Pharmaceutical-grade pellet and granule intermediates for oral solid dosage forms and injectable product preparation are engineered particulate APIs with controlled particle size distribution, bulk density, residual moisture, and compressibility characteristics. The product line Pellets & Granules Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable is supplied in four model classes: extrusion-spheronized oral pellets with nominal d50 from 500 µm to 1500 µm, high-shear wet-granulated oral granules with d50 from 150 µm to 850 µm, fluid-bed granulated oral granules with d50 from 250 µm to 600 µm, and sterile injectable granulated API with d90 ≤ 100 µm. Release specifications are controlled by pharmacopoeial methods including Ph. Eur. 2.9.37 and USP <786> for sieve analysis or laser diffraction per ISO 13320:2020, USP <616> for bulk and tapped density, USP <731> for loss on drying, USP <905> for content uniformity, and USP <711> for dissolution where a monograph exists. Residual solvents are controlled to ICH Q3C limits using USP <467>; elemental impurities are controlled to ICH Q3D limits using USP <232>/<233>; microbial quality for non-sterile oral grades is monitored by USP <61> and USP <62>. Sterile injectable grades add bacterial endotoxin per USP <85> with acceptance ≤ 0.25 EU/mg, subvisible particulate matter per USP <788>, and container closure integrity per USP <1207>.

What Distinguishes Extrusion-Spheronized Pellets from High-Shear Granules in Compression and Capsule Filling?

Extrusion-spheronized pellets are dense, nearly spherical units produced by wet massing, extrusion through a screen or dome die, spheronization on a rotating friction plate, and fluid-bed drying. Their geometry yields a narrow particle size distribution and a low interparticulate contact area, which typically produces angle of repose values between 25° and 35°, Hausner ratios between 1.10 and 1.18, and bulk densities from 0.65 g/mL to 0.85 g/mL. High-shear wet-granulated granules are irregular, porous agglomerates formed by impeller and chopper action in a high-shear granulator, followed by wet milling and drying; their angle of repose is typically 30° to 40°, Hausner ratio 1.15 to 1.30, and bulk density 0.45 g/mL to 0.65 g/mL. Compared with simple micronized API, these pellets and granules reduce airborne dust, improve flow, lower segregation risk during transfer, and allow functional coating for modified release. The pellets are generally not directly compressible into tablets unless blended with cushioning excipients; the granules compress more readily because binder distribution creates deformable agglomerates.

On production-scale capsule filling machines using tamping pin or dosator principles, pellets with spherical morphology allow higher fill weights at lower compression forces and reduce the risk of powder bridging, whereas irregular granules may require forced feeding but can pack more readily under tamping to form plugs. On rotary tablet presses, high-shear granules with d50 between 150 µm and 500 µm usually compress into tablets with hardness from 80 N to 200 N at compression force 8 kN to 20 kN; extrusion-spheronized pellets are less directly compressible and tend to fracture or deform elastically unless blended with cushioning excipients such as microcrystalline cellulose and crospovidone.

A 30-station rotary tablet press operating at 45,000 tablets/h with high-shear granules having Hausner ratio above 1.30 can exhibit weight variability exceeding ±5% RSD; addition of 0.25 wt% colloidal silicon dioxide reduces the Hausner ratio and restores die-fill consistency. For capsule filling, extrusion-spheronized pellets with d50 above 1000 µm may require larger capsule body diameters and reduced dosing disc depths to avoid splitting or jamming.

On a production-scale extrusion-spheronization line with a screen aperture of 0.8 mm to 1.2 mm, spheronization plate speed is set between 300 rpm and 800 rpm; plate residence time below 2 min yields elongated or dumbbell-shaped particles, while residence time above 8 min may compact the pellets too densely and reduce dissolution surface area. In high-shear granulation, impeller tip speed is maintained between 5 m/s and 10 m/s; chopper speed is set at 1500 rpm to 3000 rpm for 30 s to 120 s after binder addition. Over-granulation leads to dense agglomerates with narrow pores and low compressibility, requiring re-milling. In fluid-bed granulation, spray rate is adjusted to maintain product temperature above the dew point but below 40°C; inlet airflow is set to achieve a fluidization velocity of 1.5 m/s to 2.5 m/s through the product bowl. Batch-to-batch variance in moisture content of ±0.5% can shift tablet hardness by 15 N to 25 N at a fixed compression force, therefore the IPC at tablet press includes periodic hardness and weight checks every 15 min.

