Sterile filtration of a parenteral emulsion

The Syntex adjuvant formulation (SAF) containing [thr1]-muramyldipeptide in an oil-in-water emulsion has proven to be an effective adjuvant eliciting both cell-mediated and humoral immune response. As a parenteral emulsion, sterility of the final product was a concern, and various methods of achieving sterility were considered. For emulsions, most conventional sterilization methods are not viable, requiring the more cumbersome technique of sterilizing individual components and assembling/manufacturing under sterile conditions. Emulsion vehicles were manufactured with various models in the Microfluidizer M110 series. All equipment examined was capable of reducing the average dispersed oil droplet size to approximately 160 nm, with varying size ranges. Operating at an internal equipment pressure of greater than 16,000 psi, with at least five cycles through the interaction chamber, the resulting emulsion had a narrow droplet size range distribution, with the largest droplets being small enough to enable sterile filtration. Under specific-manufacturing conditions, the adjuvant emulsion becomes easily filtered through a 0.22-micron cartridge filter, thus yielding a sterile end product. This is the first published example of emulsion sterilization being achieved by terminal filtration.

Formulation of vaccine adjuvant muramyldipeptides. 3. Processing optimization, characterization, and bioactivity of an emulsion vehicle

An efficacious vaccine adjuvant which elicits both cell-mediated immunity (CMI) and humoral immune response was developed using [thr1]-Muramyldipeptide (MDP) in an oil-in-water emulsion vehicle containing poloxamer 401, polysorbate 80, and squalane. Processing optimization was performed to increase the physical stability of this adjuvant emulsion which, when prepared by conventional mixing methods, demonstrated good bioactivity but poor physical stability. Various manufacturing methods were compared with a microfluidization process, which produced the most stable and elegant emulsion vehicle. The microfluidized emulsion also elicited equivalent biological response in the animal model tested.

In vitro and in vivo studies evaluating a liposome system for drug solubilization

A liposome system was developed which demonstrates suitability as an intravenous drug carrier for a lipophilic drug compound (RS-93522, a dihydropyridine CA2+ channel blocker). An aqueous phospholipid suspension was employed as a nontoxic solubilizing vehicle for this drug. The liposome formulation, composed of a 3% mixture of dioleoylphosphatidylcholine and dioleoylphosphatidylglycerol, produced a physically and chemically stable preparation which solubilized the lipophilic drug compound at a concentration 500 times above its intrinsic aqueous solubility. Characterizing the liposome-drug system by gel filtration chromatography showed that the drug comigrated with the lipid constituents of the liposome. Further in vitro studies established that the liposome-RS-93522 formulation allowed for rapid and complete transfer of the drug from the liposome to bind with albumin when added to human serum. In vivo studies with rats were performed in which the pharmacokinetics of the liposomal-RS-93522 system were compared to those of a cosolvent-solubilized RS-93522 solution. This study showed that the pharmacokinetic profiles of the two solutions were identical. All the evidence indicates that a liposome formulation of this type does not alter the distribution of the drug in serum and is, therefore, not likely to affect the intrinsic pharmacological or toxicological parameters of the drug relative to the conventional solvent/excipient-containing formulation. This liposome system demonstrates utility as a biocompatible, nontoxic drug delivery vehicle.

Characterization of the shear sensitivity property of petrolatum

The effects of temperature and mechanical shear on the microcrystalline structure of petrolatum are examined; syneresis determinations and rheological methods are utilized as indicators of the integrity of this structure. Two simple and practical methods for determining the shear sensitivity of petrolatum are presented. The rheological technique of spring relaxation is evaluated and shown to be more valuable than the continuous rheogram data in predicting the microcrystalline structure of petrolatum.