Diosmin EP grade intended for a 450 mg unit dose presents a compaction challenge when processed by direct compression because the micronised flavonoid fraction typically exhibits a bulk density below 0.45 g/cm³, a tapped density below 0.65 g/cm³, and poor mass-flow characteristics. The material is not free-flowing under gravity from an unadapted hopper. The micronised active also shows brittle-fracture behaviour under applied compaction force, and the resulting compact is prone to lamination at high turret speeds. Direct compression is therefore a practical route only when the active is pre-blended with a high-density co-processed excipient matrix and when the press is configured to manage die fill variability. The particle size of the active is controlled by laser diffraction according to ISO 13320:2009; a micronised grade with a D90 below 15 µm is used. A screening core composition contains 450 mg diosmin EP, 80 mg microcrystalline cellulose PH102, 45 mg crospovidone type A, 6 mg colloidal anhydrous silica, 4 mg sodium stearyl fumarate, and 15 mg pregelatinised starch. The concentration of diosmin in this design is 75% w/w, which is at the upper boundary for direct compression; above this level the tensile strength of the compact falls below an acceptable limit. The active is first blended in a bin blender at 10 rpm for 20 min, passed through a 0.8 mm sieve, and then lubricated at 10 rpm for 5 min. Over-mixing at this stage causes the lubricant to line the void spaces and can depress crushing strength. Compression is carried out on a rotary tablet press fitted with 9 mm round concave tooling. Target core weight is 600 mg. The press is set with a pre-compression force of 4 kN and a main compression force of 18–25 kN. Turret speed is held between 20 and 40 rpm because higher speeds increase air entrapment and capping frequency. Ejection force is monitored and should remain below 800 N; a rising ejection force signals insufficient lubrication or tooling wear. The finished cores are tested for crushing strength according to Ph. Eur. 2.9.8. The accepted range is 80–120 N. Friability is evaluated by Ph. Eur. 2.9.7 with a limit of 0.8% weight loss. Disintegration is tested according to Ph. Eur. 2.9.1 in purified water at 37 °C; the core must disintegrate within 15 min. Uniformity of dosage units is verified according to Ph. Eur. 2.9.40 with an acceptance value not greater than 15. Dissolution is performed by USP <711> with 900 mL of 0.5% sodium lauryl sulfate in water at 50 rpm and a time point of 45 min. The direct compression core is subsequently film-coated with an aqueous HPMC-based system to a weight gain of 3% w/w. The terminal product is packaged in PVC/PVDC/aluminium blisters. This direct compression route is not suitable for all production sites because it requires a feed frame paddle speed below 30 rpm to limit particle attrition; published data for this specific configuration is limited, and the process must be confirmed by full-scale press trials.

How Does Micronized Diosmin Alter High-Shear Wet Granulation Endpoint and Drying Behaviour?

