Direct compression of spray-dried bovine bile extract on high-speed rotary tablet presses is constrained by hygroscopicity and adhesive behaviour of bile acid-rich fractions under compression heat, especially when ambient relative humidity exceeds 60%. Standardised extract complying with the USP Ox Bile Extract monograph—not less than 45.0% total bile acids calculated as cholic acid and loss on drying not more than 6.0%—is blended with microcrystalline cellulose (25–45% w/w), dibasic calcium phosphate dihydrate (15–25% w/w), croscarmellose sodium (2–5% w/w), colloidal silicon dioxide (0.5–2.0% w/w), and magnesium stearate (0.5–1.5% w/w). The bile extract fraction is held at 20–35% w/w to prevent punch filming; batches above 35% w/w exhibit sticking on D-tooling punches at press speeds exceeding 60,000 tablets/h. Blending in a bin blender at 10–20 rpm for 15–25 min is followed by compression at 8–18 kN main compaction force, pre-compression at 1–3 kN, tablet breaking force of 49–118 N (5–12 kp), and friability below 0.8% determined by USP <1216>. Content uniformity is assessed against USP <905>, and uncoated tablet disintegration in water at 37°C is not more than 30 min per USP <701>. Press rooms are maintained at 25°C and 35% RH because cores absorbing moisture above 4.0% w/w laminate during subsequent film coating. Terminal dosage forms include immediate-release oral tablets, film-coated oral tablets, and sub-coated cores for later enteric polymer application.

What Limits Encapsulation Speed When Bile Acid Granules Are Roller-Compacted?

Roller compaction is selected for bovine bile extract intended for capsule filling when the API fraction exceeds 30% w/w and direct compression flow becomes unacceptable due to poor bulk density and segregation. The dry granulation formula contains bovine bile extract at 30–50% w/w, microcrystalline cellulose 20–35% w/w, pregelatinised starch 10–20% w/w, crospovidone 2–4% w/w, and sodium stearyl fumarate 1–2% w/w. Granulation is performed on a roller compactor with hydraulic roll pressure 40–80 bar, roll speed 4–10 rpm, side sealing of the compaction zone, and milling through a 0.8–1.4 mm screen; ribbon density is controlled to 1.10–1.35 g/cm³. Encapsulation on dosator-type machines requires granule bulk density 0.55–0.75 g/mL, Carr index below 25%, and residual moisture 1.5–3.5% w/w. Filling speeds above 20,000 capsules/h on low-fill-weight capsules of 250–400 mg cause powder bridging at the dosing nozzle and unacceptable weight variation under high static charge. Hard gelatin shell moisture is maintained at 13–16%; HPMC shell moisture is maintained at 4–7% to limit embrittlement at 25°C/35% RH filling conditions. Dissolution testing per USP <711> with apparatus 2 at 50 rpm in pH 6.8 phosphate buffer is applied to confirm bile acid release; disintegration is not more than 15 min per USP <701>. Residual solvents and elemental impurities are controlled under USP <467> and ICH Q3D. Terminal dosage forms include hard gelatin capsules, HPMC vegetarian capsules, and capsules containing roller-compacted granules for enteric coating after filling.

Fluid-Bed Spray Granulation of Bile Acid-Rich Fractions

Wet granulation is used when bovine bile extract must be formulated into dispersible oral granules or unit-dose sachet powders with acceptable reconstitution behaviour. A hydroalcoholic binder of purified water and ethanol (70:30 v/v) containing polyvinylpyrrolidone K30 at 3–5% of dry granule mass is sprayed onto a substrate composed of lactose monohydrate and microcrystalline cellulose; the bile extract solids are dissolved or suspended to a level of 10–25% w/w of final granule mass. Top-spray fluid-bed equipment is operated with inlet air temperature 55–65°C, atomising air pressure 1.5–2.5 bar, and spray rate 12–25 g/min per kg substrate. The granulation endpoint is controlled by mean particle size 180–800 µm and loss on drying 1.5–3.0% w/w; residual moisture above 3.0% causes bed collapse and below 1.5% yields a fines fraction that segregates during sachet filling. Particle size distribution is verified by analytical sieving per USP <786>, and residual ethanol is limited by USP <467>. Effervescent variants are buffered with citric acid and sodium bicarbonate, requiring granule drying below 1.5% w/w to prevent premature reaction. Terminal dosage forms include oral granules in unit-dose sachets, flavoured dispersible granules, and enteric-coated granules retained for duodenal release.

