone keto-acid moiety and reduce dissolution. Marbofloxacin is milled or sieved through a 500 µm sieve when D90 exceeds 250 µm, then blended in a bin blender at 12 rpm for 20 min. Compression is performed on a rotary tablet press at main compression force 8–20 kN and precompression 3–5 kN; core hardness is maintained at 80–150 N and friability below 1.0%. Aqueous film coating is applied only after core tensile strength exceeds 1.5 MPa and coating weight gain reaches 2.5%–3.5% w/w; the coating provides light protection and swallowability. Release and stability testing follows Ph. Eur. 2.9.40 and USP <905> for uniformity of dosage units, Ph. Eur. 2.9.3 and USP <711> for dissolution, residual solvent levels are controlled under VICH GL18, and impurity profiling follows VICH GL11. Finished units are biconvex, scored, film-coated tablets in 5 mg, 20 mg, and 80 mg strengths for oral administration to dogs.

Why Do Low-Dose Feline Tablets Require Granulation Before Compression?

At the 5 mg feline strength, direct compression with a 1.5%–3.0% w/w API load creates a segregation risk because marbofloxacin particle size distribution and bulk density differ from those of direct-compression fillers. A wet-granulated intermediate is therefore manufactured: marbofloxacin is blended with microcrystalline cellulose 102, mannitol 25, and pregelatinized starch, then granulated in a high-shear mixer using povidone K30 at 5% w/w solids dissolved in purified water:absolute ethanol 50:50 v/v. Because the granulation solvent contains ethanol, the high-shear mixer is rated for flammable solvent handling and operated with nitrogen inerting. The wet mass is discharged through a 1.5 mm screen, dried in a fluid-bed dryer at inlet temperature 60 °C ± 5 °C and product temperature 38–42 °C, and milled through an 800 µm screen. Loss on drying is controlled to 1.5%–2.5% w/w; lower moisture improves blend robustness but increases static charging during compression. The dried granulate is lubricated with sodium stearyl fumarate at 0.75% w/w and compressed into 5 mg and 20 mg scored feline tablets at 6–12 kN. Release testing includes Ph. Eur. 2.9.6 for content uniformity of single-dose preparations, Ph. Eur. 2.9.40 for dosage unit uniformity, and dissolution per Ph. Eur. 2.9.3; stability protocols follow VICH GL3. Finished units are film-coated with low moisture-permeability coating and packed in aluminium-aluminium blister cavities.

Hard Gelatin Capsule Fill Parameters for Dose Titration Presentations

Marbofloxacin capsules are produced when dose-strength intervals outside the marketed tablet range are required for tapering or renal-function-adjusted regimens. The encapsulated blend is formulated with marbofloxacin at 10%–25% w/w, mannitol, pregelatinized starch 1500, colloidal silicon dioxide 0.5% w/w, and sodium stearyl fumarate 1.0% w/w; calcium carbonate and other cation-rich fillers are excluded because fluoroquinolone-chelate formation can lower in vitro release. The blend is dry-compacted on a roller compactor at roll pressure 8–12 kN/cm and gap 1.2–2.0 mm, then milled through a 1.0 mm screen to produce a granulate with bulk density 0.55–0.75 g/cm³. Capsule filling is performed on a dosator or tamping-pin machine into size 3 and size 4 hard gelatin shells under 25%–40% RH; lower humidity causes shell brittleness and higher humidity softens the shell and accelerates API surface film formation. Fill weight is monitored by in-process check weighing at ±3% of target. Release testing uses Ph. Eur. 2.9.40, USP <905>, and dissolution per USP <711> with pH 4.0 acetate buffer; residual solvent limits follow VICH GL18. Finished products are size 3 and size 4 hard gelatin capsules containing 10 mg, 20 mg, or 40 mg marbofloxacin for oral dose titration.

