When spray-dried liposomal melatonin pharma grade API is selected for immediate-release tablet lines, the principal process conflict is the compaction pressure window that preserves vesicular integrity. A direct compression route is preferred over wet granulation because the aqueous binder addition and drying phases of wet granulation can cause multilamellar vesicle fusion in the absence of a rigid protective matrix. The liposomal powder is first passed through a 500 µm sieve and combined in a bin blender with microcrystalline cellulose, lactose monohydrate, croscarmellose sodium, and colloidal silicon dioxide at 15 rpm for 20 minutes. Magnesium stearate is added separately through a 250 µm sieve and blended for 3 minutes to limit over-lubrication. The final blend is compressed on a rotary tablet press equipped with B-tooling and 8 mm round concave punches; the pre-compression force is maintained between 4 kN and 6 kN, and the main compression force is held between 10 kN and 16 kN. Tablet hardness is controlled in the 50–80 N range, and friability is verified according to USP <1216>. The formulation addition ratio for a 200 mg core is: liposomal melatonin 2.0–10.0% w/w (equivalent to 1–5 mg melatonin per tablet), microcrystalline cellulose 45–65% w/w, lactose monohydrate 20–35% w/w, croscarmellose sodium 1.5–3.0% w/w, colloidal silicon dioxide 0.25–0.75% w/w, and magnesium stearate 0.5–1.0% w/w. Dissolution testing is performed under USP <711> Apparatus II at 75 rpm in 900 mL phosphate buffer at pH 6.8; release of melatonin at 30 minutes is a routine in-process checkpoint. Content uniformity is assessed by USP <905> with an acceptance value not exceeding 15. The terminal dosage form is either an uncoated immediate-release tablet or a film-coated tablet using a low-viscosity HPMC/PEG coating system applied at a 2.0–4.0% weight gain. Handling of the spray-dried liposomal API is restricted to ≤40% relative humidity and ≤25 °C; exposure above 40 °C softens the lipid excipients and increases the risk of agglomeration during sieve transfer.

Fluidised-Bed Pellet Coating for Extended-Release Liposomal Melatonin Capsules

Extended-release multi-particulate capsules exploit the ability of a cured ethylcellulose membrane to slow melatonin diffusion after oral administration. Sugar spheres of 250–355 µm are first charged to a Wurster HS fluid-bed system, and a layering dispersion containing liposomal melatonin pharma grade API, hydroxypropyl methylcellulose, and purified water is sprayed onto the spheres. The product bed temperature is maintained between 38 °C and 42 °C; inlet air temperature is set between 45 °C and 55 °C, atomising air pressure between 1.0 bar and 1.5 bar, and spray rate between 6 g/min/kg and 10 g/min/kg of substrate. Exceeding 42 °C product temperature produces visible pellet agglomeration in the Wurster partition and shifts the liposomal particle size distribution above 500 nm. Melatonin loading on the spheres is controlled at 0.5–5.0% w/w of the layered pellet mass, enabling fill weights that deliver 1–10 mg melatonin per capsule. The sustained-release coating is an aqueous ethylcellulose dispersion applied to a weight gain of 8–15% w/w. After coating, pellets are cured at 50–60 °C for 2 hours to complete film coalescence. Cured pellets are filled into hard HPMC capsules using an automatic capsule filler with pellet fill weight checked by USP <905> content uniformity. Dissolution is run under USP <711> Apparatus I at 100 rpm in 500 mL simulated gastric fluid for the first 2 hours, followed by simulated intestinal fluid pH 6.8 for the remaining intervals. Stability is assessed under ICH Q1A(R2) at 25 °C/60% RH and 30 °C/65% RH; release rate shifts greater than 5% at the 4-hour sample point are considered out-of-trend. The terminal dosage form is a two-piece HPMC extended-release capsule.

Granulation for single-dose paediatric sachets proceeds from a pre-blend of spray-dried liposomal melatonin, mannitol, pregelatinised starch, and sodium croscarmellose. The powder mixture is granulated in a high-shear wet granulator using purified water as the binder at an impeller speed of 150–250 rpm and a chopper speed of 800–1200 rpm; the wet mass is discharged through a 2.0 mm screen and dried in a fluid-bed dryer at an inlet temperature of 50–60 °C until loss on drying is below 2.0%. The dried granules are passed through an 800 µm oscillating sieve and filled into stick-pack sachets. The addition ratio places liposomal melatonin at 2.0–5.0% w/w of the final granule mass, with mannitol at 75–85% w/w, pregelatinised starch at 8–12% w/w, croscarmellose sodium at 1.0–3.0% w/w, and colloidal silicon dioxide at 0.25–0.50% w/w. Sachet fill weights of 500–2000 mg deliver 0.5–3 mg melatonin per unit. Uniformity of mass is verified under Ph. Eur. 2.9.5 with a maximum deviation of 7.5% for single-dose powder preparations; moisture content is controlled under Ph. Eur. 2.2.32. Powder flow is assessed by USP <1174>, with target compressibility index below 25% and Hausner ratio below 1.25. Microbial quality is tested under USP <61> and USP <62>. The terminal dosage form is a single-dose paediatric granule sachet intended for suspension in water or soft food.

