Chorionic gonadotrophin is a heterodimeric glycoprotein with a molecular mass of approximately 37,000 Da and a carbohydrate content that influences both specific activity and solution stability. Oral tablet, capsule, and granule presentations are not mapped in this application section because gastrointestinal proteolysis destroys the intact dimer before systemic absorption; no USP/Ph. Eur. oral solid dosage monograph exists, and published pharmacokinetic data for oral hCG are limited to non-commercial experimental configurations. The downstream segments below are therefore confined to sterile injectable and veterinary/aquaculture uses in which the API is handled as a lyophilised powder or aseptic liquid and potency is expressed in international units per vial, per animal, or per kilogram body weight.

Manufacturing a lyophilised injection for ovulation induction and final oocyte maturation in assisted reproductive technology begins with potency assignment of the API lot against the International Standard for chorionic gonadotrophin, because the glycoprotein is not dosed by mass. A 5,000 IU or 10,000 IU label claim is achieved by calculating the mass from the lot-specific activity in IU/mg; the API is dissolved in Water for Injections with a bulking agent such as mannitol and phosphate buffering salts, filtered through a sterilising-grade 0.22 μm membrane, and filled into depyrogenated Type I borosilicate glass vials under EU GMP Annex 1:2022 Grade A conditions within an ISO 14644-1:2015 Class 5 zone. The filled vials are partially stoppered and lyophilised in a shelf lyophiliser with temperature-mapped shelves; cycle development uses freeze-drying microscopy to establish the collapse temperature, and the cycle must balance primary drying above the collapse region against residual moisture control. Batch-to-batch variance in specific activity, protein aggregation during freezing, and moisture ingress after stoppering are the main processing bottlenecks observed on production-scale lyophilisers; terminal residual moisture is measured by Karl Fischer titrimetry under USP <921>, sterility by USP <71>, and potency by compendial bioassay. Published quantitative lyophilisation cycle parameters for this specific API are limited, so each manufacturer must justify the selected freezing ramp, chamber pressure, and secondary drying temperature through formulation-specific physical characterisation. The terminal product is a sterile lyophilised plug in a single-dose or multi-dose Type I glass vial for reconstitution and intramuscular or subcutaneous injection.

How Does a Multi-Dose Presentation Alter Preservative Selection and In-Use Stability Validation?

Long-term administration in hypogonadotropic hypogonadism places a multi-dose presentation under stricter preservative and in-use stability requirements than a single-use ART trigger. When a 10,000 IU lyophilised powder is reconstituted with 10 mL of diluent, the nominal concentration is 1,000 IU/mL; the diluent may contain an antimicrobial preservative such as benzyl alcohol, and its activity must be confirmed by antimicrobial effectiveness testing under USP <51> or Ph. Eur. 5.1.3. The production process is split into two sterile streams: the API solution is aseptically filtered through a 0.22 μm membrane and lyophilised, while the preservative-containing diluent is either terminally sterilised at 121 °C for 15 minutes when heat-stable or aseptically filtered when heat-labile. Compatibility of the preservative with the glycoprotein after reconstitution is a process constraint; preservative-induced aggregation or subunit dissociation must be excluded by high-performance size-exclusion chromatography and potency assay during in-use stability. After reconstitution, the multi-dose product must have a validated in-use storage period supported by chemical stability, sterility, and preservative efficacy data generated under ICH Q1A(R2); the allowable storage window is product-specific and cannot be extrapolated from one formulation to another. This presentation is not suitable for neonatal or infant use because of preservative-related toxicity, which creates a separate requirement for preservative-free single-dose presentations. Terminal product type: powder and solvent for solution for injection, multi-dose, for intramuscular or subcutaneous administration.