High-shear wet granulation is normally preferred over direct compression for high-dose diosmin tablets because the granulated intermediate reduces segregation and improves compaction at lower compression force. The hydrophobic surface of diosmin retards water uptake, so the granulation endpoint is not reached simply by adding a fixed amount of water. The granular mass may appear overwetted at the surface while the core remains dry, and this can lead to non-uniform binder distribution. A representative formulation contains 450 mg diosmin EP, 60 mg lactose monohydrate, 25 mg maize starch, 12 mg povidone K30, 30 mg crospovidone, and 5 mg sodium lauryl sulfate. The sodium lauryl sulfate functions as a wetting agent and is dissolved in the granulating liquid prior to spraying. Granulation is carried out in a top-drive high-shear mixer with an impeller speed of 300 rpm and a chopper speed of 1500 rpm. The granulating liquid is a mixture of purified water and ethanol in a 70:30 ratio; the alcohol improves wetting of the hydrophobic active and shortens the drying phase. The liquid addition rate is controlled at 40–60 g/min/kg. The endpoint is detected by a torque rise of 15–20% above the dry-mix baseline, accompanied by visual conversion of the powder to coarse granules with a mean size of 2–4 mm. A total liquid quantity of 15–22% w/w is typical, but the endpoint must be confirmed for each batch because diosmin particle size and surface area vary. Over-granulation produces dense balls that dry slowly and yield hard granules with reduced dissolution; under-granulation leaves excessive fines that segregate during transfer. The wet mass is discharged through a 2.5 mm screen and dried in a fluid-bed dryer with an inlet air temperature of 50 °C and an exhaust air temperature not exceeding 35 °C. The product temperature is monitored continuously. Drying continues until the loss on drying, determined by Ph. Eur. 2.2.32, is between 2.0 and 3.5%. Over-drying below 1.5% produces brittle granules with increased capping and friability; under-drying above 4.0% causes sticking on the tablet press and microbial growth risk. Dried granules are milled through a 1.0 mm screen and blended with crospovidone before lubrication with 2.0% w/w sodium stearyl fumarate. Compression is performed with 10 mm round concave tooling at a target hardness of 100–140 N. The granulated core may contain residual crospovidone and sodium lauryl sulfate; this formulation is evaluated by Ph. Eur. 2.9.7 for friability, Ph. Eur. 2.9.1 for disintegration, and USP <711> for dissolution. The terminal product is a film-coated tablet with a 3% w/w coating. The granulated route is more robust than direct compression for diosmin loadings above 75% w/w because the wet granulation step creates a more deformable granule shell. However, the ethanol content requires explosion-proof equipment and solvent recovery or a validated drying step to keep residual solvent below the limit specified in Ph. Eur. 2.4.24. Published data for this specific diosmin formulation is limited, so pilot-scale trials are required to establish the torque endpoint threshold for each mixer geometry.

Hard capsule filling with diosmin is carried out with a granulated intermediate because direct powder filling produces unacceptable weight variation on tamping pin and dosator machines. The active has low bulk density and a cohesive character, so it forms voids and clumps inside the dosing chamber, leading to fill weight fluctuations that routinely exceed 5%. A roller-compacted granulate provides a denser and more flowable material for two-piece capsule filling. A working formulation contains 450 mg diosmin EP, 80 mg lactose monohydrate, 60 mg microcrystalline cellulose, 20 mg croscarmellose sodium, 4 mg magnesium stearate, and 3 mg colloidal anhydrous silica. The active and the intragranular excipients are blended in a bin blender and passed through a 0.8 mm sieve. The mixture is compacted on a roller compactor with a roll force of 30 kN/cm and a roll gap of 1.5 mm. The ribbon is milled through a 0.8 mm screen to form granules. The granules are lubricated with magnesium stearate for 5 min and filled into size 00 hard gelatin or HPMC capsules. The target fill weight is 617 mg, and the target lock length is 23.4–23.8 mm. On a dosator capsule machine, the dosing disc thickness is set at 2.4 mm and the compression pin is set to –0.5 mm relative to the dosing chamber to produce a firm plug. On a tamping pin machine, a 3-pin station is used with a pre-compression pressure of 0.5 bar and a final compression pressure of 1.2 bar. The filled capsules are polished and fitted for a security band or seal. Content uniformity is verified by Ph. Eur. 2.9.40. Mass uniformity is checked by Ph. Eur. 2.9.5. Disintegration is tested in purified water at 37 °C with a limit of 15 min according to Ph. Eur. 2.9.1. Dissolution is tested by USP <711> in 900 mL of 0.1% sodium lauryl sulfate in 0.05 M phosphate buffer at 50 rpm and is reported at 45 min. The capsule shell type must be specified because HPMC shells can delay disintegration relative to gelatin at low gastric pH; if HPMC is used, the dissolution test should include a low-pH stage or the product should be stored with desiccant to prevent crosslinking. The terminal product is packaged in PVC/PVDC/aluminium blisters. Capsule filling of diosmin without a granulation step is not recommended on high-speed capsule machines because die fill variability and plug ejection force are unstable. Published data for this exact roller-compaction configuration is limited, and the roll force must be adjusted to ribbon density and mill screen wear.

