Amoxicillin com/micro Pharma Grade API is a compacted or micronized presentation of amoxicillin trihydrate, a β-lactam antibacterial active pharmaceutical ingredient for oral tablet, capsule, granule, and suspension manufacturing, with a separate sterile sodium salt presentation for injectable compounding. The trihydrate entity has molecular formula C16H19N3O5S·3H2O, molecular weight 419.45 g/mol, and CAS 61336-70-7; the injectable sodium salt has CAS 34642-77-8. The com/micro designation does not identify a new chemical entity. It identifies particle-size architecture and bulk-handling performance. Compacted grade is densified for direct compression and dry granulation; micronized grade is size-reduced for high-surface-area aqueous dispersion and low-shear blending. The API is controlled against Ph. Eur. 0260, USP Amoxicillin Trihydrate, and JP Amoxicillin Hydrate monographs. Model identifiers such as AMX-C-100 and AMX-M-90 are manufacturer-assigned and are not harmonized across suppliers.

Manufacturing use spans oral solid-dose and sterile parenteral lines. The trihydrate form is processed into tablets, capsules, granules, and powder for oral suspension. The sodium salt is processed by aseptic dissolution, sterile filtration, and filling or lyophilization. The two presentations are not interchangeable without formulation adjustments because they differ in water content, pH, solubility, and sodium ion content.

What Separates Compacted from Micronized Amoxicillin Trihydrate in Solid-Dose Processing?

Particle-size distribution is the primary physical difference and is controlled by laser diffraction according to USP <429>. The compacted grade typically targets a median particle size D50 between 120 µm and 250 µm with a D90 not exceeding 700 µm; the micronized grade targets a D50 of 5–15 µm and a D90 of ≤20 µm. These values are representative manufacturer acceptance ranges and may differ between API suppliers. The compacted grade has a bulk density of 0.55–0.75 g/mL and a Carr index below 20, which permits consistent tablet weight control on rotary tablet presses running above 60,000 tablets/h. The micronized grade has a bulk density of 0.25–0.45 g/mL and is prone to rathole formation in bin discharge systems unless mechanical agitation, aeration, or vibratory hoppers are used.

Dry granulation via roller compaction operates with roll force control from 5 kN/cm to 15 kN/cm and roll gap of 1.5–2.5 mm to convert micronized powder into granules without removing the crystal water lattice. Published data for this specific configuration is limited, but comparable β-lactam roller-compaction studies indicate that excessive roll force increases granule hardness and reduces final compactibility. The compacted com/micro grade is therefore specified for direct compression formulations with drug loads above 70% w/w where flow segregation is a risk. Micronized grade is used when content uniformity must be achieved by high surface area and when low-dose granulation requires geometric dilution.

High-shear wet granulation of amoxicillin trihydrate requires a granulating fluid pH below 6.0 because alkaline conditions accelerate β-lactam ring opening to amoxicilloic acid. A granulating fluid at pH 4.5–5.5 prepared with purified water at 20–25°C is used; impeller tip speed is maintained at 5–8 m/s and wet massing time is not more than 3 min to limit capping and binder migration. Fluid-bed drying with inlet air at 40–50°C and product temperature not exceeding 35°C preserves the trihydrate crystalline water. Drying to water content below 11.5% can generate partially dehydrated material with altered dissolution and reduced stability. For tablet compression, compacted amoxicillin trihydrate is blended with microcrystalline cellulose, crospovidone, and magnesium stearate. Tablets compressed on a rotary press at 40–70 kN compression force for a 16×8 mm oval punch set exhibit hardness 80–120 N and friability below 1.0% according to USP <1216>. Disintegration is tested by USP <701>; for immediate-release amoxicillin tablets, disintegration typically occurs in less than 15 min.

For capsule filling, micronized amoxicillin is preblended with lactose monohydrate or mannitol and then filled on a dosator or tamping-pin capsule machine. Fill weight variation is controlled by powder bed height and machine speed; tamping-pin settings should be optimized to avoid overcompression and retarding dissolution. The micronized grade's higher specific surface area can increase moisture uptake; capsule shells should be stored at <25°C and <45% RH before filling to prevent brittle fracture.

Impurity Profiles and Residual Solvent Boundaries in Compendial Release Testing

Release testing follows the HPLC methods of Ph. Eur. 0260 and USP Amoxicillin Trihydrate. Total amoxicillin-related substances are maintained at ≤1.0%, and unspecified individual impurities are controlled at ≤0.10%. N,N-dimethylaniline, a potential process residual from the penam synthesis, is controlled at ≤20 ppm by gas chromatography according to Ph. Eur. 2.4.26. Water content by Karl Fischer titration per Ph. Eur. 2.5.12 is maintained at 11.5–14.5% for the trihydrate grade. Assay on the anhydrous basis is 95.0–102.0%. The suspension pH remains between 3.5 and 5.5 per Ph. Eur. 2.2.3. Residual solvents are controlled by Ph. Eur. 2.4.24 and USP <467> with limits assigned to the actual solvent class.

