Ciclosporin Capsule Fill and Shell Compatibility

Soft gelatin capsule processing with Ciclosporin Pharma Grade API does not proceed by dry-powder filling. The API is a cyclic undecapeptide of molecular mass 1202.61 g/mol, practically insoluble in water with an aqueous solubility near 0.04 mg/mL at 25 °C, and it requires a lipid-based preconcentrate to generate a kinetically stable microemulsion upon contact with gastrointestinal fluid. The fill vehicle is formulated in the working range of 10-30% w/w medium-chain triglyceride or caprylic/capric triglyceride as the lipophilic phase, 20-50% w/w macrogol glycerol hydroxystearate or polyoxyethylated castor oil as the hydrophilic surfactant, and 10-30% w/w absolute ethanol/propylene glycol as the co-solvent; the API loading in the fill mass is typically 10-20% w/w. Phase behavior is assessed by dispersing the preconcentrate into simulated gastric fluid pH 1.2 without enzyme and simulated intestinal fluid pH 6.8, then measuring droplet size by dynamic light scattering according to ISO 22412:2017. A microemulsion is considered acceptable only if the z-average droplet diameter remains below 50 nm after 1:50 aqueous dilution; larger droplet populations indicate a coarse emulsion that may reduce the absorption rate. The gelatin shell is a structural weak point because ethanol and propylene glycol migrate from the fill into the gelatin matrix, plasticizing the shell and increasing the risk of seal failure, leakage, and capsule-to-capsule mass variation. The fill is deaerated under vacuum before encapsulation, and nitrogen blanketing is applied throughout mixing and storage to limit peroxide formation from the triglyceride phase. The shell is cast with a gel strength suitable for plasticizer migration, and filled capsules are dried at 20-25 °C and 30-40% RH until the shell moisture content determined by USP <921> Method Ia falls within the product-specific acceptance window. Packaging in cold-form aluminum-aluminum blisters with a desiccant sachet is used because PVC/PVDC blisters do not provide an adequate barrier against ethanol loss and moisture ingress. In-process controls include fill-mass uniformity, shell thickness, seal strength, and residual oxygen in the headspace. Release testing includes assay by USP <621>, dissolution by USP <711> Apparatus II, and water content by USP <921>. The dissolution medium for Ciclosporin capsules is typically an acidic medium with surfactant; the exact medium composition and paddle speed must be justified during method development because the microemulsion preconcentrate can release the drug so rapidly that a method without surfactant may fail to discriminate between acceptable and unacceptable batches.

Can Direct Compression Deliver a Bioequivalent Ciclosporin Tablet?

Direct compression of crystalline Ciclosporin API is not feasible at production scale because the API has poor aqueous solubility, high lipophilicity, and poor flow from a hopper; the resultant tablets would show incomplete dissolution and high inter-tablet variability. A formulation route based on amorphous solid dispersion is required. Hot-melt extrusion on a co-rotating twin-screw extruder with an L/D 40:1 barrel and gravimetric feeding is one route; the API is blended with a polymer such as hypromellose acetate succinate or polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer in a drug-to-polymer ratio of 1:1 to 1:5 w/w. The barrel temperature must remain above the glass transition temperature of the polymer to obtain a homogeneous melt, but below the degradation threshold of Ciclosporin; thermal excursions above 170 °C are avoided because degradation products of the cyclic peptide can appear under prolonged residence time. The melt is extruded through a die plate, cooled on a stainless-steel conveyor, milled, and then blended with microcrystalline cellulose, crospovidone, and sodium stearyl fumarate before compression on a rotary tablet press with precompression. Published data for specific Ciclosporin hot-melt extrusion formulations are limited; therefore the thermal behavior of the API-polymer dispersion should be verified by differential scanning calorimetry according to ASTM E1356 and thermogravimetric analysis according to ASTM E2550 during preformulation. The absence of a recrystallization exotherm in the milled extrudate after storage at 40 °C/75% RH for 1 month is a minimal stability indicator, while dissolution is tested using USP <711> Apparatus II with a surfactant-containing medium. Tablet hardness is controlled by USP <1217>, friability by USP <1216>, and uniformity of dosage units by USP <905>. Because the amorphous form is thermodynamically metastable, the operational boundary is narrow: excess moisture during compression can cause agglomeration; insufficient moisture can reduce tablet hardness due to poor bonding of milled dispersion particles. The compression environment is therefore maintained at 20-25 °C and 35-45% RH.