When Granules Are Filled Into Unit-Dose Sachets for Oral Suspension Reconstitution

Dry granulation is used for marbofloxacin oral suspension granules because residual moisture above 3.0% w/w during storage accelerates hydrolytic degradation and reduces sachet content uniformity. The formula carries marbofloxacin at 2.0%–8.0% w/w in a mannitol-based matrix with xanthan gum at 0.3%–0.8% w/w as suspending agent, citric acid and sodium citrate to achieve reconstituted pH 4.2–4.8, and colloidal silicon dioxide as glidant. The drug and excipients are blended in a twin-shell blender and compacted by roller compaction at 6–10 kN/cm; ribbons are milled through a 500 µm screen to yield granulate with particle size 180–500 µm. The granulate is filled into aluminium-foil laminate sachets at 250 mg, 500 mg, and 1000 mg fill weights, with net content uniformity controlled to ±5% of label claim. After reconstitution in potable water to 20 mg/mL, the suspension is used immediately or within the validated in-use hold time; hard water containing calcium or magnesium above 200 mg/L as CaCO₃ is discouraged because cation chelation can reduce dissolved drug availability. Release and stability testing follows Ph. Eur. 2.9.3 for dissolution, Ph. Eur. 2.9.40 for dose uniformity, VICH GL3 for storage stability, and VICH GL18 for residual solvents. Terminal finished formats are unit-dose sachets of granules for oral suspension, labelled to produce 20 mg/mL after reconstitution.

Injectable Aqueous Solution Sterilisation and Fill-Finish Boundaries for Food-Producing Species

Marbofloxacin injectable solution for cattle and swine is formulated at 100 mg/mL, equivalent to 10% w/v active drug substance, in water for injection. The API is charged into WFI at 35–45 °C under a nitrogen purge, and pH is adjusted with hydrochloric acid to 4.0–4.8; sodium hydroxide may be used for back-titration if the pH falls below the lower limit. The solution is cooled to 20–25 °C before filtration through two 0.22 µm sterilising-grade PVDF cartridges in series. Terminal sterilisation is performed at 121 °C for 15 min with an F₀ of not less than 12 min; alternative aseptic processing is used only when terminal sterilisation is demonstrated to degrade marbofloxacin or alter container-closure integrity. Production equipment consists of 316L stainless steel mixing and storage vessels with clean-in-place and sterilise-in-place cycles, and fill-finish occurs under ISO 14644-1 class 5 grade A laminar flow. Filled containers are 100 mL, 250 mL, and 500 mL Type I glass vials with elastomeric closures; for multi-dose presentations, closure integrity and needle reseal testing are added to release. Release testing includes Ph. Eur. 2.6.1 for sterility, Ph. Eur. 2.6.14 for bacterial endotoxins, Ph. Eur. 2.9.19 for sub-visible particles, and VICH GL18 for residual solvents. The finished vials are intended for subcutaneous or intramuscular administration to cattle and pigs.

The principal process conflict in this presentation is the choice between terminal steam sterilisation and aseptic filling. If thermal stability runs at 121 °C show pH drift above 0.2 pH units or sub-visible particle increases beyond Ph. Eur. 2.9.19 limits, aseptic processing is substituted and the sterilisation hold time is minimised. Dissolved oxygen is controlled below 0.1 mg/L by nitrogen sparging before sterilisation, and headspace oxygen is maintained below 2% v/v after capping. If the formulation includes a preservative for multi-dose vials, benzyl alcohol is assessed for compatibility with the rubber stopper and for tissue residue implications in food-producing species; where withdrawal period data are not available for preserved forms, single-use containers are preferred. Cleaning validation follows EudraLex Volume 4 Part I Chapter 5 with residue limits calculated from the lowest oral or injectable daily dose. The process is not transferred to open tank filling without grade A protection because the terminal-filtered solution is exposed briefly during filling and must re-enter a closed path immediately after hopper accumulation.

When the injectable route is scaled to companion animal presentations, marbofloxacin is formulated at 20 mg/mL (2% w/v) in water for injection, pH-adjusted to 4.0–4.8 with hydrochloric acid. The lower API concentration permits full dissolution at 20–25 °C without organic cosolvents, but the solution remains sensitive to photolytic discolouration and is therefore filled into amber Type I glass or covered by an opaque secondary overwrap. Bulk solution is passed through 0.22 µm PVDF filters and filled aseptically into 10 mL, 20 mL, and 50 mL multi-dose vials under ISO 14644-1 class 5 conditions; terminal sterilisation may be applied only when container-closure studies show no stopper deformation and pH drift below ±0.2 pH units. Release specifications include Ph. Eur. 2.6.1, Ph. Eur. 2.6.14 with an endotoxin limit below 0.5 EU/mg, Ph. Eur. 2.9.19, and VICH GL18. Finished units are 10 mL, 20 mL, and 50 mL vials or ampoules containing 20 mg/mL marbofloxacin for subcutaneous or intramuscular administration to cats and dogs.