Amifostine for Injection Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable is released as S-2-(3-aminopropylamino)ethyl dihydrogen phosphorothioate trihydrate, molecular weight 268.27 g/mol. The manufacturer’s grade designation is AFI-500-LYO for lyophilization-compatible API; a non-sterile solid-dosage grade is available for tablet, capsule, and granule feasibility studies. The product is a white or almost white crystalline powder controlled to USP–NF and Ph. Eur. monograph criteria for parenteral-grade amifostine; batch release includes identity, assay, water content, related substances, residual solvents, elemental impurities, and bacterial endotoxins. The crystalline trihydrate form carries a theoretical water content of 20.1%; lyophilization-grade material is conditioned for aseptic processing into sterile vials, while the same active compound can be classified for non-sterile oral processes after particle-size and excipient-compatibility confirmation. The injectable route is the only dosage pathway with established regulatory history; oral and granule presentations are non-compendial and require separate formulation justification.

Packaging for injectable-grade material consists of double low-density polyethylene liners within a sealed aluminum-laminate drum; desiccant is excluded to avoid stripping the crystalline water. Inventory should be held at 2–8 °C and protected from moisture; repeated warming to ambient temperature should be limited because condensation on the powder surface raises local water activity and accelerates hydrolysis.

Why Does Alkaline Phosphatase Activation Separate Amifostine from Other Thiol-Based Cytoprotectants?

In plasma and tissue, amifostine functions as a prodrug; membrane-bound alkaline phosphatase cleaves the phosphate group to release the free thiol WR-1065. This activation step distinguishes amifostine from mesna, which circulates as sodium 2-mercaptoethanesulfonate and does not require phosphate cleavage, and from dexrazoxane, which acts primarily through iron chelation rather than sulfhydryl donation. The consequence for manufacturing is that the phosphorothioate ester and free thiol must be protected from acid-catalyzed hydrolysis and oxidative dimerization before administration; thiol-disulfide interconversion is accelerated when solution pH falls below 6.0 or rises above 7.5. Injectable compounding with sterile water for injection to a concentration of 50 mg/mL yields a reference solution pH of 6.5–7.5; further dilution with 0.9% sodium chloride injection is performed immediately before intravenous infusion. In oral tablet or capsule formulations, the activation pathway becomes a formulation barrier because alkaline phosphatase is not uniformly available in the gastrointestinal lumen; published pharmacokinetic data for oral modified-release amifostine remain limited, and no compendial dissolution method exists for this application.

Batch-release specifications for parenteral-grade amifostine API are structured around identity, purity, and process-safety thresholds. The following control matrix aligns with current pharmacopoeial monograph expectations; acceptance limits should be confirmed against the exact edition cited in the regulatory submission.

The calculated endotoxin limit is derived from the general formula K/M, where K is 5 EU/kg and M is the maximum parenteral dose of 7.14 mg/kg for a 500 mg dose in a 70 kg adult. Injectable-grade suppliers typically apply a tighter in-house bioburden limit before sterile filtration.

Beyond the release table, the trihydrate crystal form should be confirmed by X-ray powder diffraction because partial dehydration to an anhydrous or amorphous form can occur during unprotected drying. Storage at 2–8 °C in a dry-nitrogen environment preserves the crystalline water; exposure to relative humidity above 60% RH at dispensing stations has been associated with surface clumping and reduced flow through rotary tablet presses. Loss on drying is therefore not interchangeable with Karl Fischer water content for this API; thermogravimetric analysis may over-report water if the heating ramp drives off the trihydrate water before decomposition.

When Bulk Solution Temperature Exceeds 5 °C During Sterile Filtration

Parenteral compounding of amifostine requires cold-chain control because oxidative degradation of the reconstituted solution becomes measurable when bulk holding exceeds 5 °C for more than 8 h. Jacketed stainless-steel vessels with recirculating coolant at 2–5 °C are used to hold the bulk solution after dissolution; dissolved oxygen is displaced with nitrogen until headspace oxygen remains below 1%. Terminal steam sterilization at 121 °C is not applicable because the phosphorothioate ester and free thiol degrade under superheated aqueous conditions; aseptic filtration through a 0.22 μm polyvinylidene fluoride or polyethersulfone membrane is the established manufacturing sequence. Filter integrity testing is performed before and after filtration in accordance with ISO 13408-2. Product-wet filter validation should assess extractables and leachables per USP <1663> and USP <1664>.

