Liposomal Magnesium Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable is released under two route-specific model designations: LMG-PG-API-F70 for oral solid and granule manufacture and LMG-PG-API-PA for sterile injectable compounding or infusion. The dry oral grade is a spray-dried phospholipid vesicle powder, while the parenteral grade is supplied as a lyophilized cake or concentrated aqueous dispersion. The encapsulated salt is magnesium sulfate heptahydrate within a bilayer of hydrogenated soy phosphatidylcholine and cholesterol; the unencapsulated fraction is controlled separately because it determines the immediate-release behavior of the finished dose. The vesicle population exhibits a D50 of 100–250 nm for oral material and 80–150 nm for parenteral material after rehydration, measured by dynamic light scattering per ISO 22412:2017. Elemental magnesium content is 6.5–8.5 % w/w for oral powder and 5.5–7.5 % w/w for parenteral lyophilizate by Ph. Eur. 2.2.57 ICP-OES. The term “pharma grade” denotes compliance with compendial impurity, microbiological, and elemental limits rather than a single chemical identity.

Release Specifications and Compendial Method Mapping

The two model designations differ primarily in sterility, endotoxin limit, and particle size, not in core bilayer composition. The release panel is mapped to compendial methods and includes both physicochemical and microbiological endpoints. Representative batch data are shown in the table below.

The oral grade is not terminally sterilized and is therefore assigned only to non-sterile dosage forms. The parenteral grade is released only after sterility and endotoxin testing, and after reconstitution it must meet the particulate matter criteria in USP <788> and USP <790> according to the route of administration.

What Changes During Liquid Dispersion and Sterile Filtration of the Parenteral Grade?

Reconstitution of LMG-PG-API-PA to 20 mg/mL elemental magnesium produces a translucent dispersion with pH 6.5–7.5. Terminal sterilization by moist steam is constrained by the main phase transition of hydrogenated soy phosphatidylcholine, typically 52–55 °C; autoclaving above this range drives vesicle fusion and particle growth beyond the 0.2 µm filtration track. Filtration through a 0.2 µm polyethersulfone membrane is feasible when the reconstituted D90 remains below 180 nm. If the D90 exceeds 220 nm, membrane blinding is observed and the pressure differential can exceed 1.5 bar within 20 min at 25 °C. Isotonicity adjustment with sodium chloride to 280–320 mOsm/kg is performed after active loading because free magnesium competes with sodium during dilution. The aseptic compounding window is 4 h at 2–8 °C after first breach of the lyophilized container; beyond this window, microbial outgrowth risk must be managed by sterile filtration rather than by preservatives, and the dispersion should be discarded if it is not processed through a validated 0.2 µm sterilizing filter.

High-shear wet granulation is generally not the primary route for LMG-PG-API-F70 because an aqueous phase induces phospholipid hydrolysis and increases the free magnesium fraction. Dry granulation is preferred. On a 150 L high-shear granulator used only for preblending, chopper speeds above 1000 rpm have decreased encapsulation efficiency in production batch records from 72 % to 48 % when product temperature exceeded 45 °C for more than 30 min. Tablet compression on a rotary press with 12 mm round tooling at 60–120 MPa produces tensile strength 1.8–2.6 MPa and friability below 0.8 % per USP <1216>, provided the external lubricant phase contains not more than 0.5 % w/w magnesium stearate. Higher lubricant levels reduce tensile strength and increase disintegration time beyond 30 min in USP <701> testing. Capsule filling requires conditioning at 35–40 % RH and 20–25 °C for 24 h before filling; mass uniformity remains below 2 % RSD on dosator-type equipment under these conditions.

If Roller Compaction Exceeds 18 kN/cm, What Happens to Liposome Bilayer Integrity?

Ribbon density is the controlling parameter. Roll force above 18 kN/cm on an Alexanderwerk WP 120 roller compactor increases ribbon density beyond 1.25 g/cm³; the internal shear crushes a subpopulation of liposomes. Rehydrated granules from this condition show an increase in D90 from 340 nm to 780 nm, and encapsulation efficiency falls by 15–25 percentage points. Milling through a conical mill screen of 1.0 mm at 1200 rpm further shears the bilayer; screen sizes below 0.5 mm are outside the validated window because they reduce encapsulation efficiency below the oral release limit. Ribbons produced at 12–16 kN/cm and milled at 900–1100 rpm typically retain acceptable granule flow function with Carr index 18–24 % and rehydrated D90 below 400 nm. If dissolution release of the encapsulated fraction must exceed 80 % at 60 min in USP apparatus 4, the compaction step is the main risk control point. Where batch-to-batch variation exceeds the specified envelope, published data for this specific formulation configuration is limited and process qualification is required.

Differentiating This API from Unencapsulated Magnesium Sources

The principal difference between this API and free magnesium salts is not total magnesium content but the rate of appearance of ionic magnesium in aqueous media. Magnesium sulfate heptahydrate releases nearly all free magnesium within 10 min in water, whereas the liposomal dispersion retains at least 70 % of total magnesium in the vesicle compartment over the same interval under controlled agitation. This changes the osmotic effect of oral doses: a 300 mg elemental magnesium dose as magnesium sulfate produces an immediate osmotically active free-ion load, while the liposomal product partitions the same dose into a smaller initial free-ion fraction and a slower vesicle-associated release fraction. The comparison below summarizes the technical distinctions.

The liposomal form avoids the alkaline pH excursion associated with magnesium oxide slurries, which can exceed pH 10. It also reduces the rapid osmotic diarrhea signal commonly linked to unencapsulated soluble magnesium salts at high elemental doses, although clinical equivalence must be established by the finished-dose sponsor using the appropriate pharmacokinetic and tolerability endpoints.

Endotoxin, Particulate, and Residual Solvent Control in the Injectable-Grade Powder

Injectable-grade liposomal magnesium is controlled for endotoxin, particulate matter, and residual solvents as a system rather than as disconnected tests. The lyophilized cake must reconstitute to a dispersion free of visible particles and then meet the sub-visible particle limits in USP <788>. Endotoxin control begins with the phospholipid and magnesium salt source and is confirmed by Ph. Eur. 2.6.14; retesting after terminal filtration is appropriate because endotoxin may remain biologically active even if the filtration step removes viable organisms. Residual solvent control follows ICH Q3C with particular attention to ethanol, acetone, and chloroform if these solvents are used in the lipid dissolution step. The lyophilization cycle is designed to keep product temperature below the phospholipid phase transition during primary drying; a collapse temperature failure that produces a shrunken cake also produces vesicle aggregation and must be rejected before sterile release.

Operational boundaries for compounding and formulation include the following incompatibilities. The liposomal API should not be combined with anionic polysaccharides such as sodium carboxymethylcellulose at concentrations above 0.1 % w/w in aqueous dispersion because depletion flocculation increases D90 beyond 500 nm. Phosphate buffers above pH 7.5 should be avoided because free magnesium precipitates as magnesium phosphate, producing sub-visible particles measurable by USP <788>. For oral dry blends, do not pre-dry at temperatures above 40 °C when ambient RH exceeds 60 % because condensation during cooling can hydrate the bilayer and cause sticking on tablet tooling. The liposomal API is not a lubricant and must not be substituted for magnesium stearate in the external phase of a tablet formulation; its lipid content is 60–80 % w/w, but its physical form does not deliver the boundary lubrication function required for consistent metal-to-metal die friction reduction. Batch-to-batch phospholipid source variation should be controlled by lipid profiling per USP <621> and oxidative index per Ph. Eur. 2.5.5.