An aqueous hot melted type adhesive base material containing 4-biphenylyl acetic acid (BPAA) is provided. The adhesive base material contains constant amounts of BPAA and has good drug releasability, so that bioavailability of the drug is enhanced. An analgesic and anti-inflammatory external plaster containing BPAA is also provided. The plaster is obtained by dissolving BPAA into an aqueous hot melted type adhesive base material comprising as essential components a styrene-isoprene-styrene block copolymer, an adhesive resin, an antioxidant, lanolin, and water.