Injectable-grade granulated APIs are manufactured under aseptic conditions with final processing in a Grade A environment according to ISO 14644-1:2015 Class 5. Sterile filtration of a solution prepared from the granulated API is not a substitute for a validated sterilization step if the API itself is non-sterile; therefore, terminal sterilization or aseptic processing must be selected based on heat lability and moisture sensitivity. The sterile injectable model is typically d90 ≤ 100 µm and is filled into depyrogenated glass vials under laminar airflow. Subvisible particle counts are measured by light obscuration using USP <788> Method 1; acceptance requires ≤ 6000 particles per container ≥ 10 µm and ≤ 600 particles per container ≥ 25 µm for small-volume parenterals. Because granulated injectable APIs may be brittle, particle attrition during sieve transfer or vial filling must be controlled; particle size distribution after reconstitution is verified by laser diffraction and should maintain d90 ≤ 100 µm after 30 s of manual swirling.

When Sterile Injectable Granulated APIs Require Endotoxin and Particulate Matter Verification

Bacterial endotoxin verification is mandatory for any injectable-grade pellet or granule because endotoxin removal is not reliably achieved by dry heat alone unless the process is validated to 250°C for 30 min under USP <1228.1> depyrogenation conditions. Batch release testing applies USP <85> with a limit typically ≤ 0.25 EU/mg for parenteral APIs. The risk of endotoxin contamination increases when processing includes aqueous granulation, because Gram-negative bacteria may proliferate in stagnant solutions; therefore, water used in granulation for injectable grades is WFI per USP <1231> and is monitored for conductivity, total organic carbon, and microbial load. Steam sterilization of sealed vials containing granulated API is validated by biological indicator using Geobacillus stearothermophilus spores with a population of 10⁶ per unit and an F0 ≥ 12 min at 121°C when the API is thermostable. For heat-labile injectable APIs, aseptic processing with filtration of the reconstituted solution and lyophilization is used; media fill performance must achieve 0 contaminated units in 5000 filled units per 21 CFR 211.113 and EU GMP Annex 1.

In production-scale lyophilization of injectable granulated APIs, chamber shelf temperature and vacuum are controlled to maintain residual moisture ≤ 1.0%; interruption of the lyophilization cycle above 0°C may collapse the cake and increase reconstitution time. Particulate matter testing on finished containers uses the light obscuration method; Method 2 microscopic particle count is used when the product is a suspension or has high turbidity. For powders intended for reconstitution, USP <788> is applied after reconstitution with the designated diluent, and the diluent is filtered through a 0.22 µm membrane before testing to exclude external contamination.

Drying endpoint control for oral granules is typically set at loss on drying ≤ 2.0% for moisture-sensitive APIs and ≤ 2.5% for direct-compression grades. In fluid-bed drying, inlet air temperature is maintained between 50°C and 70°C, and exhaust temperature is monitored to avoid exceeding 45°C for thermolabile APIs. For hygroscopic APIs, storage below 25°C and ≤ 40% RH is required; if packaging is opened above 60% RH for more than 24 h, re-drying and re-testing of loss on drying and content uniformity are performed before release. Published data for specific equilibrium moisture sorption isotherms of this exact product class is limited; therefore, the above RH threshold is derived from manufacturer technical bulletins for hygroscopic pharmaceutical granulates. The granules should not be blended with acidic buffer species or reactive superdisintegrants such as sodium starch glycolate at high moisture because premature swelling and hydrolytic degradation of acid-labile APIs may occur. For extrusion-spheronized pellets intended for modified-release coating, the pellet surface must remain free of fines below 125 µm; fines are removed by air classification because they cause uneven film thickness and irregular dissolution profiles.

Batch Release Specifications and Pharmacopoeial Test Alignment

Release testing for the oral pellet and granule models includes appearance, identification by FTIR or HPLC, assay by a validated HPLC method, related substances, water content, residual solvents, elemental impurities, microbial limits, and dissolution or disintegration where specified. Content uniformity testing follows USP <905> using 10 units for dosage forms, but for API granules as an intermediate, uniformity of dosage units may be assessed by stratified sampling across 10 locations in the bulk container. Disintegration testing follows USP <701> where the claim is immediate-release; dissolution testing follows USP <711> with apparatus 2 or 1 depending on the dosage form. The acceptable dissolution range is based on the monograph; for extended-release coated pellets, dissolution is performed at multiple time points and pH conditions. For injectable grades, sterility testing according to USP <71> and bacterial endotoxin per USP <85> replace microbial limits.

Cleaning validation for multi-product API pellet and granule facilities is based on maximum allowable carryover calculated from the most potent API and the smallest subsequent batch size. Swab and rinse samples are collected after batch changeover and analyzed by a validated HPLC method with limit of quantitation ≤ 10 ppm of the preceding API. Dedicated equipment is required for penicillin, cephalosporin, and cytotoxic APIs per 21 CFR 211.176 and ICH Q7 Section 5.2, whereas non-dedicated equipment requires three consecutive successful cleaning validation runs. Incompatibilities include contact with strong oxidizing agents during drying at elevated temperature and contact with amine-functionalized excipients for APIs containing ester or lactam moieties, which may initiate degradation to low-molecular-weight impurities. For injectable-grade granules, all product contact surfaces are stainless steel 316L with electropolished finish and are sterilized or depyrogenated before use.