Designated as CILOSTAN (Cilostazol) CR Tab. Pharma Grade API, the product is supplied as a crystalline cilostazol base powder with a controlled particle-size distribution and pharmacopoeial-grade purity for use in oral solid dosage forms and, after additional bioburden and endotoxin controls, in injectable formulation development. Cilostazol is a selective phosphodiesterase III inhibitor; inhibition of cyclic adenosine monophosphate degradation in platelets and vascular smooth muscle produces antiplatelet and vasodilatory effects without clinically significant positive inotropy at the approved oral dose of 100 mg twice daily. The CR Tab. designation identifies a milled and sieved grade intended for controlled-release matrix tablets, capsules, and granules, with the base form rather than a salt or co-crystal. The API is tested against USP/NF and Ph.Eur. monographs, and batch release includes assay, related substances, residual solvents, elemental impurities, loss on drying, residue on ignition, particle size, bulk and tapped density, and X-ray powder diffraction. The product is packaged in double low-density polyethylene bags inside a fiber drum containing desiccant and is assigned a retest period of 36 months when stored below 25 °C and 60% relative humidity. The as-supplied API is non-sterile and is not terminally sterilized; injectable manufacturing sites must apply subsequent sterile filtration, aseptic processing, or terminal sterilization after formulation.

What Processing Window Does the CR Tab. Grade Require for Direct Compression?

Direct compression of CILOSTAN (Cilostazol) CR Tab. Pharma Grade API on a rotary tablet press with B-tooling operated at 40–80 rpm requires defined particle-size and flow inputs. The particle-size distribution is controlled to D50 15–30 µm and D90 ≤45 µm by laser diffraction on a Malvern Mastersizer 3000 with dry dispersion at 1 bar. Bulk density is held at 0.35–0.55 g/mL and tapped density at 0.45–0.65 g/mL by USP <616> Method I and II. These inputs support a Carr index of 15–22 and a Hausner ratio of 1.10–1.30, which reduce die-fill variability without wet granulation. In a representative direct-compression matrix containing microcrystalline cellulose PH-102, lactose monohydrate 100 mesh, pregelatinized starch, croscarmellose sodium, and magnesium stearate, the API is pre-blended for 10 min at 15 rpm in a bin blender; magnesium stearate is added at 0.5–1.0 wt% and mixed for 3 min to avoid over-lubrication. Compression force between 8 kN and 15 kN produces tablets with hardness 60–100 N and friability below 1.0% when tested according to USP <1216>. Content uniformity at 20–30 kg batch scale meets USP <905> acceptance criteria when the API is not exposed to relative humidity above 60% during hopper residence. In transfer runs on a 19-station rotary press, batch-to-batch variance in tablet hardness remained within ±5 N when the API D90 was held below 45 µm. The controlled-release matrix performance depends on the hydrophilic polymer grade; in hypromellose matrices, the release profile is qualified by USP <711> Apparatus II at 50 rpm in 900 mL of pH 6.8 phosphate buffer, with acceptance criteria set by the finished-product marketing authorization and not by the API alone.

For oral capsule and granule operations, the CR Tab. grade is compatible with roller compaction and high-shear wet granulation. Roller compaction on a Gerteis Mini-Pactor at roll force 4–8 kN/cm and gap 1–2 mm yields ribbons with density 0.9–1.1 g/cm³; subsequent milling through a 0.8 mm screen produces granules suitable for capsule filling on an MG2 Planeta or equivalent dosator machine. Granulation with water or an aqueous binder solution requires the API to be pre-dried at 40 °C for 2 h if loss on drying exceeds 0.5%, because residual moisture above 0.8% promotes agglomeration and retards dissolution in hypromellose-based matrices. Capsule filling of the API without granulation is limited by its low bulk density and cohesive fines; if capsule filling is attempted, a minimum of 25–30% diluent premix by weight is recommended to maintain fill-weight uniformity.

Specification Profile and Pharmacopoeial Monograph Methods

Release of CILOSTAN (Cilostazol) CR Tab. Pharma Grade API is controlled under ICH Q7 and EU GMP Part II. The following specification profile applies to the oral grade; injectable-grade material adds the endotoxin and particulate controls listed separately.

