On direct compression lines handling bendazol API at a target content of 20 mg per unit, the critical input variable is not chemical purity alone but the particle-size distribution after delumping and the residual moisture in the drug substance. Material with D90 above 250 µm from primary crystallisation segregates in low-dose blends and triggers content uniformity failures under Ph.Eur. 2.9.40 when the total core mass is below 100 mg. A pre-milled fraction with D90 between 75 µm and 150 µm and D10 between 5 µm and 20 µm is therefore maintained before dry blending with microcrystalline cellulose, pregelatinised starch, and crospovidone. The finished blend is sampled at 10 locations during tumble mixing at 25 rpm for 20 min; acceptance criteria are 95.0–105.0% label claim and RSD not more than 5.0% according to USP <905>.

The direct compression route is limited by bendazol blend flow and segregation behaviour. If the API particle size D90 exceeds 200 µm and microcrystalline cellulose content is below 60% w/w, the blend tends to segregate in the press hopper after 30 min of operation. Compression is performed on a rotary tablet press with 6 mm round tooling, precompression force 2–4 kN, main compression force 8–15 kN, and turret speed 30–60 rpm. Ejection force is monitored continuously; values above 500 N indicate insufficient lubrication or excessive moisture. Finished cores are tested for hardness, friability, and disintegration according to Ph.Eur. 2.9.8, 2.9.7, and 2.9.1 / USP <1217>, <1216>, <701>; typical release limits are hardness 40–80 N, friability not more than 1.0%, and disintegration not more than 15 min in 900 mL water at 37 ± 2 °C. Content uniformity testing follows Ph.Eur. 2.9.40 / USP <905>, with an acceptance value ≤15 for 10 units. Dissolution testing under USP <711> apparatus II at 50 rpm in 900 mL of 0.1 M hydrochloric acid is used as a batch-release control; a Q value of not less than 80% at 30 min is applied. The terminal product is a round, uncoated or film-coated immediate-release tablet in PVC/aluminium blister. Film coating with hypromellose-based systems adds no more than 2.0 mg per core and requires inlet air temperature 50–60 °C, atomising air pressure 1.0–1.5 bar, and pan speed 8–12 rpm; coating pan humidity is held below 50% RH to avoid reabsorption of surface moisture. Pre-drying of bendazol API at 60 °C for 2 h under vacuum is recommended when loss on drying according to Ph.Eur. 2.2.32 / USP <731> exceeds 1.0% w/w. Direct compression is not recommended when ambient relative humidity exceeds 60% RH because the API-containing blend can absorb surface moisture and increase ejection force.

Why Does Low-Dose Bendazol Capsule Filling Drift After 30-Minute Blending in V-Blenders?

Capsule filling for bendazol at a 20 mg fill weight inside a size 3 hydroxypropyl methylcellulose shell requires a premix step that is shorter and gentler than tablet blending. The active fraction is first geometrically diluted with mannitol or pregelatinised starch in a 1:5 ratio using a low-shear V-blender operated at 15 rpm for 5 min; this premix is then passed through a 500 µm conical mill to break soft agglomerates. The main blend is filled into empty HPMC capsules on a dosator-type capsule machine with pin plate speed calibrated to deliver 250 mg ± 5.0% per shell. Weight variation is checked every 15 min according to Ph.Eur. 2.9.5 / USP <905>; individual capsule weights must be within 90.0–110.0% of the mean and not more than two of 20 units outside the limit. Content uniformity for the 20 mg dose is controlled at the blend stage using Ph.Eur. 2.9.40; the acceptance value is ≤15. Because bendazol is a low-dose active, the capsule powder blend is lubricated with not more than 0.5% w/w magnesium stearate and 0.5% w/w colloidal silicon dioxide to avoid excessive hydrophobicity of the plug. Dissolution testing on filled capsules follows USP <711> apparatus II in 900 mL 0.1 M hydrochloric acid at 50 rpm; the Q value at 30 min is not less than 80%. The terminal product is a size 3 HPMC capsule, unprinted, packaged in aluminium/aluminium cold-form blister to limit moisture ingress below 0.5 mg/day per blister.