For oral suspension unit-dose sachets, sieved granule fractions are typically controlled between 180 µm and 710 µm. Fine material below 180 µm is limited to avoid dusting and content uniformity failures during sachet filling. Granule flow is measured by Hausner ratio; a Hausner ratio below 1.25 is preferred for volumetric sachet filling. Filling equipment operating at 60–100 sachets/min requires granule density stability. Micronized API is preblended with a hydrophilic diluent and then granulated with a binder solution to prevent API agglomeration. This grade is also used in powder for oral suspension because the high surface area reduces the time to reconstitute to a uniform suspension when the dry powder is mixed with water by the patient or caregiver.

When Amoxicillin Sodium Sterile Grade Replaces Trihydrate in Aseptic Filling Lines

The sterile sodium salt differs from the trihydrate in solubility, pH, and sodium load. It is dissolved in Water for Injection at 20–25°C to avoid heat-induced degradation. The bulk solution is filtered through a 0.22 µm sterilizing-grade polyvinylidene difluoride or polyethersulfone membrane before filling. Holding time of the sterile bulk solution is validated for pH drift, impurity formation, and bioburden. Formulation is performed in Grade C, corresponding to ISO 14644-1 ISO 7, and filling in Grade A, corresponding to ISO 5, under EU GMP Annex 1. Endotoxin control uses limulus amebocyte lysate testing per Ph. Eur. 2.6.14 or USP <85>. Sterility is confirmed by membrane filtration per Ph. Eur. 2.6.1 or USP <71>. Subvisible particles are controlled by light obscuration per USP <788> and Ph. Eur. 2.9.19 with limits matched to the finished injectable presentation.

The injectable sodium salt is not a direct substitute for oral trihydrate in dry powder processes because it lacks the stabilizing trihydrate water lattice and contributes sodium ions that alter isotonicity. pH of the reconstituted solution is controlled within 8.0–10.0 for a 10% solution, which is alkaline enough to accelerate hydrolytic degradation if held too long. Nitrogen overlay during filling reduces oxidative color formation. Lyophilized presentations require a validated cycle; collapse temperature and eutectic melting data are established by differential scanning calorimetry and freeze-drying microscopy. Moisture-stressed sodium salt should not be used without retest because hydrolytic degradation changes pH on reconstitution and may increase visible particle counts.

Relative to non-micronized amoxicillin trihydrate, the micronized com/micro grade provides a larger specific surface area and faster dispersion in aqueous media but generates more dust and requires stronger electrostatic control. Relative to amoxicillin sodium injectable grade, the trihydrate has low aqueous solubility and is unsuitable for intravenous solution without chemical conversion. Relative to co-processed amoxicillin and clavulanate potassium powders, the com/micro grade is a single-entity API; it does not contain moisture-sensitive clavulanate potassium, which normally requires separate granulation streams and low-humidity handling at <30% RH. These differences determine equipment selection, cleaning procedures, and storage conditions in multiproduct facilities.

β-Lactam Inactivation Requires Alkaline Cleaning at Defined Temperatures

Cross-contamination control in shared oral antibiotic facilities requires a maximum allowable carryover derived from the permitted daily exposure of the active and the minimum cleaned batch. Stainless steel 316L contact surfaces are washed with warm Water for Injection followed by 1% sodium hydroxide at 60–70°C for β-lactam ring hydrolysis, then rinsed to conductivity <1.3 µS/cm. High-performance liquid chromatography swab limits are set from the total organic carbon and specific amoxicillin residues. The analytical method should achieve a limit of quantification no greater than 50% of the acceptance swab limit. Dedicated or campaign production is required where β-lactam cross-contamination cannot be controlled below the threshold. Facility cleaning procedures should comply with 21 CFR 211.67 and the relevant Good Manufacturing Practice guidance for β-lactam antibiotics.

Powder transfer of micronized grade uses HEPA-filtered vacuum transfer with capture velocity 0.5–1.0 m/s to reduce airborne API. Operators handling powdered β-lactams should use isolator or split-valve transfer to avoid cross-contact and sensitization. The compacted grade produces less dust but can still generate fines during pneumatic conveying; the conveying system should use dilute-phase transport with a product velocity below 15 m/s to limit particle attrition.

Storage and transport conditions are assigned to preserve the trihydrate crystal water. The API is packaged in double low-density polyethylene liners inside a sealed aluminium-laminated bag under nitrogen. Recommended storage is 20–25°C with relative humidity <40%; exposure to relative humidity above 60% can cause micronized powder caking and flow decay. The trihydrate must not be stored above 30°C for prolonged periods or dried below its hydration water content. Retest intervals are based on long-term and accelerated stability studies per ICH Q1A(R2). Temperature dataloggers are used for sea freight in tropical zones. Material that has undergone temperature excursion outside labeled storage conditions is quarantined and tested before release for tableting or sterile compounding. Water content, impurity profile, and particle-size distribution are repeated after such excursions because caking and hydrate redistribution can change downstream processing behavior.