Injectable Diosmin: Solubilisation Pathways, Filtration Limits, and Precipitation Risks on Dilution

Diosmin as a single-agent injectable is not a standardised compendial dosage form in the European Pharmacopoeia, and no harmonised monograph for diosmin injection exists. Published data for this specific configuration is limited. The principal constraint is the aqueous solubility of diosmin, which is below 10 mg/L in purified water at 25 °C. An injectable solution therefore requires a co-solvent system, a surfactant, a complexing agent, or a combination of these. Weakly acidic phenolic hydroxyl groups permit ionisation at high pH, but exposure to pH values above 9.5 accelerates oxidative degradation and should not be used as the only solubilisation strategy. One development vehicle evaluated for injectable use contains 10 mg/mL diosmin in 30% v/v polyethylene glycol 400, 20% v/v ethanol, 10% v/v propylene glycol, and water for injection. The solution is adjusted to pH 8.0 with trometamol. This vehicle is not an approved formulation and is used only to illustrate the solubilisation challenge. The co-solvent mixture is prepared under nitrogen to limit oxygen exposure. Diosmin is added slowly with high-shear mixing at 500–1000 rpm until dissolved, and the bulk solution is held at 20–25 °C for not more than 8 h before filtration. Sterile filtration is performed through a hydrophobic or low-protein-binding 0.22 µm polyvinylidene fluoride membrane. Polyethersulfone membranes can adsorb flavonoids and cause active loss; if PES is used, membrane binding must be quantified. The filtration train is pre-conditioned with the vehicle without the active to saturate adsorption sites. Filtration pressure is kept below 1.0 bar to prevent precipitation from pressure-induced phase separation. The filtered solution is filled into amber Type I glass vials under a nitrogen headspace and sealed with bromobutyl rubber stoppers. Terminal sterilisation by autoclaving at 121 °C should not be selected without forced degradation data showing no increase in specified impurities; aseptic filtration is the more conservative route. The final product is tested for sub-visible particles according to Ph. Eur. 2.9.19 and visible particles according to Ph. Eur. 2.9.20. The sub-visible particle count per container must not exceed 6000 particles at 10 µm and 600 particles at 25 µm per 100 mL. Bacterial endotoxins are tested by Ph. Eur. 2.6.14. The endotoxin limit is derived from the maximum bolus dose and is typically not more than 0.5 EU/mg of diosmin if the dose is 10 mg/kg. Osmolality is adjusted to 280–320 mOsm/kg by addition of glycerol or glycerol plus sodium chloride; sodium chloride alone may reduce co-solvent capacity and induce precipitation. In-use dilution with 0.9% sodium chloride or 5% glucose must be validated, because co-solvent concentrations below 20% v/v can produce visible precipitation. The dilution study should include dynamic light scattering and visual inspection at 5 °C, 25 °C, and 40 °C for at least 24 h. A final formulation for injectable diosmin would also require photostability testing according to ICH Q1B because flavonoid aglycones are sensitive to light. The terminal product is stored at 2–8 °C in amber glass; room-temperature storage is not recommended without proof of chemical stability. Injectable diosmin is therefore technically feasible but operationally demanding; the process boundary is defined by filtration membrane compatibility, pH, oxygen control, and dilution media.