The drift in capsule fill weight after 30 min of V-blending is most often caused by electrostatic charge accumulation on bendazol fines and mannitol particles. The charge build-up raises the angle of repose and reduces bulk density of the pre-blend, which changes the dosator piston compression ratio. Storage of the bendazol premix at 25 °C and 35% RH for 12 h before filling and the addition of 0.1% w/w sodium stearyl fumarate as a charge-control agent are process adjustments used to stabilise dosator weight. If fill weight RSD exceeds 3.0%, the filling line should be stopped and the powder bed remilled through a 800 µm screen. Capsule-specific incompatibility is limited; however, gelatin shells are not selected for bendazol when the fill powder moisture by Karl Fischer according to USP <921> method Ia exceeds 4.0%, because soft gelatin can cross-link and delay dissolution. Published data for bendazol capsule formulations under ICH Q1A stability testing are limited; therefore, confirmatory photostability and open-dish studies are required before launch.

Wet Granulation Route for Bendazol Tablet Cores Requires Binder Solution Viscosity Below a Critical Threshold

When a bendazol tablet core is manufactured by high-shear wet granulation, the granulating liquid is an aqueous povidone K30 solution with a viscosity controlled between 5 mPa·s and 25 mPa·s at 25 °C. The dry powder mixture consists of bendazol 20 mg, lactose monohydrate 45 mg, microcrystalline cellulose 25 mg, croscarmellose sodium 5 mg, and colloidal silicon dioxide 0.5 mg per unit. The granulator is a top-drive high-shear mixer with impeller speed 200 rpm and chopper speed 1500 rpm; the binder solution is added at 5 g/min per kilogram of dry mix through a nozzle at 1.0 bar atomisation. The wet mass endpoint is reached when the power consumption of the impeller rises 30% over the dry blend baseline, or when the granulate can be manually compressed without water expression. The wet granules are milled through an 800 µm screen and immediately transferred to a fluid bed dryer with inlet air temperature 60 °C and target product temperature 35 °C. Drying is stopped when loss on drying by Ph.Eur. 2.2.32 / USP <731> is 1.5–2.5% w/w. The dried granulate is calibrated through an 600 µm screen and blended with magnesium stearate 1.0 mg per unit for 3 min in a bin blender at 10 rpm. The lubricated granulate is compressed on a rotary tablet press to a hardness of 60–100 N and a disintegration time of not more than 15 min, as measured by Ph.Eur. 2.9.1 / USP <701>. The terminal product is a film-coated tablet containing 20 mg bendazol, with the coating weight being 3.0% w/w of the core. The granulation route is selected when direct compression fails due to poor flow or when the bendazol input lot has a D90 below 50 µm and a bulk density below 0.40 g/mL according to Ph.Eur. 2.9.34 / USP <616>. In that case, wet granulation provides a denser granulate with improved flow and reduced segregation. The binder solution viscosity threshold is critical because solutions above 30 mPa·s create overwet masses that blind the 800 µm screen and overgranulate the active, resulting in slower dissolution and increased tablet hardness variability. Release criteria for bendazol granules prior to compression are: LOD 1.0–3.0%, bulk density 0.45–0.65 g/mL, tapped density 0.55–0.75 g/mL, and compressibility index 15–25% according to Ph.Eur. 2.9.36 / USP <1174>.

If the product temperature in the fluid bed exceeds 50 °C, the colour of the bendazol wet granulate can shift from off-white to pale yellow, and the dissolution Q value may drop below 80% at 30 min. Therefore, the drying curve is monitored with a probe and the inlet air dew point is kept below 5 °C to avoid surface moisture collapse. The final blend is sampled for content uniformity at 10 locations; acceptance is 95.0–105.0% label claim with RSD not more than 4.0%. Dissolution testing under USP <711> apparatus II at 50 rpm in 0.1 M HCl is carried out on compressed cores before coating, at Q 80% in 30 min. This route is preferred for bendazol tablet lots above 100 kg because wet granulation tolerates lot-to-lot variability in API particle size better than direct compression, provided the binder viscosity threshold is respected.

