Direct compression imposes a D90 ceiling of 250 µm for blend uniformity.

The API is dry-blended for direct compression only after particle-size characterization establishes a D90 below 250 µm, a D50 between 75 µm and 150 µm, and a compressibility index below 25% as described in USP <1174>. Because flow through a gravity-fed rotary tablet press feed frame deteriorates when the powder bulk density falls below 0.40 g/mL, the as-received lot is passed through a 500 µm conical screen mill at 1200 rpm to break agglomerates before weighing. If residual moisture exceeds 2.0% by USP <921> or Ph. Eur. 2.5.12, pre-drying in a fluid-bed dryer at 40°C with an inlet dew point below −20°C is required before blending. Lot-to-lot particle-size shifts above 15% in D50 require re-validation of blend time because the segregation potential in free-flowing systems changes with particle-size span.

The direct-compression frame contains 2.0–10.0% w/w API, 55.0–70.0% w/w microcrystalline cellulose NF, 20.0–35.0% w/w lactose monohydrate NF, 2.0–5.0% w/w croscarmellose sodium NF, 0.5–1.0% w/w colloidal silicon dioxide NF, and 0.5–1.0% w/w magnesium stearate NF. The API is first blended with a portion of microcrystalline cellulose and lactose for 10 min in a 600 L bin blender at 10 rpm. Colloidal silicon dioxide is then added and blended for 5 min; magnesium stearate is added last for 3–5 min. Extended lubrication beyond 5 min reduces tablet tensile strength by hydrophobic surface coating, so the blend holding time after final lubrication is capped at 8 h. In-process blend uniformity is verified by near-infrared spectroscopy at 3 predefined sampling locations with an RSD target below 5.0%.

Tablets are compressed on a rotary tablet press equipped with a force feeder running at 20–40 rpm. Pre-compression force is set at 3–5 kN and main compression at 12–25 kN. Turret speed is held between 30 rpm and 60 rpm depending on punch diameter, with dwell time controlled above 20 ms to avoid capping. Target tablet breaking force is 60–120 N as measured by USP <1217>; friability remains below 0.5% after 100 revolutions per USP <1216>; uncoated tablets disintegrate within 15 min per USP <701>. Weight variation is monitored every 15 min with acceptance limits based on tablet weight and a USP <905> acceptance value not exceeding 15.0.

The terminal finished product is an immediate-release tablet, either uncoated or film-coated, released against USP <711> dissolution with the Q value set by the pharmacopoeial monograph.

Encapsulation of the API at content levels below 5.0% w/w creates a blend uniformity problem that cannot be solved by simple extended mixing. The API is first screened through a 250 µm sieve, then pre-mixed with a portion of lactose monohydrate NF in a high-shear mixer at 100 rpm for 5 min. The pre-mix is passed through a 500 µm screen, and geometric dilution is completed by adding equal portions of the lactose-pregelatinized starch carrier every 10 min. Final blending in a double-cone blender at 15 rpm for 20 min is followed by 2 min lubrication with 0.5–1.5% w/w sodium stearyl fumarate. Total blend time is deliberately limited to 30–40 min because over-blending below 5.0% w/w drug content can induce electrostatic segregation under humidity below 30% RH. Published data for this specific API-lactose premix combination is limited; therefore, the mixing parameters require confirmation by a blend uniformity design of experiments covering mixer loads from 50% to 80% and blend times from 10 min to 40 min.

The final fill formulation contains 0.5–5.0% w/w API, 60.0–75.0% w/w lactose monohydrate, 15.0–30.0% w/w pregelatinized starch, 0.5–1.0% w/w colloidal silicon dioxide, and 0.5–1.5% w/w sodium stearyl fumarate. Filling is performed on a dosator-type capsule machine or a tamping-pin machine with size 0 or 1 hard gelatin capsules. Dosator pins are set to a powder bed height of 12–16 mm, and tamping stations operate at 5–8 mm penetration depth with 10–15 tamping cycles per station. Fill weight is checked gravimetrically every 15 min; mean fill weight variation must stay within ±5.0% for capsules below 300 mg and ±3.0% for capsules above 300 mg as defined by USP <905> and Ph. Eur. 2.9.40. The filling suite is maintained at 35–55% RH and 20–25°C. Below 35% RH, gelatin shells lose moisture and become brittle; above 55% RH, shell softening and powder clumping occur. HPMC capsules may be used when fill humidity must remain below 35% RH.

