Gastrointestinal adverse effects such as esophageal irritation and ulcers are the major disadvantages of the oral administration of alendronate (ALD) and nitrogen-containing bisphosphonate. We hypothesized that the transdermal delivery of ALD via water in oil (w/o) microemulsion might help to prevent the aforementioned side effects without compromising the efficacy. The pseudo-ternary phase diagrams were constructed with varying ratios of surfactant mixture and oil to recognize the concentration range of excipients required to form a monophasic microemulsion. Globule size, morphology transmission electron microscopy, and thermal behavior differential scanning colorimetry of drug-loaded microemulsion were investigated. The in vitro permeation studies revealed significantly enhanced permeation of ALD through microemulsion than pure solution across the rat skin (p < 0.01). In an in vivo pharmacokinetic study in Wistar rats, microemulsion achieved around two folds higher bioavailability than pure drug solution (p < 0.05) when given in equal doses (30 mg/kg). Cell viability assay with human osteoblastic osteosarcoma (MG-63) cells exhibited the positive effects of ALD microemulsion on cell growth. Moreover, alkaline phosphatase and mineralization studies proved that microemulsion as a carrier retains distinct osteogenic properties of ALD. Overall, these outcomes demonstrated that the w/o microemulsion as a transdermal carrier is a promising approach for the effective delivery of ALD, bypassing the adverse effects associated with oral administration.
Key words: Osteoporosis, bone, transdermal, microemulsion, osteogenic, alendronate
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