In parenteral 1% bendazol solution processing, the drug substance is manipulated as a single-phase liquid rather than as a particulate solid. The formulation is prepared in Water for Injection at a concentration of 10 mg/mL, with sodium chloride added at 9 mg/mL as an isotonicity agent and the pH adjusted to 3.0–3.5 with 0.1 M hydrochloric acid to maintain the benzimidazole active in protonated solution. The compounding vessel is a closed stainless steel tank with bottom magnetic stirrer and nitrogen overlay; the solution temperature is maintained at 20–25 °C during pH adjustment. After complete dissolution, the solution is prefiltered through a 0.45 µm polyethersulfone filter and then sterile-filtered through a 0.22 µm polyvinylidene fluoride membrane under a differential pressure of not more than 1.0 bar. The sterile filtrate is filled into 1 mL low-density polyethylene ampoules under Grade A aseptic conditions; fill volume is 1.05 mL ± 0.10 mL to compensate for holdup. The sealed ampoules are tested for leakage using high-frequency vacuum dye bath at not less than 0.6 bar. Terminal product is an injectable 1% bendazol solution, 1 mL per ampoule, packaged in PVC trays. Release testing includes bacterial endotoxin according to Ph.Eur. 2.6.14 / USP <85> with a limit of not more than 0.25 EU/mg of bendazol, sterility according to Ph.Eur. 2.6.1 / USP <71>, particulate matter according to Ph.Eur. 2.9.19 / USP <788>, pH according to Ph.Eur. 2.2.3 / USP <791>, and assay by HPLC at 95.0–105.0% label claim. The following table summarises the parenteral release matrix.

Because bendazol injection is an aqueous solution at acidic pH, the critical process risk is particulate formation from incomplete dissolution or pH drift during storage. Dissolution of the 10 mg/mL API is considered complete only after the solution passes a turbidimeter limit of not more than 1.0 NTU. The solution is not autoclaved if the forced degradation data at 121 °C for 15 min show assay loss above 2.0% or an increase in total related substances greater than 0.5%. In such cases, aseptic filtration is the selected sterilisation method, and the holding time from sterile filtration to filling is capped at 12 h at 15–25 °C to limit bioburden recovery risk. Published data for bendazol parenteral degradation kinetics under ICH Q1A conditions are limited; therefore, the formulation laboratory must generate pH-rate profiles before fixing the sterilisation route. The injectable terminal product should not be stored at pH above 5.0 because the free base can precipitate and produce subvisible particles. Compatibility with rubber stoppers and glass ampoules is confirmed by accelerated stability at 40 ± 2 °C / 75 ± 5% RH for 6 months; a negative control against uncoated glass is included to detect glass surface interaction.

If Terminal Sterilisation at 121 °C Is Applied to Bendazol Ampoules, pH Drift and Subvisible Particle Formation Define the Release Profile

For bendazol injection batches that are terminally sterilised at 121 °C, the release profile is governed by pH drift, assay loss, and subvisible particle formation rather than by simple sterility data alone. The ampoules are processed through a superheated water cascade autoclave at 121 °C for 15 min, with load probes inserted into the coldest ampoule location. The F₀ value is calculated from the probe data and must exceed 8 min for routine release according to Ph.Eur. 5.1.1. The process is valid only if the ampoules are filled under nitrogen and the headspace oxygen concentration is less than 2.0%. Under these conditions, the main degradation pathway is pH-dependent hydrolysis of the benzimidazole ring, which can produce a yellow chromophore. The pH of the formulation is therefore rechecked after terminal sterilisation; a drift of more than 0.3 pH unit is a batch rejection criterion. Assay loss after the autoclave cycle is limited to not more than 2.0% relative to the pre-sterilised solution, and total related substances are limited to not more than 1.0% area by HPLC. Subvisible particle testing after terminal sterilisation is performed by light obscuration according to Ph.Eur. 2.9.19 / USP <788>; the counts must not exceed 6000 particles ≥10 µm and 600 particles ≥25 µm per container. The terminal product is a sterile 1% bendazol injection in 1 mL glass ampoules. If the particle counts exceed these limits, the batch is not reprocessed by filtration because the particles are degradation products, not filterable contamination.