The finished hard capsules are tested for dissolution per USP <711>, with sink conditions established in 900 mL of dissolution medium at 37°C and paddle speed at 50 rpm. The acceptance criterion is Q ≥ 80% dissolved at 30 min for an immediate-release monolithic fill unless the pharmacopoeial monograph specifies otherwise. Weight sorting, rejection of split or dented shells, and final release follow 21 CFR 211.165. The terminal product is a hard gelatin or HPMC capsule containing an immediate-release powder blend.

When binder viscosity exceeds 400 mPa·s in high-shear granulation

Wet granulation is selected for the API when the direct-compression blend fails to meet USP <1174> flow requirements or when tablet weight variation exceeds 2.0% RSD at press speeds above 50 rpm. A binder solution is prepared by dissolving povidone K30 in purified water at 3.0–5.0% w/w and mixing until the viscosity measured on a Brookfield viscometer reads 200–400 mPa·s at 25°C. If the measured viscosity exceeds 400 mPa·s, the addition rate is reduced to 10 g/min per kg of dry mass or the binder concentration is lowered to 2.0% w/w to avoid localized overwetting and lump formation.

The high-shear granulator is charged with 10.0–25.0% w/w API, 45.0–65.0% w/w lactose monohydrate, 10.0–20.0% w/w microcrystalline cellulose, and 2.0–5.0% w/w croscarmellose sodium. Impeller speed is set to 300–500 rpm and chopper speed to 1500–3000 rpm. Binder solution is sprayed at 10–20 g/min per kg of dry mass through a 1.0 mm nozzle. The granulation end point is identified when impeller torque increases 2.0–5.0 N·m above the dry-mix baseline or when power draw rises 10–15%. Overgranulation beyond the torque plateau produces dense granules that resist disintegration and can increase tablet friability.

The wet mass is discharged through a 6.3 mm screen into a fluid-bed dryer. Inlet air temperature is held at 50–70°C for non-thermolabile API and reduced to 45°C when the API demonstrates degradation above 60°C. Product temperature is maintained at 35–45°C until loss on drying by USP <921> reaches 1.0–2.0%. Dried granules are milled through a cone mill equipped with a 1.0 mm screen at 1500 rpm. The target granule D50 is 150–300 µm, with fines below 75 µm limited to 20% of total mass to avoid segregation during tablet compression. After milling, 0.5–1.0% w/w magnesium stearate is added and blended for 3 min.

Tablet compression uses main compression force between 15 kN and 30 kN. If film coating is required, a 48-inch perforated pan applies an aqueous coating dispersion at 2.0–4.0% w/w weight gain using inlet air 60–80°C and pan speed 4–8 rpm. The finished film-coated tablets are released against USP <905>, USP <711>, and USP <1217>. The terminal product is a high-dose film-coated tablet manufactured by high-shear wet granulation.

Dry granulation is used when the API shows hydrolytic instability or when the wet granulation drying step would require a product temperature below 40°C and an inlet dew point below −30°C. The API is pre-blended with 30.0–50.0% w/w microcrystalline cellulose, 20.0–35.0% w/w anhydrous lactose, and 3.0–5.0% w/w crospovidone. A portion of magnesium stearate, typically 0.25% w/w, is added before compaction to prevent hot-melt adhesion of the powder to the rolls. The mixture is compacted on a roller compactor with knurled rolls at a specific roll force of 4–8 kN/cm, roll speed 5–12 rpm, and gap width 1.0–2.0 mm. Ribbon solid fraction is maintained between 0.55 and 0.70; below 0.55 the compact is friable and generates excessive fines, above 0.70 the API may undergo work hardening that reduces tablet tensile strength.

The ribbons are milled through a 0.8–1.0 mm screen at 1000–1500 rpm to produce granules with D50 180–300 µm. The remaining extragranular lubricant, 0.25–0.5% w/w, is added after milling to avoid hydrophobic surface coverage during compaction. Final blend time is limited to 3–5 min. The finished granulation is compressed at main compression force 15–30 kN to tablets with tensile strength above 1.5 MPa as measured by USP <1217>. If tensile strength falls below 1.5 MPa, up to 10–20% w/w extragranular microcrystalline cellulose is added to restore compactability. Release testing for dry-granulated tablets includes USP <905> dose uniformity, USP <711> dissolution, USP <1216> friability, and ICH Q3D elemental impurity verification using inductively coupled plasma mass spectrometry. The batch record documents ribbon solid fraction at 15 min intervals to demonstrate process consistency. The terminal product is a moisture-stable immediate-release tablet or hard capsule.

