Formulation of stable water-in-oil (w/o) emulsionsystems for parenteral delivery of low pH drugsolutions were investigated. Emulsions wereprepared by hand-shaking and possessed lowviscosities. Sustained in vitro drug release wasachieved with <30% released over 96 h.Additionally, slow release of acid was demonstratedon dilution with PBS, suggesting effectiveencapsulation of the acidic solution within the oilphase. Light microscopy revealed formation of aw/o/w emulsion without significant droplet rupture, atan emulsion/PBS interface. These findings suggestthe oil barrier is maintained on dilution in an aqueousenvironment to reduce both drug and acid release.Hence, irritation potential may be reduced for drugsthat require significant pH adjustment forsolubilization.
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