The autoclave route is not selected for bendazol when the product pH is above 4.5, because free base precipitation accelerates during heat-up and cooling. In addition, terminal sterilisation is incompatible with plastic ampoules if the ampoule material has a heat deflection temperature below 121 °C; low-density polyethylene can deform and compromise seal integrity. The thermal sterilisation route is therefore reserved for glass ampoules only. The loading pattern in the autoclave is designed to avoid direct steam impingement on ampoule tips; perforated stainless steel trays with a maximum load of 150 ampoules per tray are specified. The post-sterilisation visual inspection is performed at 10 000 lux against black and white backgrounds to detect cracked ampoules, charred particles, and colour change. The injection terminal product, when terminally sterilised, carries a release tag with the F₀ value, the post-cycle pH, the assay, and the subvisible particle counts. This data set aligns with the batch release expectations of European Pharmacopoeia chapter 5.1.1 and EU GMP Annex 17 for real-time release parameters.

Oral Granule Sachet Filling and Moisture Scavenger Selection for Bendazol 20 mg Unit Doses

Oral granule sachet filling for bendazol 20 mg unit doses is performed by dry granulation because the moisture introduced by wet granulation would require drying above 50 °C. Bendazol oral granules are produced by roller compaction and filled into sachets at a unit dose of 20 mg bendazol per 1.0 g of finished granules. The dry premix consists of bendazol 20 mg, mannitol 500 mg, sucralose 5 mg, and citric acid 20 mg; the mixture is roller compacted on a chilsonator with roll force 25 kN/cm, roll speed 5 rpm, and screen size 800 µm. The resulting granules have a bulk density of 0.50–0.65 g/mL according to Ph.Eur. 2.9.34 / USP <616>. The granules are filled into four-side-seal sachets on a vertical form-fill-seal machine with a fill weight of 1.00 g ± 5.0%. Each sachet is heat-sealed at 140 °C for 0.8 s, and the seal integrity is tested by dye leak test according to ASTM F1929-15; the acceptance criterion is no dye penetration beyond 5% of the seal width. Content uniformity of sachet dose is checked by sampling 10 sachets from beginning, middle, and end of the filling run; acceptance value is ≤15 according to Ph.Eur. 2.9.40. The terminal product is a single-dose granule sachet intended for reconstitution or direct oral administration. Moisture content of the finished sachet is controlled by Karl Fischer according to USP <921> method Ia; the limit is not more than 2.0% w/w. Each sachet contains a silica gel strip if the packed product is intended for climate zone IV distribution; the desiccant weight is 1.0 g per 10 sachets. The moisture scavenger selection must avoid silica gel dust affecting granule flow and must not contain cobalt chloride, which is restricted under Regulation (EC) No 1272/2008, Annex VI.

Stability testing of bendazol oral granules follows ICH Q1A R2 long-term conditions of 25 ± 2 °C / 60 ± 5% RH and intermediate conditions of 30 ± 2 °C / 65 ± 5% RH; accelerated testing is conducted at 40 ± 2 °C / 75 ± 5% RH for 6 months. The granule product specification includes identity, assay 95.0–105.0% of label claim, related substances not more than 1.0%, water content not more than 2.0%, and microbial limits according to Ph.Eur. 5.1.4 / USP <61> and <62>. If citric acid is included as a pH modifier, the tensile strength of the sachet seal after 6 months at 40 °C must remain above 15 N/15 mm to avoid seal rupture. Process validation of the roller compaction step is based on granule size distribution, bulk density, and the absence of compacted flakes exceeding 2.0 mm. Published data for this specific bendazol granule design are limited; the manufacturing acceptance criteria are therefore verified on three consecutive industrial-scale batches before release.