Abstract. Piperazinylalkyl ester prodrugs (4a-5d) of 6-methoxy-2-naphthylacetic acid (6-MNA) (1) were synthesized and evaluated in vitro for the purpose of percutaneous drug delivery. These ionizable prodrugs exhibited varying aqueous solubilities and lipophilicities depending on the pH of the medium. The prodrugs (4a-5c) showed higher aqueous solubility and similar lipophilicity at pH 5.0 and lower aqueous solubility and higher lipophilicity at pH 7.4 in comparison to 6-MNA. The chemical and enzymatic hydrolyses of the prodrugs was investigated in aqueous buffer solutions (pH 5.0 and 7.4) and in 80% human serum (pH 7.4) at 37°C. The prodrugs showed moderate chemical stability (t 1/2 =6-60 h) but got readily hydrolyzed enzymatically to 6-MNA with half-life ranging from 10-60 min. In the in vitro permeation study using rat skin, the flux of 6-MNA and the prodrugs was determined in aqueous buffers of pH 5.0 and 7.4. The prodrug (5b) showed 7.9-and 11.2-fold enhancement in skin permeation compared to 6-MNA (1) at pH 5.0 and 7.4, respectively. It was concluded that the parent NSAIDs having favorable pharmacokinetic and pharmacodynamic properties coupled with increased skin permeability of their prodrugs could give better options for the treatment of rheumatic diseases.

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Arthritis is a heterogeneous group of conditions that leads to joint symptoms and signs which are associated with defective integrity of articular cartilage. Major classes of drugs which are widely used for the treatment of arthritis are Non-Steroidal Anti-inflammatory Drugs (NSAIDs). Development of an efficient means of percutaneous delivery can increase drug concentration in local soft-tissues and joints while reducing the systemic distribution of a drug and its side effects. The present work is aimed at synthesisand evaluation of prodrugs of some NSAIDs for percutaneous drug delivery for the treatment of arthritis.