For single-dose sachets and granules that can be sprinkled onto soft food, fluid-bed granulation is selected when swallowing a capsule is not acceptable and dose fractionation at the bedside is required. The Ciclosporin API is first micronized or co-milled with a hydrophilic carrier to improve surface wetting, then dispersed in a binder solution, usually hypromellose E5 in purified water, and sprayed onto a fluidized bed of lactose monohydrate and pregelatinized starch in a top-spray fluid-bed processor. The granulation process window is narrow because the cyclic peptide is sensitive to hydrolytic degradation in the presence of free water at elevated temperature; therefore the inlet air temperature is maintained below 70 °C, the product temperature below 40 °C, and the final granule moisture content by USP <921> below 3.0% w/w. Binder concentration is held at 2-5% w/w of dry granulate, and the API content per sachet is adjusted by geometric dilution from 15 mg to 100 mg per dose. The dried granules are screened through a 1.0 mm sieve and filled into triple-layer aluminum sachets under low humidity. The terminal granule product must pass dissolution testing by USP <711> Apparatus III or Apparatus II, content uniformity by USP <905>, and loss on drying by USP <731>. Because granules are not a monolithic dosage form, the dissolution procedure must be adapted to account for the absence of compression; the use of a surfactant-containing medium is usually required to maintain sink conditions, and the method must be validated according to ICH Q2(R1) for linearity, accuracy, and precision. These granules are not interchangeable with reconstituted suspensions at the point of administration unless a documented equivalence study has been performed.

Injectable Concentrate Dilution, Polyoxyethylated Castor Oil, and DEHP Leaching

The injectable concentrate pathway centers on dissolution of Ciclosporin in a vehicle of polyoxyethylated castor oil and absolute ethanol under nitrogen, yielding a sterile concentrate at 50 mg/mL API. This vehicle is selected because Ciclosporin has negligible solubility in purely aqueous media; however, the surfactant fraction introduces a clinical risk of anaphylactoid reactions when the undiluted concentrate is administered rapidly. The concentrate must therefore be diluted with 0.9% sodium chloride injection or 5% dextrose injection to a final concentration of 0.5-2.5 mg/mL before intravenous infusion. Glass or polyolefin containers are specified for the admixture; PVC containers are not used because polyoxyethylated castor oil can extract di(2-ethylhexyl) phthalate from PVC tubing and bags, creating a leachable risk that is evaluated by USP <661.1> and ICH Q3C residual-solvent guidance. Filtration uses a sterilizing-grade 0.22 µm polyvinylidene fluoride membrane, and the fill-finish operation is performed by aseptic processing rather than terminal moist-heat sterilization because the cyclic peptide degrades at high temperature; sterility is confirmed by USP <71>, bacterial endotoxins by USP <85>, and particulate matter by USP <788>. An injectable-grade Ciclosporin API lot must meet a tighter bacterial endotoxin specification than oral-grade material; the exact limit is derived from the maximum dose and route of administration under USP <85> and is reported on the Certificate of Analysis. The dilution line is an additional processing step where pH shifts or insufficient mixing can cause precipitation of the peptide; the diluted admixture should be inspected visually for turbidity or particulate formation and should not be combined with other drugs in the same infusion container without documented compatibility. Published data for specific admixture stability are limited and should be generated on-site using HPLC assay by USP <621>; the stability window is not assigned as a universal value because it depends on container material, storage temperature, and admixture concentration.

When a ready-to-dispense oral liquid is required, the API is not simply suspended in water because of its low aqueous solubility and bitter taste; instead, a microemulsion preconcentrate is supplied as an oral solution to be diluted in milk, chocolate milk, or orange juice immediately before intake. The concentrate contains Ciclosporin at 100 mg/mL, corresponding to approximately 10% w/v API, in a vehicle of ethanol, medium-chain triglycerides, and a hydrophilic surfactant. The co-solvent fraction is sufficient to fully dissolve the API and prevent precipitation upon aqueous dilution; if ethanol content is too low, precipitation occurs in the dilution beverage; if too high, palatability and container compatibility issues increase. The concentrate is filled into amber glass bottles with a calibrated oral syringe to achieve dose accuracy; glass is used because ethanol permeability through plastic can reduce co-solvent content and shift phase behavior. The patient-specific dose is mixed with the beverage, and the microemulsion is stable enough for prompt administration, but the mixture should not be stored for extended periods because beverage components can alter droplet size and release kinetics. Quality tests include deliverable volume by USP <698>, assay by USP <621>, alcohol content by USP <611>, and microbial examination of nonsterile products by USP <61> and USP <62>. In-use stability after first opening must be justified, and the multidose container is assigned an in-use period based on microbial challenge data.