Because bile acid salts remain soluble above pH 6.5 but precipitate in the fasting stomach at pH 1.0–3.5, multiparticulate enteric coating is required to prevent gastric aggregation and dose failure. Cores are prepared as microcrystalline cellulose spheres layered with bovine bile extract at 40–60% w/w of core weight and HPMC 5–8% w/w as binder; the drug layering is performed in a Wurster fluid bed at product temperature 30–35°C and spray rate 8–15 g/min/kg. A subcoat of HPMC 2–3% w/w is applied to separate bile acid salts from the enteric polymer and prevent acid-catalysed interaction. Enteric coating with Eudragit L30 D-55 or equivalent methacrylic acid-ethyl acrylate copolymer is applied to 8–12% w/w polymer solids, with triethyl citrate plasticiser at 10–20% of polymer solids and talc at 15–25% of polymer solids. Curing at 40°C and 50% RH for 24 h completes film coalescence and reduces tack during capsule filling. Dissolution testing per USP <711> uses acid stage 0.1 M HCl for 2 h with no more than 10% release, followed by pH 6.8 phosphate buffer where release exceeds 80% within 45 min. Terminal dosage forms include enteric-coated pellets filled into hard capsules, enteric-coated tablets, and enteric-coated granule sachets.

Sodium Deoxycholate Injection, Where pH Drift Determines Yield

Bovine bile fractionation routes that isolate deoxycholic acid monohydrate support a sterile injectable finished product at 10 mg/mL deoxycholic acid in water for injection. The formulation ratio is fixed at 10 mg/mL; higher concentrations increase micellar turbidity and filtration resistance, while lower concentrations require larger injection volumes. Sodium hydroxide is used as pH adjuster to a target pH of 8.3; pH below 7.8 precipitates free acid crystals and pH above 9.0 causes gelation. Dissolution is conducted in water for injection at 20–25°C under nitrogen sparging, with incremental sodium hydroxide addition to avoid pH overshoot above 9.0. Aseptic filtration through 0.22 µm PVDF membranes is performed in a Grade A/RABS line; filling into Type I borosilicate glass vials with chlorobutyl stoppers is followed by visual inspection per USP <1> and visible particulate control per USP <790>. Bacterial endotoxin testing per USP <85> and sterility testing per USP <71> are release criteria; manufacturing complies with FDA 21 CFR 211 and EU GMP Annex 1. Terminal dosage form is a sterile injectable solution administered subcutaneously for adipolysis.

When Micronised Cholic Acid From Bovine Bile Challenges Content Uniformity In Low-Fill Capsules

Cholic acid obtained by saponification, crystallisation, and purification of bovine bile is formulated into capsules in 50 mg and 250 mg strengths for bile acid replacement therapy. The API fraction is dependent on capsule strength: a 50 mg capsule with fill weight 150–200 mg contains 25–33% w/w cholic acid, while a 250 mg capsule with fill weight 400–500 mg contains 50–62.5% w/w cholic acid. Excipients include lactose monohydrate 30–50% w/w, microcrystalline cellulose 20–40% w/w, sodium starch glycolate 2–5% w/w, and magnesium stearate 0.5–1.5% w/w. Jet milling reduces particle size to D90 below 20 µm, which is critical for blend uniformity and dissolution of the low-strength capsule. Blending is performed in a V-blender at 15–20 rpm for 20–30 min, with fill weight verified at intervals of 10–15 min during capsule filling. Content uniformity follows USP <905>; dissolution testing per USP <711> and disintegration per USP <701> are applied to release. Residual solvents and elemental impurities are controlled under ICH Q3C and ICH Q3D. Terminal dosage forms include cholic acid capsules in 50 mg and 250 mg strengths for bile acid synthesis disorders and related oral replacement indications.