2′-Fluoro-2′-deoxyuridine, CAS 784-71-4, molecular formula C₉H₁₁FN₂O₅, relative molecular mass 246.19, is released under the model designation 2FdUrd-Ph-API for tablet, capsule, granule, and injectable manufacture. The material is a white to off-white crystalline powder. Identity is verified by infrared absorption spectrophotometry and HPLC retention time concordance against a qualified reference standard. The release specification includes assay by HPLC of 98.0% to 102.0% on the anhydrous basis, total related substances ≤ 1.0%, water content ≤ 0.5% w/w by Karl Fischer titration, residue on ignition ≤ 0.1%, and residual solvents controlled per ICH Q3C. Elemental impurities are controlled per ICH Q3D for oral and parenteral routes; ICP-MS is used after microwave-assisted acid digestion.

The compound is a positional isomer of 5-fluoro-2′-deoxyuridine; both share the molecular formula C₉H₁₁FN₂O₅ but differ in the attachment position of the fluorine atom. In the present material, the fluorine is located at the 2′ position of the deoxyribose ring, whereas in floxuridine the fluorine is located at the 5 position of the uracil base. This distinction changes the infrared C–F stretching region, the reversed-phase HPLC retention time, and the acid-hydrolysis profile. The solid is packaged in double low-density polyethylene bags inside aluminum-laminated drums and stored at 2–8 °C with desiccant.

For oral solid-dose processing, the API is blended with microcrystalline cellulose and lactose monohydrate meeting current Ph. Eur. excipient monographs. Wet granulation is avoided unless a non-aqueous binder system is used, because the glycosidic bond is susceptible to acid-catalyzed hydrolysis. For injectable presentations, the API is dissolved in Water for Injections and lyophilized; the bulk solution is filtered through a 0.22 µm polyvinylidene fluoride membrane before filling. Published data for this specific configuration in finished oral dosage forms is limited; therefore, dissolution and bioavailability must be established by the finished-product manufacturer.

What limits direct compression of this API in low-dose oral solid dosage forms?

The direct compression window is governed by particle size distribution, moisture content, and powder flow. Laser diffraction data are generated according to ISO 13320:2020; the release specification requires D90 ≤ 150 µm for tableting grade and D90 ≤ 45 µm for injectable-grade micronized material. Bulk density and tapped density are measured per USP 616; the Carr index and Hausner ratio are calculated from those values. A batch with Carr index > 25 or Hausner ratio > 1.25 is not released for direct compression without dry granulation.

On a 10-station rotary tablet press operated at 15–25 rpm and compression force 8–15 kN, capping and lamination are observed when residual moisture exceeds 1.0% w/w and the granulate contains more than 20% fines below 75 µm. Pre-drying at 40 °C under vacuum until loss on drying ≤ 0.5% w/w is required when the processing area exceeds RH 60%. The API is blended in a V-shell blender at 25 rpm for 15 min; extended blending beyond 30 min increases electrostatic charge and reduces content uniformity.

When dry granulation is used, a roller compactor with roll pressure 20–40 bar and a 1.0 mm screen is operated. The resulting ribbons are milled and the granulate is compressed into tablets with hardness 5–8 kp; disintegration is tested per USP 701. Tablet dissolution is evaluated using USP Apparatus II at 50 rpm in 900 mL of 0.1 M hydrochloric acid.

When the API is designated for injectable lyophilization, endotoxin and subvisible particulate thresholds become release-limiting

Injectable grade requires bacterial endotoxin ≤ 0.5 EU/mg by Ph. Eur. 2.6.14. Subvisible particulate matter is tested per USP 788 after reconstitution of the lyophilized product; the limits are ≤ 6000 particles per container at ≥ 10 µm and ≤ 600 particles per container at ≥ 25 µm. The bulk solution is filtered through a 0.22 µm polyethersulfone membrane filter before lyophilization. Filter compatibility is confirmed by extractables and leachables profiling according to current regulatory guidance.

The lyophilization cycle uses a primary drying shelf temperature of −25 °C to −20 °C and chamber pressure 100–150 mTorr. The API is dissolved in Water for Injections at 20–25 °C; if the solution is held for more than 4 h before filtration, the parent peak area should be rechecked by HPLC because of potential glycosidic hydrolysis. The sterile grade is tested for sterility per Ph. Eur. 2.6.1; terminal steam sterilization is not used because heat and moisture accelerate degradation. The injectable grade is released only after lyophilizate cake appearance is confirmed as intact and the reconstituted solution meets clarity and pH specifications of 4.0–7.0.

Compendial release criteria and elemental impurity mapping

Chromatographic purity is determined using a reversed-phase C18 column with UV detection at 260 nm. The quantitation limit for specified impurities is 0.05% relative to the API peak. The XRPD measurement is performed over the 2θ range 3–40°; the three principal reflections must match the reference within ± 0.2° 2θ.

For granule-filled sachets, the API is dry-granulated with mannitol and crospovidone; the granulate is filled at a target weight of 500 mg per sachet with fill weight variation ≤ 5% RSD. The moisture barrier of the sachet laminate is specified at water vapour transmission rate ≤ 0.1 g/m²/day at 38 °C/90% RH per ASTM F1249. The finished granule is tested for dissolution using USP Apparatus II at 50 rpm in 900 mL of 0.1 M hydrochloric acid; acceptance is Q = 80% in 30 min for immediate release. Capsule formulations use size 3 hard gelatin capsules with lactose monohydrate and sodium starch glycolate; the blend is filled on a dosator-type capsule machine. The blend is not lubricated with magnesium stearate above 0.5% w/w because hydrophobic lubricant films reduce dissolution at low dose. The empty capsules meet the requirements of USP 711 and the finished capsules are stored in PVC/PVDC/aluminum blisters to limit moisture ingress.

The 2′-fluoro substitution is not analytically interchangeable with 5-fluorouracil or floxuridine

In 5-fluorouracil the fluorine atom is bonded to the uracil base at the 5 position; in floxuridine the same base modification is present with a 2′-deoxyribose sugar. The material described here carries fluorine at the 2′ position of the deoxyribose ring while the uracil base remains unsubstituted. This difference changes the infrared C–F stretching fingerprint, the reversed-phase HPLC retention time, and the susceptibility of the glycosidic bond to acid hydrolysis. The API should not be substituted by weight into a floxuridine or 5-fluorouracil formulation without re-development of the analytical method and process.

The API supplier does not establish therapeutic equivalence or bioequivalence. Substitution of this API into a marketed floxuridine or 5-fluorouracil drug product should not occur without appropriate regulatory variation, finished-product stability data, and comparative dissolution testing. The manufacturer is responsible for confirming that the final dosage form meets the finished-product monograph and the approved marketing authorization specification.