When an injectable presentation is developed, transfer of the API from oral grade to injection grade introduces controls not required for solid oral dosage forms. The base has aqueous solubility below 0.01 mg/mL at 25 °C; therefore a solubilizing system containing a cyclodextrin derivative, a co-solvent such as polyethylene glycol 300 or propylene glycol, or a lipid emulsion is needed before sterile filtration. The API as supplied is non-sterile; the formulated product must be passed through a sterilizing-grade filter, typically 0.22 µm polyvinylidene fluoride or polyethersulfone, and filled aseptically. Pre-filtration bioburden should be controlled below 10 CFU/100 mL to comply with current EU GMP Annex 1 expectations. Bacterial endotoxin limits for the API are set at <0.5 EU/mg when the material is intended for parenteral screening, but finished-product endotoxin limits must be justified by the maximum daily dose and route. Particulate matter in the finished injection is tested according to USP <788> or Ph.Eur. 2.9.19; visible and subvisible particle counts are formulation-dependent. Because terminal sterilization by moist heat may alter the polymorph stability and dissolution behavior of cilostazol, the preferred manufacturing route is aseptic filtration of a solubilized form; published data on terminal sterilization of this specific injectable configuration is limited.

If Terminal Sterilization Is Considered, What Limitations Apply to the API?

If terminal sterilization of a CILOSTAN (Cilostazol) CR Tab. Pharma Grade API-containing parenteral product is considered, the thermal exposure should be limited to 121 °C for 15 min only after confirming that the formulation does not show polymorphic conversion or release of the API from the drug product matrix. Cilostazol base has a melting point near 159–160 °C; however, exposure to moist heat in the presence of water can accelerate hydrolysis of the amide bond and generate related substances that are controlled at ≤0.5% in the oral API specification. Steam sterilization of dry API powder is not recommended because the bulk powder may be heat-labile and surface moisture can cause caking and changes in particle-size distribution. If terminal sterilization is unavoidable, the formulated solution should be sparged with nitrogen and the headspace oxygen content maintained below 2% to reduce oxidative degradation. Sterilization validation would require demonstration of a sterility assurance level of 10^-6 according to ISO 14937 or USP <1229>, with endotoxin and particulate limits reconfirmed after the sterilization cycle.

The CR Tab. Grade Addresses Segregation and Flow Failures in High-Speed Compression

Compared with conventional unmilled cilostazol API, CILOSTAN (Cilostazol) CR Tab. Pharma Grade API reduces segregation in low-dose direct-compression blends. A conventional API lot may exhibit a broad particle-size distribution with D50 values between 40 µm and 100 µm and D90 values above 200 µm, which increases the risk of content uniformity failures under high-speed compression above 60 rpm. The CR Tab. grade maintains a tight span of 1.5–2.5 and removes oversize particles through a 325 mesh or 45 µm sieve, improving batch-to-batch consistency. Unlike a simple micronized powder, which may improve dissolution but worsen flow and increase electrostatic adhesion, the CR Tab. grade balances size reduction with bulk density to maintain die-fill consistency. Against other PDE3 inhibitor APIs such as milrinone and inamrinone, cilostazol base offers a distinct pharmacological profile: antiplatelet and vasodilatory activity with lower risk of positive inotropy at the approved dose. The controlled-release tablet grade is not a salt, so pH-dependent solubility must be considered in matrix selection; enteric or pH-modifying excipients may be required if the formulation targets pH-independent release. Published data for the comparative tableting performance of this specific grade against other suppliers’ cilostazol APIs is limited; the following representative preformulation data illustrate the observed differences.

For warehousing and dispensing, the API should be handled according to ICH Q1A and the supplier’s retest statement. The material is stored in double polyethylene bags with desiccant at or below 25 °C and 60% relative humidity. Prolonged exposure to relative humidity above 60% during hopper residence should be avoided because caking can increase particle agglomeration and require re-milling. Contact with strong oxidizing agents and highly acidic or alkaline aqueous media should be avoided during formulation, because cilostazol base undergoes pH-dependent degradation. Wet granulation contact surfaces should be stainless steel 316L or higher; uncoated steel surfaces are not recommended. The as-supplied API is not sterile and must be handled as a chemical intermediate under local occupational exposure limits.