When Lyophilised Liposomal Melatonin Is Reconstituted in Sterile Water for Injection

For aseptic production of lyophilised injectable liposomal melatonin pharma grade API, the lipid phase is prepared from hydrogenated soy phosphatidylcholine and cholesterol in a defined molar ratio; the lipid-to-melatonin molar ratio is maintained between 10:1 and 20:1 to ensure measurable encapsulation efficiency above 85% after extrusion. The phospholipid concentration before lyophilisation is typically 20–50 mg/mL, and the aqueous phase contains trehalose or sucrose at 5–10% w/v as the lyoprotectant. The coarse dispersion is processed through high-pressure homogenisation at 8,000–12,000 psi for 5–10 discrete passes until the Z-average particle size is below 100 nm and polydispersity index below 0.200; aseptic filtration through a 0.22 µm sterilising-grade membrane follows before filling into depyrogenated Type I glass vials. The lyophilisation cycle freezes the filled vials at -40 °C to -50 °C, holds primary drying at -20 °C and 50 Pa, and elevates secondary drying to 25 °C and 10 Pa until residual moisture is below 1.0%. After reconstitution in 5 mL sterile water for injection, the product delivers 0.5–2 mg/mL melatonin. Sterility is assessed by USP <71>; bacterial endotoxins are controlled under USP <85> with a limit of ≤2.0 EU/mg or ≤2.0 EU/mL after reconstitution, depending on the registered specification. Subvisible particulate matter is limited by USP <788> to not more than 6000 particles per container at ≥10 µm and not more than 600 particles per container at ≥25 µm. Liposome-specific particle size distribution and encapsulation efficiency are monitored using dynamic light scattering and centrifugal ultrafiltration; no single-dilution pass/fail criterion is substituted for batch trend review. The terminal dosage form is a sterile lyophilised powder for injection or infusion after reconstitution.

What Limits Sedimentation in Aqueous Liposomal Melatonin Suspensions?

Sedimentation in aqueous oral suspensions is controlled by reducing liposomal particle size, adjusting continuous-phase viscosity, and selecting preservatives that do not induce vesicle aggregation. The liposomal melatonin concentrate is diluted into a vehicle containing glycerin, xanthan gum, and purified water; the batch is passed through a high-pressure homogeniser at 8,000–12,000 psi to lower the Z-average particle size to 100–200 nm. Xanthan gum is dispersed at 0.2–0.5% w/v to generate a low-shear viscosity of 50–150 mPa·s at 25 °C, sufficient to reduce creaming without producing a highly pseudoplastic mouthfeel. The addition ratio in the final suspension is 0.1–1.0 mg/mL melatonin, liposomal lipid 5–20 mg/mL, glycerin 15% w/v, and sodium benzoate 0.1% w/v. Microbial quality is evaluated by USP <61> for total aerobic microbial count ≤10² CFU/mL and total combined yeasts and moulds ≤10¹ CFU/mL; USP <51> preservative efficacy testing is required for multi-dose containers. The terminal dosage form is an oral suspension or drop liquid packaged in amber glass bottles with a calibrated dropper.

Orodispersible Lyophilisates Are Affected by Freeze-Drying Parameters

Orodispersible liposomal melatonin dose units are produced by freeze-drying a metered aqueous dispersion directly in blister pockets. The dispersions contain gelatin at 2–5% w/w as the matrix former, mannitol at 3–6% w/w as the crystalline bulking agent, and liposomal melatonin pharma grade API at 5–15% w/w of the total wet mass. The liquid is dosed at 0.5–1.0 mL per pocket and frozen at -40 °C to -50 °C before primary drying at -20 °C and 50 Pa. Secondary drying at 25 °C and 10 Pa reduces residual moisture below 1.5%. Disintegration is tested under USP <701> with a limit of ≤30 seconds in 37 °C water; content uniformity is confirmed by USP <905>. The terminal dosage form is an oro-dispersible lyophilisate for sublingual or buccal absorption, packaged in peel-off blister lidding with desiccant protection.