Oral granules in sachets are used when a single-dose diosmin preparation is intended to be dispersed in water or sprinkled onto soft food. The active is manufactured as a dry granulate with a bulk density above 0.60 g/cm³ to ensure accurate filling on sachet machines. A typical formulation contains 450 mg diosmin EP, 4500 mg sorbitol, 500 mg xylitol, 100 mg xanthan gum, 20 mg colloidal anhydrous silica, and 30 mg lemon flavour. The granulating liquid is a hydroalcoholic solution of povidone K30 at 5% w/w. Diosmin is pre-blended with one third of the sorbitol in a high-shear mixer to break down agglomerates. Xanthan gum is dry-blended with the remaining sorbitol to prevent lump formation when the granulate is later dispersed. The hydroalcoholic binder is sprayed onto the fluidised powder bed in a fluid-bed granulator with an inlet air temperature of 55 °C, a spray rate of 12 g/min/kg, and an atomising air pressure of 2.0 bar. The granulation endpoint is determined by a product temperature of 38–40 °C and visual grain formation; the loss on drying is controlled between 1.0 and 2.0% by Ph. Eur. 2.2.32. The dried granules are sieved through a 1.4 mm screen to remove oversized material. The granules are then filled into aluminium foil/polyethylene laminate sachets at 5.0 g per unit. The packaging line is maintained at relative humidity below 25% because sorbitol-based granules absorb moisture and become sticky. Each sachet is sealed with a minimum seal width of 2.0 mm and a heat seal strength above 5 N/15 mm. The finished sachet is tested for content uniformity by dispersing the entire contents and analysing an aliquot according to Ph. Eur. 2.9.40. Disintegration is not applicable to this dosage form; dispersibility is assessed by adding one sachet to 100 mL of water at 20 °C and stirring gently for 2 min. The resulting dispersion should pass through a 0.71 mm sieve. Sedimentation volume is recorded after 30 min and should remain above 0.9 due to the xanthan gum. pH is controlled between 5.5 and 7.5. Dissolution is tested according to USP <711> using 900 mL of 0.5% sodium lauryl sulfate at 50 rpm and is reported at 45 min. The terminal product is for oral dispersion and should not be packaged in clear sachets if the active is exposed to light during storage; amber sachet laminate or a secondary carton is required. The main processing failure mode is caking of the dry granulate in the sachet filler hopper due to static charge and moisture ingress. This is controlled by humidification below 25% RH and by adding colloidal anhydrous silica at 0.4% w/w. Batch-to-batch variance in diosmin particle size alters dispersion colour and sedimentation; therefore the active is sieved before use and the drying endpoint is fixed by water content rather than by time.

When a Diosmin/Hesperidin Fixed-Dose Combination Is Film-Coated Without a Subcoat

Fixed-dose combination tablets containing 450 mg diosmin and 50 mg hesperidin are produced for venous insufficiency therapy. Aqueous film-coating of this core is more demanding than coating conventional soluble actives because the flavonoid core is hydrophobic and brittle. If the coating pan is operated without a subcoat, the first aqueous spray introduces water at the core surface and can soften the outer granule layer, producing edge chipping and logo bridging. The core also has low thermal conductivity, so evaporative cooling from the spray creates a wet surface that persists longer than expected. A subcoat is applied first using low-viscosity HPMC E3 at 1.0% w/w solids in purified water. The subcoat is sprayed in a perforated pan at a pan speed of 8–10 rpm, an inlet air temperature of 60 °C, an exhaust air temperature of 42–45 °C, an atomising air pressure of 0.2 bar, and a spray rate of 2.0–3.0 g/min/kg. This subcoat seals the core before the colour coat is applied. The colour coat is an aqueous HPMC-based dispersion containing titanium dioxide and iron oxide at a total solids concentration of 12% w/w. The colour coat is applied to a target weight gain of 3% w/w. The same pan is used, but the spray rate is increased to 4.0–5.0 g/min/kg and the inlet air temperature is reduced to 55 °C to avoid surface drying of the coat. The coating process is interrupted if the exhaust relative humidity exceeds 60%, because excessive moisture uptake can delay disintegration below 15 min and promote adhesion of the film to the pan walls. The coated tablets are tested for disintegration by Ph. Eur. 2.9.1 in purified water at 37 °C. The core must disintegrate within 15 min; the subcoat must not extend disintegration beyond this limit. Friability is tested on uncoated cores only by Ph. Eur. 2.9.7 with a limit of 0.8%. Dissolution is performed by USP <711> using 900 mL of 0.5% sodium lauryl sulfate at 50 rpm with a time point of 45 min. The film coat is not a rate-controlling membrane; it is applied for appearance, light protection, and ease of swallowing. The final product is packaged in PVC/PVDC/aluminium blisters. A moisture vapour transmission rate below 0.35 g/m²/day at 38 °C/90% RH is preferred because the micronised active may agglomerate under humid conditions and reduce dissolution. Batch experience shows that the main failure mode in scale-up is overwetting during the first 10 min of the subcoat phase; operating below the dew point of the incoming air eliminates this failure. If a subcoat is omitted, the initial colour coat spray must be reduced to 1.5 g/min/kg and the pan speed reduced to 6 rpm, but the risk of logo bridging remains high. Published data for this specific fixed-dose combination is limited, and the coating parameters must be verified in the selected pan geometry because the film thickness distribution is scale-dependent.