The filtered solution is filled into 50 mL Type I glass vials and lyophilized. During cycle development, freeze-drying microscopy is used to determine the collapse temperature; published collapse-temperature data for this specific formulation are limited, so the primary drying shelf temperature should be held below the measured collapse midpoint and chamber pressure should be controlled at 0.05–0.15 mbar during sublimation. Production-scale lyophilizers with non-uniform shelf heating show increased residual-moisture variance when vial load density exceeds 0.8 vials/cm²; this behavior has been observed as longer reconstitution times and should be addressed by load-pattern qualification. Compounding and filling occur in a Grade A unidirectional airflow zone with a Grade B background as defined by EU GMP Annex 1 and ISO 14644-1; Grade A limits for particles ≥0.5 μm are 3,520 particles/m³ in operation. Reconstituted vials held at room temperature are typically used within 24 h; the exact stability window must be taken from the finished-product label and not from API stability data.

For tablet, capsule, and granule dosage forms, the API particle-size distribution must be matched to blend uniformity rather than dissolution alone. Direct compression and dry granulation are generally safer than aqueous wet granulation because prolonged contact with acidic or alkaline granulating fluids accelerates disulfide dimer formation and reduces assay. If wet granulation is unavoidable, the granulating liquid should be prechilled to 2–8 °C and the drying inlet temperature should be kept below 40 °C to limit thermal oxidation and crystal water loss. Roller-compacted granules intended for hard gelatin capsules should be tested according to USP <711> for dissolution, USP <701> for disintegration, and USP <905> for content uniformity; because no compendial oral dissolution monograph exists for amifostine, the acceptance criterion must be derived from phase-appropriate clinical data. Tablet formulations containing peroxidic crospovidone or povidone should be avoided or controlled with antioxidant stabilizers; the thiol group is incompatible with strong oxidizing agents and heavy-metal catalysts. Hard gelatin capsule fill operations should maintain relative humidity below 45% RH to prevent powder agglomeration on dosator or tamping-pin stations. Oral delivery of the free thiol remains a formulation challenge: amifostine is subject to presystemic degradation, and published data for enteric-coated, gastroretentive, or mucoadhesive amifostine systems are limited. Consequently, the injectable presentation remains the only dosage form with established clinical pharmacology.

Elemental Impurity and Residual Solvent Audit Controls

Multi-source amifostine API requires a documented supply-chain audit because final purification can introduce palladium or platinum residues if catalytic hydrogenation is used. ICH Q3D Option 1 is applied for parenteral products; for oral products, the same elemental impurity limits are often adopted to avoid dual specifications. Residual solvent testing by headspace gas chromatography is aligned with ICH Q3C; ethanol, methanol, and isopropyl alcohol are the most common process solvents that must be controlled. The certificate of analysis should include a nitrosamine risk evaluation according to ICH M7 and current WHO guidance; amifostine does not contain the typical secondary-amine nitrosation-prone group, but the evaluation must be documented. For non-sterile grades, total aerobic microbial count and total combined yeast and mold count are tested per USP <61> and USP <62>. For injectable-grade API, bioburden is additionally controlled before sterile filtration; a pre-filtration bioburden limit of ≤10 CFU/g is commonly applied in aseptic campaigns, with objectionable organisms absent.

Relative to mesna, which is formulated as a stable aqueous solution for injection and does not require lyophilization, amifostine trihydrate is more oxidation-sensitive and demands cold-chain compounding. Relative to dexrazoxane, which is supplied as a lyophilized product with a distinct iron-chelating mechanism, amifostine has a broader labeled indication for cisplatin-associated renal toxicity and radiation-induced xerostomia. The injectable dose is 910 mg/m² intravenously over 15 min before cisplatin chemotherapy, and 200 mg/m² intravenously over 3 min before radiation therapy, based on approved labeling; these doses must not be transferred to oral or granule dosage forms without separate pharmacokinetic justification. The API product is therefore positioned for lyophilized injection manufacture, while tablet/capsule/granule grades require additional particle engineering, stability, and dissolution development.