Proliferation of cultured human fibroblasts and other types of cells has been shown to be hindered by exposure to local anesthetics, which are widely used in musculoskeletal medicine for their use in regional anesthesia, selective nerve blocks, bursography, and brisement. We hypothesized that bupivacaine would decrease cell proliferation and production of extracellular matrix components collagen and proteoglycan in healthy human tenocytes in culture. Primary human tenocyte cultures were prepared from samples of normal tendons obtained from healthy tissue that would otherwise have been discarded during lower extremity tendon transfer surgery. Samples were obtained from 6 patients, 5 women and 1 man with an average age of 69 years (range, 17-73 years). Five flexor digitorum longus tendon samples and 1 peroneus longus tendon sample were used. Harvested tendon tissues (5 mm(3)) were used as explants for primary cell cultures. To measure the proliferative response to bupivacaine, seeded cells were exposed to saline control or to various concentrations of bupivacaine in 1% fetal bovine serum DMEM/F12 or 10% fetal bovine serum DMEM/F12. The 1% fetal bovine serum medium demonstrated the pure bupivacaine effect, and 10% fetal bovine serum more closely approximated the in vivo environment. Seeded cells were starved of fetal bovine serum for 12 hours before exposure to phosphate-buffered saline (control group) and 500 microM bupivacaine (experimental group). This concentration of bupivacaine was selected because it was found to significantly hinder proliferation in both the 1% and 10% fetal bovine serum groups in our proliferation assay. Tenocyte proliferation and extracellular matrix component production were significantly lower (P<or=.05) at >or=1 time points up to 6 days in bupivacaine-treated groups as compared with controls.