Administration of anti-inflammatory compounds in silastic capsules

Eleven compounds, within hollow capsules of polydimethylsiloxane (Silastic), have been studied with regard to their rate of release and anti-inflammatory activity in the Adjuvant Arthritic (AA) rat. All of the compounds diffused through the capsule wall to some extent with cortisone acetate exhibiting the slowest and ibuprofen the fastest release rate. Of the eleven encapsulated compounds, only phenylbutazone, indomethacin, ibuprofen and naproxen significantly reduced right and left paw volume below that of control value. Silastic encapsulation increases efficacy of phenylbutazone and indomethacin two to three times over subcutaneous or oral administration. Based on potency and duration of constant release, indomethacin and naproxen should exhibit anti-inflammatory activity in excess of 12 months.