Granules intended for reconstituted oral suspension are produced when the API degrades in aqueous vehicle faster than the assigned shelf-life limit of 10% total degradation products. The formulation contains 5.0–20.0% w/w API, 60.0–80.0% w/w sucrose or mannitol, 5.0–10.0% w/w pregelatinized starch, 2.0–5.0% w/w crospovidone, 0.2–0.5% w/w xanthan gum as suspending agent, 0.05–0.1% w/w polysorbate 80, and 0.1–0.2% w/w sodium benzoate if preserved. Dry granulation is conducted at roll force 4–6 kN/cm with a 0.8–1.0 mm milling screen. Wet granulation, when selected, uses povidone K30 at 2.0–5.0% w/w and fluid-bed drying to LOD below 2.0%. The granules are sized through a 1.0 mm screen; granule D50 is 150–300 µm and D90 is below 500 µm to maintain acceptable flow on a sachet form-fill-seal line.

Sachet filling is performed on a vertical form-fill-seal machine at 60–80 sachets/min. Fill weight RSD is controlled below 2.0%, and seal integrity is tested by vacuum leak detection at −40 kPa for 10 s. After reconstitution with purified water to the target volume, the suspension must pass a wetting test with sedimentation volume above 0.90 after 24 h and redispersibility below 10 manual inversions. Dissolution is determined by USP <711> with paddle speed 50 rpm and medium volume 500 mL. Release testing includes USP <905> uniformity of dosage units, USP <698> deliverable volume after reconstitution, and USP <51> preservative effectiveness where applicable. The terminal product is a single-dose or multi-dose sachet containing granules for oral suspension.

Aseptic filling of the injectable API without terminal sterilization

Injectable solution manufacture begins with dissolution of the API in Water for Injection at a concentration of 5.0–50.0 mg/mL. Tonicity is adjusted with sodium chloride or mannitol to 270–328 mOsm/kg as measured by freezing-point depression per USP <785>. A pH between 4.0 and 7.0 is selected based on API solubility and stability. Before sterile filtration, the bulk solution is passed through a 0.45 µm pre-filter and bioburden is assessed as below 10 CFU/100 mL using membrane filtration. The terminal sterilizing-grade filter is a 0.22 µm polyethersulfone or polyvinylidene fluoride membrane, validated per 21 CFR 211.113 and EU GMP Annex 1 with a bacterial challenge retention above 10^7 CFU/cm² of Brevundimonas diminuta.

Filling is performed in an isolator or RABS maintaining ISO 14644-1 Class 5 at 0.45 m/s unidirectional airflow. A rotary piston pump or peristaltic filler delivers the target fill volume with an overage of 0.5–1.0 mL per vial as described in USP <1151>. Elastomeric stoppers are washed and sterilized by autoclave or gamma irradiation; glass vials are depyrogenated in a tunnel at 300°C with no less than 3 log endotoxin reduction. In-process fill-weight checks are performed every 15 min and adjusted if mean fill weight drifts beyond ±2.0%. Filter compatibility for the API at 5.0–50.0 mg/mL is confirmed by pressure decay and product recovery studies; published data for this specific configuration is limited and requires qualification per batch size.

When the API in solution undergoes hydrolytic or oxidative degradation, the product is lyophilized. The frozen solution is loaded on shelves pre-cooled to −40°C. Freezing is held for 2–4 h. Primary drying is conducted at shelf temperature −20°C to −10°C and chamber pressure 80–200 mTorr; product temperature is maintained below the collapse temperature determined by freeze-dry microscopy. Secondary drying is ramped to 30°C for 6–12 h until residual moisture by USP <921> is below 1.0%. Lyophilized cakes containing 4.0–5.0% w/v mannitol or 2.0–5.0% w/v trehalose exhibit intact, uniform structure without meltback.

Release testing for the injectable dosage form includes sterility per USP <71>, bacterial endotoxins per USP <85>, particulate matter per USP <788>, visible particles per USP <790>, and uniformity of dosage units per USP <905>. Stability testing follows ICH Q1A and ICH Q6A. The terminal product is a single-dose injectable solution or a lyophilized powder for injection.