Compounded sterile HCG preparations occupy a separate regulatory pathway from finished pharmaceutical manufacturing and are used by reproductive endocrinology clinics when a licensed presentation is not available or when a patient-specific dose would otherwise require administration from multiple vials. In a USP <797>-governed pharmacy, the compounding sequence is performed inside an ISO 14644-1:2015 Class 5 primary engineering control located within an ISO Class 7 buffer area; the operator transfers a lyophilised 10,000 IU vial to the aseptic workspace, reconstitutes with the manufacturer-approved diluent to a nominal concentration of 1,000 IU/mL, and withdraws the prescribed number of international units into sterile polypropylene syringes. The compounding record calculates each syringe as IU, not as a mass-based percentage, because the API is already present as a lyophilised cake and the only variable is dilution volume. Beyond-use dating is assigned according to the compounding risk category and storage conditions in USP <797>; for a simple low-risk reconstitution, common maximums are 48 hours at controlled room temperature and 14 days at 2–8 °C, though each facility must verify its own compatibility and stability. The terminal product is a patient-specific or office-use sterile injection, usually in a labelled syringe or overwrapped sterile vial.

Veterinary Oestrus Synchronisation: Dose Normalisation Across Mammalian Species

Chorionic gonadotrophin is used in veterinary reproduction to induce ovulation, correct follicular cysts, and support timed artificial insemination in cattle, mares, sows and small ruminants. Published veterinary formularies report a working range of 500 IU to 3,000 IU per animal, with the lower end used in sheep and the upper end in cattle and mares; the dose is normalised to species and reproductive indication rather than to a fixed mass fraction. The API is supplied as a sterile lyophilised powder, reconstituted with sterile water or sodium chloride injection before intramuscular or intravenous administration. Compliance for veterinary medicinal products in the European Union is governed by Regulation (EU) 2019/6, while the US Food and Drug Administration Center for Veterinary Medicine applies current good manufacturing practice under 21 CFR 211; sterility and bacterial endotoxin release are evaluated using USP <71> and USP <85> or corresponding Ph. Eur. methods. Unlike human single-use ART presentations, veterinary presentations may use larger multi-dose vials for herd-level protocols, and the stopper and diluent selection must reflect repeated reconstitution under farm conditions rather than pharmacy-controlled aseptic handling. Terminal product type: sterile veterinary powder for injection.

In freshwater and marine hatchery operations, chorionic gonadotrophin is used to synchronise final oocyte maturation and spawning in species that do not readily release gametes under routine culture conditions. Hatchery protocols reported in the applied aquaculture literature commonly use 500 IU/kg to 4,000 IU/kg body weight for females, often divided into two injections spaced 12–24 hours apart, with male fish receiving a lower dose or a single priming dose; the wide range reflects differences in species, water temperature, and gonadal maturation stage. The lyophilised API is reconstituted in sterile 0.9% sodium chloride injection and administered by intraperitoneal or intramuscular injection using fine-gauge syringes. Regulatory oversight is jurisdiction-specific: in many aquaculture-producing countries, the product enters through veterinary drug import licensing or national hatchery treatment authorisations, and in the EU any veterinary use falls under Regulation (EU) 2019/6, though a harmonised monograph for fish spawning induction does not exist. The terminal product is an injectable spawning aid packaged in small single-hatchery-use vials, not a food-animal growth promotant.

When Preservative-Free Single-Dose Vials Are Compelled by the Paediatric Cryptorchidism Indication

Preservative-free single-dose presentations are required for prepubertal cryptorchidism because multi-dose diluents containing benzyl alcohol are associated with serious adverse effects in neonates and infants. The vial label claim remains 5,000 IU or 10,000 IU, but the administered dose is an aliquot determined by body weight and clinical protocol; the prescriber directs the precise number of international units to be withdrawn from the reconstituted vial. Manufacture of this presentation follows the same aseptic lyophilisation route as other human injectables, but the release specification places additional emphasis on stopper extractables and leachables, subvisible particulate load under USP <788>, and clarity upon reconstitution. Production-scale experience shows that small-volume paediatric presentations are more sensitive to fill weight variability during lyophilisation, and the filling line must control fill accuracy within a narrow gravimetric window to avoid ambiguity when only a fraction of the vial is administered. Terminal product type: preservative-free single-dose sterile lyophilised powder for intramuscular injection.